This project aims to simulate the density of states and band structure of joined bi-layer graphene using density functional theory (DFT) and compare it to graphene. DFT simulations were performed on joined bi-layer graphene and graphene to calculate potential energy, defect formation energy, and density of states. The bi-layer graphene system was found to be not spin polarized with a low defect formation energy of 0.001 eV per atom. Additionally, the project works to develop a 3D printing process for proposed graphene structures by converting structure files to STL files for printing.
Motional Gaussian states and gates for a levitating particleOndrej Cernotik
Coherent scattering has recently attracted attention as a means of controlling the motion of levitated particles in three dimensions using a single optical cavity. In these systems, scattering of photons from the trapping field to a cavity mode has been used to cool all three modes of the centre-of-mass motion of levitated particles. The possibility of employing coherent scattering for more general quantum control has, however, not yet been discussed in the literature. Here, we present strategies for generating nonclassical correlations and for engineering interactions between motional modes of levitated particles using coherent scattering. We expand the theory developed by Gonzalez-Ballestero et al. to realize more general bilinear interactions in levitated optomechanics with coherent scattering. Going beyond the simple stationary picture, we introduce amplitude modulation as an important tool to modify the optomechanical interaction and discuss how it can be used to resonantly enhanced certain parts of the interaction, allowing, for example, strong one- and two-mode squeezing of motion. Our results thus show the potential of using coherent scattering for full quantum control of the motion of levitated particles.
We build a network of locations from Twitter geolocalized tweets. We then analyze the small-world and scale-free properties of such spatial network. We also use modularity to reveal the structre of neighborhood communities.
Motional Gaussian states and gates for a levitating particleOndrej Cernotik
Coherent scattering has recently attracted attention as a means of controlling the motion of levitated particles in three dimensions using a single optical cavity. In these systems, scattering of photons from the trapping field to a cavity mode has been used to cool all three modes of the centre-of-mass motion of levitated particles. The possibility of employing coherent scattering for more general quantum control has, however, not yet been discussed in the literature. Here, we present strategies for generating nonclassical correlations and for engineering interactions between motional modes of levitated particles using coherent scattering. We expand the theory developed by Gonzalez-Ballestero et al. to realize more general bilinear interactions in levitated optomechanics with coherent scattering. Going beyond the simple stationary picture, we introduce amplitude modulation as an important tool to modify the optomechanical interaction and discuss how it can be used to resonantly enhanced certain parts of the interaction, allowing, for example, strong one- and two-mode squeezing of motion. Our results thus show the potential of using coherent scattering for full quantum control of the motion of levitated particles.
We build a network of locations from Twitter geolocalized tweets. We then analyze the small-world and scale-free properties of such spatial network. We also use modularity to reveal the structre of neighborhood communities.
Consistent metric approximation - Main idea - Sampling conditions - Surface properties - Sufficient conditions for consistency (Bernstein-de Silva-Langford-Tenenbaum theorem) - Why both conditions are important? - Probabilistic version
No Smoking Please - a wearable persuasive computing deviceCharlette Proto
Preliminary design of a wearable persuasive computing device, a presentation for Ambient Visualisation with Devices (DESC9179), semester 2, 2007, Faculty of Architecture Design and Planning, The University of Sydney, by Piotr Kulaga.
http://home.exetel.com.au/dataist/portfolio/nsp/index.htm http://www.youtube.com/watch?v=xkMCtFqumP0&feature=relmfu
Consistent metric approximation - Main idea - Sampling conditions - Surface properties - Sufficient conditions for consistency (Bernstein-de Silva-Langford-Tenenbaum theorem) - Why both conditions are important? - Probabilistic version
No Smoking Please - a wearable persuasive computing deviceCharlette Proto
Preliminary design of a wearable persuasive computing device, a presentation for Ambient Visualisation with Devices (DESC9179), semester 2, 2007, Faculty of Architecture Design and Planning, The University of Sydney, by Piotr Kulaga.
