This document presents new experimental results on critical phenomena in solid solutions at low impurity concentrations. It was observed that the X-ray diffraction linewidth decreases anomalously, while the lattice thermal conductivity and heat capacity increase in the impurity concentration range below 1.0 atomic percent in some ternary solid solutions based on IV-VI semiconducting compounds. These experimental results are analyzed using percolation theory and the theory of second-order phase transitions. It is suggested that self-organization processes of impurity atoms accompany the percolation phenomena. The results provide further evidence that critical phenomena occur universally when transitioning from an impurity discontinuum to an impurity continuum in solid solutions.
This document summarizes the mechanochemical synthesis of isoreticular metal-organic frameworks (IRMOFs) and their potential for nitrobenzene sensing. Specifically, it discusses:
1) The liquid-assisted grinding synthesis of IRMOF-1 and halogen-substituted IRMOF-2 frameworks containing chlorine, bromine, or iodine.
2) Characterization of the frameworks by powder X-ray diffraction and scanning electron microscopy, which confirmed their structures.
3) Investigation of the frameworks' fluorescence properties, which revealed IRMOF-1 is a highly sensitive and selective fluorescence quenching agent for nitrobenzene detection.
4) The role of
Structural and magnetic properties on F-doped LiVO2 with two-dimensional tria...Yang Li
The layered oxide LiVO2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO2 samples, and reported the F-doping effect on the structure and transition temperature Tt. The samples LiVO2-xFx (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature Tt increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO6 block in structure, which significantly influence the magnetic ordering transition temperature Tt.
This document describes a study using integral equation theory and Monte Carlo simulation to determine the structure and thermodynamics of a colloidal solution where particles interact via Yukawa or Sogami potentials. The authors use the hybridized mean spherical approximation within the integral equation theory to calculate properties like the pair correlation function, structure factor, internal energy and pressure. They find good quantitative agreement between results from integral equation theory using a Sogami potential and results from Monte Carlo simulation. The theoretical results are also compared to experimental data and show agreement when using a Sogami potential.
Correlation between corrosion inhibitive effect and quantum molecular structu...Al Baha University
This document summarizes a study that used quantum chemical calculations to analyze the molecular structures and inhibition efficiencies of five Schiff base compounds as corrosion inhibitors for iron in acidic and alkaline solutions. The study calculated parameters like frontier molecular orbital energies, charge distribution, electronegativity, electron transfer, dipole moment, and total energy and correlated them with inhibition efficiencies observed experimentally. The results showed that inhibition efficiency increased with higher highest occupied molecular orbital energy and lower energy gap between lowest unoccupied and highest occupied molecular orbitals. Adsorption of the inhibitor molecules on the iron surface is believed to inhibit corrosion by blocking reaction sites and donating electrons through interactions involving nitrogen and oxygen atoms and aromatic rings. The inhibition efficiency followed the order Schiff
CRYSTALLOGRAPHIC AND MORPHOLOGICAL STUDY OF SODIUM ZIRCONIUM PHOSPHATE AS A H...EDITOR IJCRCPS
Sodium zirconium phosphate (NZP) is a potential material for immobilization of nuclear effluents. The Structure of polycrystalline
phase of barium containing NZP was determined on the basis of crystal data of solid state simulated waste forms. The crystal
structure of Na1-xBax/2Zr2P3O12 (x=0.1-1.0) has been investigated using General Structure Analysis System (GSAS) programming.
The BaNZP phase crystallizes in the space group R-3c and Z=6. Powder diffraction data have been subjected to Rietveld
refinement to arrive at a satisfactory structural convergence of R-factors. The unit cell volume and polyhedral (ZrO6 and PO4)
distortion increases with rise in the mole % of Ba2+ in the NZP matrix. SEM, TEM and EDX analysis provide analytical evidence of
barium in the matrix.
Keywords: Ceramic; powder XRD; Rietveld refinement; SEM; nuclear waste immobilization.
DETONATION AND COMBUSTION OF NEW HETEROGENEOUS COMPOSITE EXPLOSIVES CONTAININ...Robert Weinheimer
A water free slurry method for explosive flegmatization and multi-components rich-fuel macroscopic granules preparation was elaborated with success. Confined explosion investigations showed that the structure of the
macroscopic granular composite, charge type, aluminium particle sizes and oxygen availability inside the explosion chamber affect strongly the QSP and the aluminium after-burning reactions in the confined space.
Geometrical isomerism refers to structural isomers that differ in the orientation of functional groups around a double bond or ring structure. There are three main systems used to name geometrical isomers: cis-trans, E-Z, and syn-anti. Cis-trans nomenclature refers to whether identical groups are on the same side (cis) or opposite sides (trans) of a double bond. E-Z nomenclature is used when all four substituents are different. Syn-anti refers to whether substituents are on the same side (syn) or opposite sides (anti) of a carbon-nitrogen double bond. Various methods can be used to determine the configuration of geometrical is
The document summarizes a study of magnetite nanoparticles prepared by a modified Massart method using water and alcohol as solvents. Three key findings are:
1) Nanoparticles prepared in alcohol were smaller (8 nm) than those in water (12-13 nm) according to TEM analysis.
2) Longer reaction times improved the stoichiometry of the nanoparticles, as seen by an increasing β ratio in Mossbauer spectra.
3) The transition to superparamagnetic behavior occurred around 8 nm for magnetite nanoparticles coated with TBAOH, as evidenced by changes in Mossbauer spectra.
This document summarizes the mechanochemical synthesis of isoreticular metal-organic frameworks (IRMOFs) and their potential for nitrobenzene sensing. Specifically, it discusses:
1) The liquid-assisted grinding synthesis of IRMOF-1 and halogen-substituted IRMOF-2 frameworks containing chlorine, bromine, or iodine.
2) Characterization of the frameworks by powder X-ray diffraction and scanning electron microscopy, which confirmed their structures.
3) Investigation of the frameworks' fluorescence properties, which revealed IRMOF-1 is a highly sensitive and selective fluorescence quenching agent for nitrobenzene detection.
4) The role of
Structural and magnetic properties on F-doped LiVO2 with two-dimensional tria...Yang Li
The layered oxide LiVO2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO2 samples, and reported the F-doping effect on the structure and transition temperature Tt. The samples LiVO2-xFx (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature Tt increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO6 block in structure, which significantly influence the magnetic ordering transition temperature Tt.
This document describes a study using integral equation theory and Monte Carlo simulation to determine the structure and thermodynamics of a colloidal solution where particles interact via Yukawa or Sogami potentials. The authors use the hybridized mean spherical approximation within the integral equation theory to calculate properties like the pair correlation function, structure factor, internal energy and pressure. They find good quantitative agreement between results from integral equation theory using a Sogami potential and results from Monte Carlo simulation. The theoretical results are also compared to experimental data and show agreement when using a Sogami potential.
Correlation between corrosion inhibitive effect and quantum molecular structu...Al Baha University
This document summarizes a study that used quantum chemical calculations to analyze the molecular structures and inhibition efficiencies of five Schiff base compounds as corrosion inhibitors for iron in acidic and alkaline solutions. The study calculated parameters like frontier molecular orbital energies, charge distribution, electronegativity, electron transfer, dipole moment, and total energy and correlated them with inhibition efficiencies observed experimentally. The results showed that inhibition efficiency increased with higher highest occupied molecular orbital energy and lower energy gap between lowest unoccupied and highest occupied molecular orbitals. Adsorption of the inhibitor molecules on the iron surface is believed to inhibit corrosion by blocking reaction sites and donating electrons through interactions involving nitrogen and oxygen atoms and aromatic rings. The inhibition efficiency followed the order Schiff
CRYSTALLOGRAPHIC AND MORPHOLOGICAL STUDY OF SODIUM ZIRCONIUM PHOSPHATE AS A H...EDITOR IJCRCPS
Sodium zirconium phosphate (NZP) is a potential material for immobilization of nuclear effluents. The Structure of polycrystalline
phase of barium containing NZP was determined on the basis of crystal data of solid state simulated waste forms. The crystal
structure of Na1-xBax/2Zr2P3O12 (x=0.1-1.0) has been investigated using General Structure Analysis System (GSAS) programming.
The BaNZP phase crystallizes in the space group R-3c and Z=6. Powder diffraction data have been subjected to Rietveld
refinement to arrive at a satisfactory structural convergence of R-factors. The unit cell volume and polyhedral (ZrO6 and PO4)
distortion increases with rise in the mole % of Ba2+ in the NZP matrix. SEM, TEM and EDX analysis provide analytical evidence of
barium in the matrix.
Keywords: Ceramic; powder XRD; Rietveld refinement; SEM; nuclear waste immobilization.
DETONATION AND COMBUSTION OF NEW HETEROGENEOUS COMPOSITE EXPLOSIVES CONTAININ...Robert Weinheimer
A water free slurry method for explosive flegmatization and multi-components rich-fuel macroscopic granules preparation was elaborated with success. Confined explosion investigations showed that the structure of the
macroscopic granular composite, charge type, aluminium particle sizes and oxygen availability inside the explosion chamber affect strongly the QSP and the aluminium after-burning reactions in the confined space.
Geometrical isomerism refers to structural isomers that differ in the orientation of functional groups around a double bond or ring structure. There are three main systems used to name geometrical isomers: cis-trans, E-Z, and syn-anti. Cis-trans nomenclature refers to whether identical groups are on the same side (cis) or opposite sides (trans) of a double bond. E-Z nomenclature is used when all four substituents are different. Syn-anti refers to whether substituents are on the same side (syn) or opposite sides (anti) of a carbon-nitrogen double bond. Various methods can be used to determine the configuration of geometrical is
The document summarizes a study of magnetite nanoparticles prepared by a modified Massart method using water and alcohol as solvents. Three key findings are:
1) Nanoparticles prepared in alcohol were smaller (8 nm) than those in water (12-13 nm) according to TEM analysis.
2) Longer reaction times improved the stoichiometry of the nanoparticles, as seen by an increasing β ratio in Mossbauer spectra.
3) The transition to superparamagnetic behavior occurred around 8 nm for magnetite nanoparticles coated with TBAOH, as evidenced by changes in Mossbauer spectra.
Journal of the Taiwan Institute of Chemical Engineers 0 0 0 (2016) 1–20Al Baha University
Quantum chemical calculations, molecular dynamics simulation and experimental studies of using some azo dyes as corrosion inhibitors for iron. Part 1: Mono-azo dye derivatives
This document summarizes research on fractionating and characterizing naturally occurring organo-clay complexes. It discusses techniques used for physical and chemical fractionation as well as characterization methods like NMR, XRD, TEM, SEM, and thermal analysis. Key findings are presented on the effect of tillage on complex stability and composition differences between rhizosphere and non-rhizosphere complexes. The conclusion indicates techniques like DXRD and NMR provided new insights while TEM/SEM images helped identify clay minerals. Further research on natural versus synthetic complexes and microbial impacts was recommended.
Spectral studies of 5-({4-amino-2-[(Z)-(2-hydroxybenzylidene) amino] pyrimidi...IOSR Journals
Some transition metal ions Complexes with 5-({4-amino-2-[(Z)-(2-hydroxybenzylidene) amino]
pyrimidin-5-yl} methyl)-2,3,4-trimethoxybenzene were prepared and characterized by elemental analyses,
Infrared , magnetic moment, electronic spectra , mass spectra, X-ray powder diffraction, molar conductance
and thermal analysis (TGA). The complexes have general formulae [ML2.2H2O] {where M = Mn (II), Co (II), Ni
(II), Cu (II), Zn (II), Pd (II) and Pt (II). The coordination behavior of the metal ions towards to the investigated
Schiff base takes place through –C=N,-NH2 and –OH groups. The obtained C, H and N elemental analysis data
showed the Metal: Ligand ratio is 1:2 [M: L] ratio. The molar conductance data reveal that all the metal
complexes are non-electrolytic in nature. From the magnetic moments the complexes are paramagnetic except
Zn metal ion complexes have octahedral geometry with coordination number eight. The thermal behavior of
these complexes shows that, the hydrated complexes have loses two water molecules and immediately followed
by decomposition of the anions and ligand molecules in the second and third stage. The Schiff bases and metal
complexes show good activity against some bacteria. The antimicrobial results indicate that, the metal
complexes have better antimicrobial activity as compared to the prepared Schiff base.
This document describes the synthesis, spectral characterization, and biological screening of transition metal complexes of the ligand 2-(5-mercapto-1,3,4-oxadiazol-2-yl)phenol. A series of complexes were prepared using Cu(II), Co(II), Ni(II), and Zn(II) and characterized using analytical data, magnetic susceptibility, IR, UV-Vis, 1H NMR, 13C NMR, EPR, and other techniques. Spectral data suggest an octahedral geometry around the metal ion. Biological screening showed the complexes have antibacterial, antifungal, and DNA cleavage activities.