http://home.exetel.com.au/dataist/portfolio/nsp/index.htm http://www.youtube.com/watch?v=xkMCtFqumP0&feature=relmfu
Pentacene-Based Organic Field-Effect Transistors: Analytical Model and Simula...IDES Editor
Organic Field-Effect Transistors, OFETs, attract
much interest recently and their proficiency and hence
applications are being enhanced increasingly. However, only
analytical model of old field-effect transistors, developed for
silicon-based transistors, and their relevant numerical
analyses have been used for such devices, so far. Increasing
precision of such models and numerical methods are essential
now in order to modify OFETs and propose more effective
models and methods. This study pegs at comparing current
analytical model, simulation methods and experiment data
and their fitness with each other. Certainly, four aspects of
results of three abovementioned approaches were examined
comparatively: sub-threshold slope, on-state drain current,
threshold voltage and carrier mobility. We embark to analyze
related experiment data of OFETs made by pentacene, as the
organic material, along with various organic gate insulators
including CyEP, PVP, PMMA, Parylene-C and Polyimide and
then to offer their results, comparatively.
Enhancing the Performance of P3HT/Cdse Solar Cells by Optimal Designing of Ac...IOSRJEEE
The present study examined the influence of different condition like as doping , in active layer, on the performance of P3HT/CdSe Solar cells .In this work, we analyzed the best doping for the configuration of P3HT/ CdSe in order to improve the performance of the solar cell. For this aim, we investigated the current density of electrons, the electric field, the short-circuit current and the open-circuit voltage in different doping . The results indicate that when the doping is increased in P3Ht and is decreased in CdSe, the current density of electrons, the electric field, the short-circuit current, and the open-circuit voltage are increased. Finally, we obtained doping of and for electron and hole donor respectively as the best doping for this configuration
Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of el...Sérgio Sacani
High-energy cosmic-ray electrons and positrons (CREs), which
lose energy quickly during their propagation, provide a probe of
Galactic high-energy processes1–7 and may enable the observation
of phenomena such as dark-matter particle annihilation or
decay8–10. The CRE spectrum has been measured directly up to
approximately 2 teraelectronvolts in previous balloon- or spaceborne
experiments11–16, and indirectly up to approximately 5
teraelectronvolts using ground-based Cherenkov γ-ray telescope
arrays17,18. Evidence for a spectral break in the teraelectronvolt
energy range has been provided by indirect measurements17,18,
although the results were qualified by sizeable systematic
uncertainties. Here we report a direct measurement of CREs in the
energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the
Dark Matter Particle Explorer (DAMPE)19 with unprecedentedly
high energy resolution and low background. The largest part of
the spectrum can be well fitted by a ‘smoothly broken power-law’
model rather than a single power-law model. The direct detection of
a spectral break at about 0.9 teraelectronvolts confirms the evidence
found by previous indirect measurements17,18, clarifies the behaviour
of the CRE spectrum at energies above 1 teraelectronvolt and sheds
light on the physical origin of the sub-teraelectronvolt CREs.
EFFECTIVE PEEC MODELING OF TRANSMISSION LINES STRUCTURES USING A SELECTIVE ME...EEIJ journal
The transmission lines structures are quite common in the system of electromagnetic compatibility (EMC)
analysis. The increasing complexities of physical structures make electromagnetic modeling an
increasingly tough task, and computational efficiency is desirable. In this paper, a novel selective mesh
approach is presented for partial element equivalent circuit (PEEC) modeling where intense coupling parts
are meshed while the remaining parts are eliminated. With the proposed approach, the meshed ground
plane is dependent on the length and height of the above transmission lines. Relevant compact formulae for
determining mesh boundaries are deduced, and a procedure of general mesh generation is also given. A
numerical example is presented, and a validation check is accomplished, showing that the approach leads
to a significant reduction in unknowns and thus computation time and consumed memories, while
preserving the sufficient precision. This approach is especially useful for modeling the electromagnetic
coupling of transmission lines and reference ground, and it may also be beneficial for other equivalent
circuit modeling techniques.