Structural and Dielectric Properties of Lanthanum Substituted Lead ZirconateT...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Sandrogreco Tautomeric Equilibria In Relation To Pi Electron DelocalizationProfª Cristiana Passinato
This document provides an overview of tautomeric equilibria and its importance in natural science and life. It begins with an introduction that discusses how tautomerism plays an important role in organic chemistry, biochemistry, and life processes. It then discusses the historical background and definitions of tautomerism, varieties of prototropic frameworks, mechanisms of prototropic interconversions, methods for estimating equilibrium constants, and quantitative measures of electron delocalization. The document reviews specific examples of tautomeric equilibria in open chain molecules, aromatic systems, natural products, and concludes with a discussion of the importance and applications of understanding tautomerism.
The document discusses computational approaches for predicting the toxicity of nanomaterials. It provides background on the increasing presence of nanomaterials in consumer products and objectives to understand their toxicological properties. Descriptors for quantitative structure-activity relationship (QSAR) modeling are discussed, including the size, surface area, composition and shape of nanoparticles. Examples are given of using QSAR to model the solubility of fullerenes and carbon nanotubes, and to develop preliminary models for the toxicity of metal oxides to E. coli bacteria. The challenges of adapting traditional computational toxicology methods to nanoparticles are also addressed.
Influence of the alkyl chain length of alkyltriazoles on the corrosion inhibi...Al Baha University
Abstract. Steel is an important material and has been widely used in today's industrial production. Using organic
corrosion inhibitors is an effective means to prevent steel from corrosion. Generally, the molecular structures of
inhibitors can have a major impact on their corrosion inhibition efficiency. In this work, the influence of alkyl chain
length of three alkyltriazoles on the corrosion inhibition of iron has been investigated by density functional based tight
binding (DFTB) approach. Several typical descriptors such as frontier molecular orbital, adsorption energy, density of
states have been discussed in detail. Our findings will contribute to the understanding of the inhibition mechanism and
the designing of novel corrosion inhibitors.
Spectroscopic, Thermal, Magnetic and conductimetric studies on some 7-hydroxy...IOSR Journals
7-hydroxy-4-methyl-8-(p-methylphenylazo)coumarin (L1) and 7-hydroxy-4-methyl-8-(p-methoxyphenylazo)coumarin (L2) have been prepared and characterized by elemental analysis, infrared (IR), proton nuclear magnetic resonance (1H NMR) and mass spectra. The important infrared (IR) spectral bands corresponding to the active groups in the two ligands and the solid complexes under investigation were studied. Also the important fragments in the ligands and complexes were done using mass spectra and the main peaks were corresponding to the molecular weights of the ligands and complexes. The solid complexes have been synthesized and characterized by elemental and thermal analyses (TG and DTA) as well as by IR, 1H NMR, magnetic measurements, electronic transition, molar conductance, mass and electron spin resonance (ESR) spectra. The proposed steriochemical structures for the investigated metal complexes suggest octahedral geometry with respect to Mn, Co, Ni, Cu and Zn divalent metal ions with the investigated ligands 1:1 and 1:2 complexes and all of the formed complexes contain coordinated and hydrated water molecules. All of the prepared solid complexes behave as non-electrolytes in chloroform.
The effect of hygroscopic growth on urban aerosolsAlexander Decker
This document discusses the effect of hygroscopic growth on urban aerosols. It extracts microphysical and optical properties from an aerosol database to determine the impact of water uptake at various relative humidities. Growth factors and enhancement parameters are determined from the properties and parameterized using models. Angstrom coefficients are used to characterize the particle size distribution. The mixture is found to have a bimodal distribution dominated by fine mode particles. Hygroscopic growth follows parameterization models well, with growth factors ranging from 1.01 to 1.08 as humidity increases from 50% to 99%.
Vibrational Characterization and Antioxidant Activity of Newly Synthesized Ga...peertechzpublication
The gallium(III) complex of orotic acid (HOA) was synthesized and its structure was determined
by means of analytical and spectral analyses. Detailed vibrational analysis of HOA, sodium salt of HOA
(NaOA) and Ga(III)-OA systems based on both the calculated and experimental spectra confi rmed the
suggested metal-ligand binding mode. Signifi cant differences in the IR and Raman spectra of the complex
were observed as compared to the spectra of the ligand and confi rmed the suggested metal-ligand
binding mode.
This study investigates the corrosion inhibition of iron by six mono-azo dye derivatives (MAD_1-6) in 2M HNO3 and 2M NaOH solutions using experimental and computational methods. Gravimetric, thermometric, UV-Vis spectrophotometric, and electrochemical polarization techniques were used to determine inhibition efficiencies experimentally. Density functional theory calculations and molecular dynamics simulations were performed to calculate quantum chemical parameters and binding energies on the Fe(110) surface. Theoretical data agreed well with experimental inhibition efficiencies, with MAD_1 and MAD_6 showing the best inhibition in acidic and alkaline solutions, respectively.
Bioadsorption of Pb2+ and Cu2+ on Eucalyptus Camaldulensis LeavesIJEAB
Herein, the efficiency of Eucalyptus camaldulensis leaves as biosorbent for lead and copper was investigated. The particle size distribution was determined by Granulometric analysis and the functional groups were identified by FT-IR spectroscopy. The effects of contact time, pH and initial metal ions concentration were investigated. The experimental kinetic data were well fitted by the pseudo-second order kinetic model and Langmuir isotherm with a maximum adsorption capacity up to 71 mg g-1 and 37 mg g-1 for Cu2+ and Pb2+ respectively. The selectivity was examined in a binary ions solution where the adsorbent showed preference for lead over copper.
Thermodynamics and adsorption studies of rhodamine-b dye onto organoclayInnspub Net
Thermodynamics and adsorption studies were conducted with a dye of Rhoda mine-B (RB) on organoclay (OC). Adsorption of the dye was investigated with an initial dye concentration at pH 7±0.3, 298, 308 and 318 K. The adsorption experiments were carried out isothermally at three different temperatures. The Langmuir and Freundlich isotherm models were used to describe the equilibrium data and the results were discussed in details. The thermodynamic parameters such as standard free energy (∆G°), entropy change (∆S°) and enthalpy (∆H°) were calculated for OC. These values showed that adsorption of RB on OC was a spontaneous and endothermic process.
This document describes the synthesis and characterization of two new lanthanide-based metal-organic frameworks (MOFs) using pamoic acid as the organic ligand. Single crystal X-ray diffraction shows that the MOFs form three-dimensional frameworks with channels of different sizes depending on the lanthanide ion (Gd3+ or Dy3+). Magnetic measurements reveal one MOF acts as a cryogenic magnetic refrigerant while the other shows slow relaxation of magnetization. Adsorption studies show the MOFs selectively uptake CO2 over other gases and have high methanol vapor uptake. Photoluminescence properties indicate the MOFs are also photoluminescent materials.