APS D63.00002 Tight Binding Simulation of Finite Temperature Electronic Struc...DavidAbramovitch1
Abstract: D63.00002 : Improved Accuracy Tight Binding Model for Finite Temperature Electronic Structure Dynamics in Methyl Ammonium Lead Iodide (MAPbI3)
Presenter:
David Abramovitch
(Department of Physics, University of California, Berkeley)
Authors:
David Abramovitch
(Department of Physics, University of California, Berkeley)
Liang Tan
(Molecular Foundry, Lawrence Berkeley National Lab)
Halide perovskites are promising photovoltaic and optoelectronic materials. However, computing electronic properties and dynamics at finite temperature is challenging due to nonlinear lattice dynamics and prohibitive computational costs for ab initio methods. Tight binding models decrease computational costs, but current models lack the ability to accurately model instantaneous atom displacement and reduced symmetry at finite temperature. We present a parameterized tight binding model for MAPbI3 capable of predicting instantaneous electronic structures for large systems based on atomic positions extracted from classical molecular dynamics. Our tight binding Hamiltonian predicts instantaneous atomic orbital onsite energies and hopping parameters accurate to 0.1 to 0.01 eV compared to DFT across the orthorhombic, tetragonal, and cubic phases, including effects of temperature, reduced symmetry, and spin orbit coupling. This model allows for efficient calculation of instantaneous and dynamical electronic structure at the length and time scales required to address coupled electronic and ionic dynamics, as required for predicting temperature dependence of carrier mass, band structure, free carrier scattering, and polaron transport and recombination.
Similar to Physics NSF_REU Tim Kilmer Poster 2016 (20)
APS D63.00002 Tight Binding Simulation of Finite Temperature Electronic Struc...
Physics NSF_REU Tim Kilmer Poster 2016
1. Figure 2: Graphene bands and density of
states.
Figure 3: Joined Bi-layer Graphene bands,
and density of states.
Potential Energy Per Atom = 0.878 eV
Defect Formation Energy = 0.001 eV
Figure 4: 3d Prints
2016 Research Experience for Undergraduates:
Physics @ Rensselaer
Simulation and Printing of Joined Bi-Layer Graphene
Timothy W. Kilmer1,2, Humberto Terrores2
1State University of New York (SUNY) Oneonta
2Rensslear Polytechnic Insitute
Project Goals Methods
Introduction
Results and Discussion Conclusions and Impact
Future Directions
Acknowledgments
The purpose of this project is to
simulate the density of states and
bands structure of two layer
graphene connected by a hole
(Figure 1) and compare properties
to Graphene. On the side, to
develop a process to print proposed
structure, Buckminsterfullerene, and
large fullerenes intended to
demonstrate crystal structures.
DFT Simulation
Simulations for Joined Bi-Layer
Graphene and Graphene were
done on CCI BlueGene q/amos and
SDCS Comet both running the
Quantum Espresso (QE) programs.
Each sample was relaxed to the
lowest total energy. Self Consistent
Field (SCF) and band calculations
were done on both structures using
QE pw.x program. Finally the
density of states were calculated
using QE dos.x program.
Printing
The models start as Cartesian
coordinates generated from
Mathematica and is made into a
Protein Data Bank (PDB) file.
These Files are then imported into
Blender using Atomic Blender to
show atoms as spheres and bonds
as cylinders. The file size of the
model was reduced and a
thickness is applied so the model
can be processed. The model was
then exported as a STL and sent to
RPI’s Rapid Prototyping Facility to
be printed.
Future directions to be done involve
simulating lattice vibrations, carrier
density, and electron flow.
Comparisons can also be made to
graphene anti-dots and bi-layer
graphene. The process to of
improving the 3D printing process
to print large complex fullerenes.
Thanks to Humberto Terrones, Aldo , Micheal Lucking,
Larry Ruff, CCI RPI, Comet Exede, SUNY Oneonta,
Quantum Espresso
Project was supported by NSF
References
H. Terrones M Terrones, Journal of Phys. 5, 1 (2003)
W. Kohn and L. J. Sham, Physical Review 140, pp. 1333 (1965)
L.A Chernozatonskii, V.A. Demin, & AA Artyukh, JETP Let. 5, pp 353-359 (2014)
With the use of DFT, the bi-layer
graphene system was not spin
polarized due to no change in the
total energy of the system. Also the
formation energy of the system per
atom was 0.001 eV. However this
could be changed by doping or
changing the geometry of the hole.
Such as, the hole radius and hole
depth.
Figure 1:
Joined bi-layer graphene side view (Left) and top view (Right).
Images generated in Mathematica.
Using density functional theory
(DFT) will give insight on the band
structure, density of states, spin
polarization , and the total energy
per atom of the system. Molecular
structures can be represented as a
file such as xyz, vasp, or PDB,
which will be used to define the
STL mesh for 3D printing and be
used for DFT.
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