Overview of means & methods used in structural elucidation of natural products. Presentation Topic Given by Faculty, It is compulsory because for this we are having our internal marks.
Coordination modes of a new ligand derived from pyrazoline with cr(iii), mn(i...Alexander Decker
This document summarizes a study that synthesized and characterized coordination complexes of Cr(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions with a new ligand derived from pyrazoline. The complexes were analyzed using various techniques including elemental analysis, infrared spectroscopy, NMR spectroscopy, magnetic susceptibility measurements, and electronic spectroscopy. The data indicated the ligand behaves as a neutral bidentate toward the metal ions. The biological activities of the ligand and its complexes were screened against bacteria and fungi, with some complexes showing higher antimicrobial activity than the free ligand.
A Hierarchical Model for the Analysis of Scattering Data of Complex MaterialsAkinola Oyedele
Interpreting the results of scattering data for complex materials with hierarchical structure in which at least one of the phases is amorphous often relies upon the use of large-scale molecular dynamics (MD) simulations, in which a structure is hypothesized and from which a radial distribution function (RDF) can be extracted and directly compared with experiment. This computationally intensive approach presents a bottleneck in the efficient characterization of the atomic structure of new materials. Here, we demonstrate an approach based on a hierarchical decomposition of the RDF from a combination of tractable models and theory at the atomic and meso- scales, which
when combined yield the RDF. We apply the procedure to a carbon composite and compare the model with the RDF from both MD simulation and neutron scattering.
This document discusses photoluminescence studies of Eu3+ doped La0.6Y0.4PO4 phosphor codoped with Tb3+ and Gd3+. The phosphors were prepared by solid state diffusion reaction and characterized using XRD, SEM, and photoluminescence techniques. XRD analysis confirmed the monoclinic crystal structure. SEM images showed irregularly shaped particles ranging from submicron to microns in size. Photoluminescence emission was observed from 530-630 nm under 254 nm excitation. Codoping with Tb3+ and Gd3+ increased the intensity of the 612 nm emission peak from the Eu3+ ions, likely due to a cross relaxation
Studies On The Cobalt(II) And Copper(II) Complexes Of 2,5-Substituted 1,3,4-T...IOSR Journals
1. New metal complexes of Co(II) and Cu(II) were synthesized by reacting solutions of the metal salts with 2,5-substituted 1,3,4-triazole ligands in an alcoholic medium.
2. The complexes were characterized through techniques such as elemental analysis, magnetic susceptibility, molar conductance, and IR spectroscopy.
3. Based on analytical data and characterization, the complexes were determined to have a 1:2 metal to ligand ratio and the ligand was found to act as a bidentate ligand coordinating through nitrogen atoms in the ring.
En España hay tres tipos principales de sectores industriales: sectores maduros con baja tecnología, sectores más dinámicos con presencia extranjera como automóvil y química, y sectores de alta tecnología como informática e instrumentos ópticos. El empleo industrial ha disminuido recientemente con 55,500 puestos de trabajo perdidos. Endesa es una de las tres mayores empresas eléctricas en España y genera más de 10 mil millones de euros anuales.
Journal of the Taiwan Institute of Chemical Engineers 0 0 0 (2016) 1–20Al Baha University
Quantum chemical calculations, molecular dynamics simulation and experimental studies of using some azo dyes as corrosion inhibitors for iron. Part 1: Mono-azo dye derivatives
This document summarizes research on fractionating and characterizing naturally occurring organo-clay complexes. It discusses techniques used for physical and chemical fractionation as well as characterization methods like NMR, XRD, TEM, SEM, and thermal analysis. Key findings are presented on the effect of tillage on complex stability and composition differences between rhizosphere and non-rhizosphere complexes. The conclusion indicates techniques like DXRD and NMR provided new insights while TEM/SEM images helped identify clay minerals. Further research on natural versus synthetic complexes and microbial impacts was recommended.
Spectral studies of 5-({4-amino-2-[(Z)-(2-hydroxybenzylidene) amino] pyrimidi...IOSR Journals
Some transition metal ions Complexes with 5-({4-amino-2-[(Z)-(2-hydroxybenzylidene) amino]
pyrimidin-5-yl} methyl)-2,3,4-trimethoxybenzene were prepared and characterized by elemental analyses,
Infrared , magnetic moment, electronic spectra , mass spectra, X-ray powder diffraction, molar conductance
and thermal analysis (TGA). The complexes have general formulae [ML2.2H2O] {where M = Mn (II), Co (II), Ni
(II), Cu (II), Zn (II), Pd (II) and Pt (II). The coordination behavior of the metal ions towards to the investigated
Schiff base takes place through –C=N,-NH2 and –OH groups. The obtained C, H and N elemental analysis data
showed the Metal: Ligand ratio is 1:2 [M: L] ratio. The molar conductance data reveal that all the metal
complexes are non-electrolytic in nature. From the magnetic moments the complexes are paramagnetic except
Zn metal ion complexes have octahedral geometry with coordination number eight. The thermal behavior of
these complexes shows that, the hydrated complexes have loses two water molecules and immediately followed
by decomposition of the anions and ligand molecules in the second and third stage. The Schiff bases and metal
complexes show good activity against some bacteria. The antimicrobial results indicate that, the metal
complexes have better antimicrobial activity as compared to the prepared Schiff base.
This document describes the synthesis, spectral characterization, and biological screening of transition metal complexes of the ligand 2-(5-mercapto-1,3,4-oxadiazol-2-yl)phenol. A series of complexes were prepared using Cu(II), Co(II), Ni(II), and Zn(II) and characterized using analytical data, magnetic susceptibility, IR, UV-Vis, 1H NMR, 13C NMR, EPR, and other techniques. Spectral data suggest an octahedral geometry around the metal ion. Biological screening showed the complexes have antibacterial, antifungal, and DNA cleavage activities.
Structural and Dielectric Properties of Lanthanum Substituted Lead ZirconateT...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Sandrogreco Tautomeric Equilibria In Relation To Pi Electron DelocalizationProfª Cristiana Passinato
This document provides an overview of tautomeric equilibria and its importance in natural science and life. It begins with an introduction that discusses how tautomerism plays an important role in organic chemistry, biochemistry, and life processes. It then discusses the historical background and definitions of tautomerism, varieties of prototropic frameworks, mechanisms of prototropic interconversions, methods for estimating equilibrium constants, and quantitative measures of electron delocalization. The document reviews specific examples of tautomeric equilibria in open chain molecules, aromatic systems, natural products, and concludes with a discussion of the importance and applications of understanding tautomerism.
The document discusses computational approaches for predicting the toxicity of nanomaterials. It provides background on the increasing presence of nanomaterials in consumer products and objectives to understand their toxicological properties. Descriptors for quantitative structure-activity relationship (QSAR) modeling are discussed, including the size, surface area, composition and shape of nanoparticles. Examples are given of using QSAR to model the solubility of fullerenes and carbon nanotubes, and to develop preliminary models for the toxicity of metal oxides to E. coli bacteria. The challenges of adapting traditional computational toxicology methods to nanoparticles are also addressed.
Influence of the alkyl chain length of alkyltriazoles on the corrosion inhibi...Al Baha University
Abstract. Steel is an important material and has been widely used in today's industrial production. Using organic
corrosion inhibitors is an effective means to prevent steel from corrosion. Generally, the molecular structures of
inhibitors can have a major impact on their corrosion inhibition efficiency. In this work, the influence of alkyl chain
length of three alkyltriazoles on the corrosion inhibition of iron has been investigated by density functional based tight
binding (DFTB) approach. Several typical descriptors such as frontier molecular orbital, adsorption energy, density of
states have been discussed in detail. Our findings will contribute to the understanding of the inhibition mechanism and
the designing of novel corrosion inhibitors.
Spectroscopic, Thermal, Magnetic and conductimetric studies on some 7-hydroxy...IOSR Journals
7-hydroxy-4-methyl-8-(p-methylphenylazo)coumarin (L1) and 7-hydroxy-4-methyl-8-(p-methoxyphenylazo)coumarin (L2) have been prepared and characterized by elemental analysis, infrared (IR), proton nuclear magnetic resonance (1H NMR) and mass spectra. The important infrared (IR) spectral bands corresponding to the active groups in the two ligands and the solid complexes under investigation were studied. Also the important fragments in the ligands and complexes were done using mass spectra and the main peaks were corresponding to the molecular weights of the ligands and complexes. The solid complexes have been synthesized and characterized by elemental and thermal analyses (TG and DTA) as well as by IR, 1H NMR, magnetic measurements, electronic transition, molar conductance, mass and electron spin resonance (ESR) spectra. The proposed steriochemical structures for the investigated metal complexes suggest octahedral geometry with respect to Mn, Co, Ni, Cu and Zn divalent metal ions with the investigated ligands 1:1 and 1:2 complexes and all of the formed complexes contain coordinated and hydrated water molecules. All of the prepared solid complexes behave as non-electrolytes in chloroform.
The effect of hygroscopic growth on urban aerosolsAlexander Decker
This document discusses the effect of hygroscopic growth on urban aerosols. It extracts microphysical and optical properties from an aerosol database to determine the impact of water uptake at various relative humidities. Growth factors and enhancement parameters are determined from the properties and parameterized using models. Angstrom coefficients are used to characterize the particle size distribution. The mixture is found to have a bimodal distribution dominated by fine mode particles. Hygroscopic growth follows parameterization models well, with growth factors ranging from 1.01 to 1.08 as humidity increases from 50% to 99%.
Vibrational Characterization and Antioxidant Activity of Newly Synthesized Ga...peertechzpublication
The gallium(III) complex of orotic acid (HOA) was synthesized and its structure was determined
by means of analytical and spectral analyses. Detailed vibrational analysis of HOA, sodium salt of HOA
(NaOA) and Ga(III)-OA systems based on both the calculated and experimental spectra confi rmed the
suggested metal-ligand binding mode. Signifi cant differences in the IR and Raman spectra of the complex
were observed as compared to the spectra of the ligand and confi rmed the suggested metal-ligand
binding mode.
This study investigates the corrosion inhibition of iron by six mono-azo dye derivatives (MAD_1-6) in 2M HNO3 and 2M NaOH solutions using experimental and computational methods. Gravimetric, thermometric, UV-Vis spectrophotometric, and electrochemical polarization techniques were used to determine inhibition efficiencies experimentally. Density functional theory calculations and molecular dynamics simulations were performed to calculate quantum chemical parameters and binding energies on the Fe(110) surface. Theoretical data agreed well with experimental inhibition efficiencies, with MAD_1 and MAD_6 showing the best inhibition in acidic and alkaline solutions, respectively.
Bioadsorption of Pb2+ and Cu2+ on Eucalyptus Camaldulensis LeavesIJEAB
Herein, the efficiency of Eucalyptus camaldulensis leaves as biosorbent for lead and copper was investigated. The particle size distribution was determined by Granulometric analysis and the functional groups were identified by FT-IR spectroscopy. The effects of contact time, pH and initial metal ions concentration were investigated. The experimental kinetic data were well fitted by the pseudo-second order kinetic model and Langmuir isotherm with a maximum adsorption capacity up to 71 mg g-1 and 37 mg g-1 for Cu2+ and Pb2+ respectively. The selectivity was examined in a binary ions solution where the adsorbent showed preference for lead over copper.
Thermodynamics and adsorption studies of rhodamine-b dye onto organoclayInnspub Net
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Overview of means & methods used in structural elucidation of natural products. Presentation Topic Given by Faculty, It is compulsory because for this we are having our internal marks.
Coordination modes of a new ligand derived from pyrazoline with cr(iii), mn(i...Alexander Decker
This document summarizes a study that synthesized and characterized coordination complexes of Cr(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions with a new ligand derived from pyrazoline. The complexes were analyzed using various techniques including elemental analysis, infrared spectroscopy, NMR spectroscopy, magnetic susceptibility measurements, and electronic spectroscopy. The data indicated the ligand behaves as a neutral bidentate toward the metal ions. The biological activities of the ligand and its complexes were screened against bacteria and fungi, with some complexes showing higher antimicrobial activity than the free ligand.
A Hierarchical Model for the Analysis of Scattering Data of Complex MaterialsAkinola Oyedele
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En España hay tres tipos principales de sectores industriales: sectores maduros con baja tecnología, sectores más dinámicos con presencia extranjera como automóvil y química, y sectores de alta tecnología como informática e instrumentos ópticos. El empleo industrial ha disminuido recientemente con 55,500 puestos de trabajo perdidos. Endesa es una de las tres mayores empresas eléctricas en España y genera más de 10 mil millones de euros anuales.
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Preformulation testing of solid dosage formsGaurav Kr
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Dislocation occurs when a joint is displaced and the supporting ligaments and joint capsule are disrupted. There are different types including congenital, acquired, traumatic, and pathological dislocations. The most common joints that dislocate are the shoulder, hip, elbow, fingers, and cervical facet joints. Investigations include x-rays from different angles and sometimes CT scans. Management involves reducing acute dislocations promptly through closed reduction under anesthesia if possible to avoid complications like nerve damage, recurrent dislocations, and arthritis. Different techniques are used for reducing specific joints like the shoulder, hip, and fingers. Immobilization after reduction helps prevent recurrence.
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This document discusses various types of crystal defects including point defects, linear defects (dislocations), and planar defects. It explains that plastic deformation occurs due to the movement of dislocations along specific crystallographic planes and directions known as slip systems. Face-centered cubic metals have 12 possible slip systems comprising the {111} family of planes and <110> directions within each plane. Body-centered cubic and hexagonal close-packed metals also have defined slip systems that allow plastic deformation through dislocation movement.
Strength to Weight Ratio is an important factor in this design.
Aluminum has a higher Strength to Weight Ratio than steel, making it lighter. However, polymers like polyethylene are even lighter than aluminum and can be easily molded.
While both aluminum and polyethylene meet the design requirements, polyethylene is lower in cost and lighter. Therefore, polyethylene would be the best choice of material for the soda drink container design. Its light weight, high strength, corrosion resistance and low manufacturing cost make it suitable to produce large volumes of containers economically.
Calculation of lattice thermal expansion coefficient of RBO4 (R=lanthanides, ...IRJET Journal
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This document summarizes a theoretical study of a two-species Bose-Einstein condensate loaded into an optical lattice. The study finds that quantum fluctuations destroy long-range coherence between atoms in different lattice sites. For miscible atoms, fluctuations reduce inter- and intra-species coherence and on-site atom number fluctuations. For immiscible atoms, fluctuations enhance number fluctuations, reduce coherence, and cause spontaneous formation of interleaved spatial domains of each species with fluctuating domain lengths depending on quantum effects.
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This document discusses the properties and reactivity of nanoparticles for catalysis applications. It notes that nanoparticles have a high surface area to volume ratio, which allows them to be more reactive. The physical and electronic properties, including reactivity, of particles varies significantly as size is reduced to the nanoscale. Studies have shown that properties like chemisorption and catalytic activity depend on particle size and number of atoms. The reactivity of very small clusters, even when supported, relates to their distinct electronic structure based on atom number. Particle shape, support interactions, and alloy composition also influence catalytic properties at the nanoscale.
Interaction of Components in Molecular Optoelectronics for the Next Generati...Scientific Review SR
The interaction of molecular optoelectronic components on the molecular scale were studied where
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far-reaching interactions of electronically excited structures until macroscopic dimensions were fond and may be
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Probing spin dynamics from the Mott insulating to the superfluid regime in a ...Arijit Sharma
This document summarizes an experiment probing spin dynamics in a dipolar atomic Bose gas across the Mott insulating to superfluid transition in an optical lattice. Three key findings are:
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This document summarizes a numerical study of the structure and thermodynamics of colloidal suspensions using the variational method and integral equation theory. The interactions between colloid particles are modeled using either a Yukawa or Sogami potential. Results from the integral equation theory using a Sogami potential are found to be in good agreement with Monte Carlo simulation results and experimental data. The variational method and integral equation theory are used to calculate structural properties like the pair correlation function and thermodynamic properties.
Physical Characterization of a Method for Production of High Stability Suspen...Editor IJCATR
Suspensions/Dispersions are encountered in a wide range of
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A study the effect of zr o3 on the electrical and mechanical propertiesAlexander Decker
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Proceedings of the American Society for Composites 2009-Twenty-Fourth Technical ConferenceWith the Canadian Association for Composite Structures and Materials (Joint Canadian-American International Conference), September 15-17, Newark, DE
Similar to 2003 self-organization processes in impurity subsystem of solid solutions (20)
2003 self-organization processes in impurity subsystem of solid solutions
1. Journal of Physics and Chemistry of Solids 64 (2003) 1579–1583
www.elsevier.com/locate/jpcs
Self-organization processes in impurity subsystem
of solid solutions
E.I. Rogacheva*
Department of Physics, Kharkov Polytechnic Institute, National Technical University,
21 Frunze St, Kharkov 61002, Ukraine
Abstract
New experimental results proving the existence of critical phenomena in the range of small impurity concentrations
(,1.0 at.%) in a number of ternary solid solutions based on IV– VI semiconducting compounds are presented. An anomalous
decrease in X-ray diffraction linewidth and an increase in the lattice thermal conductivity and heat capacity in this concentration
range were observed. The experimental results are analyzed on the basis of percolation theory and fluctuation theory of the
second order phase transitions. From the experimental data, the critical exponents for the lattice thermal conductivity and lattice
heat capacity are determined. It is suggested that self-organization processes (a short-range or long-range ordering of impurity
atoms) accompany the percolation phenomena. The results obtained in this work represent another evidence to the proposition
about the universal character of critical phenomena accompanying the transition from an impurity discontinuum to an impurity
continuum.
q 2003 Elsevier Ltd. All rights reserved.
Keywords: A. Semiconductors; A. Alloys; C. X-ray diffraction; D. Critical phenomena; D. Thermal conductivity
1. Introduction nature of impurity potential, for any type of the interaction
between dopants (deformational, electrostatic, dipole –
Solid solutions represent a broad class of substances, the dipole, etc) one can designate the radius of impurity atom
most widespread and having a great potential for practical ‘action sphere’, within which the crystal properties differ
applications. In the framework of generally accepted notions considerably from those of the matrix, as R0 : In accordance
of the physico-chemical analysis, the physical properties in with one of the problems of percolation theory, viz.
the solid solution region change in a monotonic way, and the ‘problem of spheres’ [9,10], there is a critical concentration
appearance of concentration anomalies of properties (percolation threshold xc ) at which the channels penetrating
indicates the intersection of phase region boundaries. the whole system appear and an infinite cluster consisting of
However, for a number of semiconductor solid solutions overlapping spheres of radius R0 is formed. The effective
we observed [1 – 8] concentration anomalies of different value of xc depends on the range of interactions in the
properties (microhardness H; charge carrier mobility m; system, i.e. on R0 : The formation of the infinite cluster is
lattice thermal conductivity lp ; etc.) in the range of small accompanied by critical phenomena, which must manifest
impurity concentrations (, 1.0 at.%), which indicated the themselves in the case of the solid solutions through
presence of concentration phase transitions (PTs). We anomalies in the concentration dependences of different
suggested [1] that these PTs have the universal character, properties. When the percolation threshold is reached, there
corresponding to the transition from an impurity disconti- appear channels, along which internal elastic stresses caused
nuum to an impurity continuum, and take place according to by the impurity atoms are partially compensated due to the
a percolation scenario [9,10]. Assuming that the properties overlapping of impurity deformational spheres. As a result,
are isotropic and taking into consideration a short-range the movement of dislocations and propagation of elemen-
tary excitations are facilitated. An increase in the dislocation
* Tel.: þ380-572-400-092; fax: þ380-572-400-601. mobility, a decrease in the effective phonon and electron
E-mail address: rogacheva@kpi.kharkov.ua (E.I. Rogacheva). cross-section under the formation of percolation channels
0022-3697/03/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0022-3697(03)00245-2
2. 1580 E.I. Rogacheva / Journal of Physics and Chemistry of Solids 64 (2003) 1579–1583
lead to a drop in H [1,7,8], a growth in lp [6] and m [1,3– 5]
which we observed in the critical region.
To prove the suggestion about the universal character of
the concentration anomalies of physical properties in solid
solutions, it is necessary to expand the scope of objects and
properties to be studied, to perform a more detailed analysis
of experimental data, and to further develop theoretical
grounds. In this work, the new experimental results on the
concentration dependences of the X-ray diffraction (XRD)
linewidth B; lattice thermal conductivity lp ; and specific
heat C in the range of small impurity concentrations in
ternary solid solutions based on IV– VI (SnTe, PbTe, and
GeTe) semiconductor compounds [11], are presented. The
new results are considered jointly with the previously
obtained data and discussed within the framework of the
above mentioned ideas we have been developing in our
studies.
2. Results and discussion
The experimental details of the sample preparation,
XRD study, measurements of the thermal conductivity and
the heat capacity were described earlier in Refs. [2 – 8].
In Fig. 1, the room-temperature dependences of B on the
impurity content in PbTe– CdTe and PbTe –Bi2Te3 solid
solutions based on PbTe are presented. For comparison, we
also show previously obtained data for the PbTe –GeTe [2],
SnTe– Te [12] and CuInSe2 – CdS [13] systems. In deficit
solid solutions (SnTe – Te [12]), the increase in the Te Fig. 1. The dependence of a relative change in the XRD linewidth
content within the SnTe homogeneity region (50.15 – DB=B on the dopant concentration in solid solutions PbTe–CdTe
50.8 at.% Te) corresponds to the increase in the concen- (a),(b), CuInSe2 –CdS [13] (c), SnTe–Te [12] (d), PbTe–GeTe [2]
tration of cation vacancies (, 0.5– 3.2%) caused by the (e), and PbTe–Bi2Te3 (f). a: (400) diffraction line; b: (800)
deviation from stoichiometry and playing the role similar to diffraction line.
the role of impurity atoms. It is seen that in all studied solid
solutions in a relatively narrow range of concentrations of a
second component (, 0.5 – 2.0 mol%), an anomalous homogeneity region relative to the stoichiometric compo-
decrease in B is observed. sition [12].
It is known that among the main factors that cause a A subsequent sharp decrease in B shows that internal
broadening of XRD lines, apart from instrumental factors stresses in the crystal decrease. This is in good agreement
related to the experimental conditions, are (1) the micros- with a drop in H in the vicinity of the critical composition,
tresses in crystal and (2) a small size of coherent scattering which was observed in all studied systems [15] and was
regions [14]. In homogeneous disordered solid solutions attributed to the decrease in internal stresses level with the
with a sufficiently large grain size, the main reason of a reaching of the percolation threshold and the formation of
broadening of XRD lines is microstresses caused by a percolation channels.
difference in sizes of impurity and host atoms. Since all Impurity atoms are centers of local distortions in the
studied solid solutions were prepared and investigated under crystal lattice, sources of internal stresses and strains
the same conditions, the effect of all variables except decreasing in an inverse proportion to the cube of the
microstresses could be ruled out. That is why the broadening distance [16]. Since noticeable displacements of atoms are
of XRD lines we observed after the introduction of the first created within one or two interatomic distances from an
portions of the impurity (Fig. 1) is easy to explain. In the impurity atom, one can consider elastic fields as short-range.
SnTe– Te system (Fig. 1(d)), we do not observe the initial At small impurity concentrations, when distances between
increase in B because alloys with concentrations of cation impurity atoms are much larger than R0 ; elastic fields created
vacancies smaller than , 0.5% do not exist in the by separate atoms practically do not overlap. As the impurity
equilibrium state due to a significant shift of the SnTe concentration increases, elastic fields of neighboring atoms
3. E.I. Rogacheva / Journal of Physics and Chemistry of Solids 64 (2003) 1579–1583 1581
begin to overlap, which leads to a partial compensation of
elastic stresses of opposite signs. After percolation channels
via deformational fields of separate atoms are formed, the
interaction of impurities becomes cooperative. As the
impurity concentration increases, the overlapping of defor-
mational spheres and the compensation of microstresses
gradually spread over the entire crystal (the density of
‘infinite cluster’ grows [9,10]), leading to a decrease in the
overall level of elastic strains in the crystal lattice, which, in
turn, results in a decrease in B: Further introduction of
impurity atoms into this new medium (‘impurity liquid’)
causes new distortions of the crystal lattice and, consequently
a broadening of XRD lines.
Fig. 2. The lattice thermal conductivity lp vs. the dopant
The formation of continuous chains of impurity concentration in the SnTe– InTe (a) and PbTe–GeTe (b) solid
deformational spheres upon reaching the percolation solutions. a: T ¼ 300 K; b: T ¼ 170 K:
threshold must stimulate redistribution of impurity atoms
in the crystal lattice leading to the realization of their
configuration with a minimum thermodynamic potential. As is seen, in the PbTe– Bi2Te3 system (Fig. 2(f)), also at
Elastic interactions between impurity atoms, similarly to least two anomalous regions are observed—in the vicinity of
Coulomb interactions, can lead to the formation of 1 mol% Bi2Te3 and near 3 mol% Bi2Te3. Under the doping
configurations of impurity atoms, which correspond to of PbTe with Bi2Te3, Bi atoms and vacancies are introduced
minima of the elastic energy. Possible self-organization into the cation sublattice simultaneously. The Coulomb
processes may include a long-range ordering of impurity attraction between charged defects of opposite signs (Bi3þ
atoms (‘crystallization of impurity liquid’), a formation of and V22) stimulates processes of chemical interaction
Pb
complexes (short-range ordering), a change in the localiz- leading to the formation of neutral molecular complexes
ation of impurity atoms in the crystal lattice, etc. Under such as Bi2Te3. Thus, in addition to separate impurity atoms,
isovalent isomorphic substitution a long-range ordering is new structural elements appear, and the formation of
more likely. Under heterovalent substitution when the percolation channels through these elements becomes
structure of a matrix differs from the structure of a dopant, possible. On the basis of the above considerations one can
the probability of a short-range ordering in solid solutions suggest that the first anomaly in the B dependence on the
increases. The introduction of a dopant in the form of a impurity content is connected with the formation of
stable chemical compound stimulates the formation of percolation channels linking Bi atoms, while the second
neutral chemical complexes corresponding to the compo- anomaly is related to the formation of percolation channels
sition of this compound. When a certain concentration of through Bi2Te3 complexes. This suggestion is supported by
chemical complexes is reached, the formation of percolation the fact that it is after 3 mol% Bi2Te3 that the charge carrier
channels linking complexes and accompanied by a decrease concentration in the PbTe– Bi2Te3 system does not change
in internal stresses becomes possible. any more [17].
The very convincing argument in favor of self- In Fig. 2, the concentration dependences of the lattice
organization and ordering, which take place upon reaching thermal conductivity lp in SnTe –InTe and PbTe– GeTe
the critical concentration of an impurity, is a dramatic solid solutions are presented. As is seen, in these systems an
decrease in B; in some cases down to the value observed in anomalous increase in lp takes place in the range of small
an impurity-free host-material (the PbTe – Bi2Te3 and impurity contents. In the PbTe – GeTe system, two anom-
PbTe– CdTe systems). alous regions, whose locations correspond to those of
When the solid solution region is sufficiently wide, anomalies in the B dependences on the impurity content, are
different variants of ordering can be realized with observed. We have registered an anomalous increase in lp
increasing impurity concentration. To all appearances, in the range of small impurity concentration earlier in the
two extrema observed in the concentration dependence of PbTe– MnTe system [6] and attributed it to a decrease in the
B in the isovalent PbTe– GeTe system (Fig. 1(e)), can be effective phonon cross-section as a result of the formation of
attributed to the realization of different types of ordering percolation channels near the percolation threshold and a
[2]. A simple calculation shows that a composition of decrease in an overall level of elastic stresses in the crystal
1 mol% GeTe is optimal for an ordered distribution of lattice. The increase in lp up to the values of a host-
impurity atoms over the sites of a simple cubic lattice compound, which was observed in the PbTe – MnTe system
with a ¼ 3 a0 ; whereas at , 1.6 mol% GeTe, a super- [6] is another argument in favor of the suggestion about the
structure of impurity atoms with a fcc lattice and unit cell self-organization processes in impurity subsystem of crystal.
parameter of a ¼ 4 a0 (where a0 is the unit cell parameter In accordance with the modern views [9,10,18], there is an
of the studied alloy) can be formed. analogy between percolation phenomena and the second-order
4. 1582 E.I. Rogacheva / Journal of Physics and Chemistry of Solids 64 (2003) 1579–1583
PTs. In both cases, in the vicinity of a transition, the a dynamic scaling hypothesis for a second order PT, is
properties of a system are determined by strongly developed, equal to w ¼ 0:33; which is in perfect agreement with the
interacting fluctuations, peculiarities of thermodynamic experimental data [18]. This value is rather close to the
quantities obey a power law, and their exponents are called critical exponents of lp we obtained for the PbTe– MnTe
critical exponents. Both percolation and second-order PTs and SnTe– InTe systems, which represents another evidence
manifest themselves through critical phenomena, and are for a close analogy between second order PTs and
characterized by the universality of critical exponents and percolation phenomena.
scaling laws.
The heat capacity C is a universal property showing
anomalous behavior ðC , lT 2 TC l2a Þ in the vicinity of any 3. Conclusion
temperature second-order PT [18]. It can be suggested that a
percolation transition in solid solutions will also be New experimental data, which confirm our earlier
accompanied by an anomaly in C ðC , lx 2 xc l2a Þ: In suggestion about the universal character of critical phenom-
Ref. [19], for the first time anomalous growth in C in PbTe– ena accompanying the transition from ‘an impurity vapor’ to
MnTe solid solutions in the range of small impurity ‘an impurity condensate’, were obtained for IV –VI-based
concentration (1 – 1.25 mol% MnTe) was detected. solid solutions. The analysis of these data and the data
From the experimental concentration dependences of C obtained in our earlier works shows that a narrowing of
in the PbTe– MnTe system [19], plotting the Cðlx 2 xc lÞ XRD lines in the critical region occurs in all studied solid
dependences in a double-logarithmic scale, we determined solutions including the case when the crystal is ‘doped’ with
the critical exponent for the specific heat as a ¼ 0:12 ^ vacancies (the SnTe– Te system [12]). The existence of the
0:02: This value is rather close to the value of a known from range of anomalous growth in the lattice thermal conduc-
the theory of the second-order PTs and confirmed tivity and heat capacity in this critical region is confirmed.
experimentally [18]. It is suggested that the formation of percolation channels
In the PbTe– GeTe system, we detected an anomaly in through impurity centers upon reaching the percolation
the specific heat similar to the one observed in the PbTe– threshold stimulates self-organization processes (long- and
MnTe system [19] (Fig. 3(b), curve 2). The pronounced short-range ordering) in the impurity subsystem. The
peak in the isotherms of C proves the existence of critical narrowing of the XRD line width and the increase in
phenomena. As far as the PbTe– GeTe system is concerned, the lattice thermal conductivity up to the values observed in
the accurate determination of the critical exponent is the impurity-free host compound, which were registered in a
complicated, since at least two anomalies are observed in number of systems, represent a convincing evidence for
the concentration dependences of B and lp : ordering.
An estimate of the critical exponent for the lattice On the basis of our experimental data, the estimates of
thermal conductivity using the experimental data for the the specific heat and the lattice thermal conductivity critical
PbTe- MnTe system [6] and for the SnTe– InTe system exponents are made in the approximation of percolation
(present work), which was made assuming lp , lx 2 xc l2w ; theory and fluctuation theory of the second order PTs.
yielded w ¼ 0:25 ^ 0:05: It is known [18] that the
theoretical value of the lp critical exponent w ðl ,
lT 2 TC l2w Þ; calculated for superfluid Helium 4 using
Acknowledgements
The author thanks Pinegin V.I. and Tavrina T.V. for their
assistance in carrying out the X-ray studies.
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