EFFECT OF STRAIN RATE AND TEMPERATURE ON MECHANICAL PROPERTIES OF SILICON NANOWIRE: A MOLECULAR DYNAMIC SIMULATIONS STUDY

1. EFFECT OF STRAIN RATE AND
TEMPERATURE ON MECHANICAL
PROPERTIES OF SILICON NANOWIRE:
A MOLECULAR DYNAMIC SIMULATIONS
STUDY
Guided by - Dr. Soumya Saswati Sarangi
Presented by – Chandan Bhramarjal
Redg. No - 2007140016

2. 01
Outline
Introduction
Page 1
02 Objective
03 Methodology
04 Result
05 Conclusion
06 References
07 Acknowledgement

3. Introductions
Nanowires
• Nanowires are microscopic wires that have a diameter measured in
nano-meter scale i.e., 10-9 meters. Nanowires exhibit unique
mechanical, electrical, magnetic, optical, thermoelectric, and
chemical properties. For such reasons numerous investigation and
extensive studies have been undertaken to gain further insights on the
properties of nanowire.
• The scope of applications in a broad area have been expected from
their distinct characteristics, such as the building blocks of nano-
electromechanical systems (NEMS), solar energy conversion devices,
thermo-electronics and sensor devices etc.
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Gold nanowires
Silver nanowires

4. Semiconductor Nanowires
• Metals and semiconductor nanowires are one of the most exciting
nanomaterials and have attracted intensive research due to their
unique mechanical, thermal, magnetic and electrical properties.
• Silicon nanowires (SiNWs) are considered as most popular among
semiconductor nanomaterials due to their remarkable electrical and
mechanical properties.
• Silicon nanowires are most likely to be utilised in future field-effect
transistors and advanced sensors.
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Silicon nanowires

5. Objective of this work
The layout of the objectives are as follows:
• Study and compare Young’s modulus of three potentials for bulk silicon
• Study the effect of strain rate variation on mechanical characteristics for silicon
nanowire
• Study the effect of temperature variation on mechanical characteristics for silicon
nanowire
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6. Methodology
• Molecular dynamics (MD) is a standard simulation technique for predicting materials structures and
behaviour at the atomic scale. MD simulations are a computational method of simulating the
movement of each individual atom or molecule in a large system containing hundreds of thousands to
several millions of atoms or molecules.
• MD simulation is based on the Newton’s second law which is used to determine the motion of each
atom:
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𝑚𝛼𝑎𝛼 = 𝑓
𝛼
Here atom 𝜶 has the mass mα, the acceleration is 𝒂𝜶, and the force acting on atom 𝛼 is 𝒇𝜶. The
interaction potential V is given by force 𝑓𝛼, this is specified for the system:
𝑓
𝛼 = −𝛻𝛼 𝑉 𝑟

7. Methodology
The framework of a standard MD simulation is depicted in this flow chart.
Page 6

8. Methodology
• We utilise the LAMMPS software to run the MD simulation. The name "LAMMPS" is an acronym for
"Large-scale Atomic/Molecular Massively Parallel Simulator." It's an open-source programme created by
Sandia National Laboratories for molecular dynamics simulations, with a focus on material modelling.
• Visualization of the atoms is carried out using the OVITO package.
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9. Results
Interatomic potential function plays a significant role in the MD simulation and selection of it is very crucial.
In this section we will compare the three inter-atomic potentials to see how they predict the mechanical
properties and fracture behaviour of bulk silicon.
The three interatomic potentials observed are:
• the Stillinger Weber
• the Tersoff
• The MEAM potential
Page 8

10. Page 9
The stress vs strain curve for bulk silicon
structure
The stress vs strain curve can be used to calculate the
mechanical characteristics of materials.
• Elastic deformation region
• Yield point
• Fracture point
The calculated Young's Modulus of MEAM potential is 129.6
GPa, which is quite close to the experimentally measured
value of 130 Gpa [1] for bulk Silicon.
For this reason, we've decided to carryout further
simulations using MEAM potential.
Comparison of interatomic potentials for bulk silicon

11. Page 10
The above picture shows deformation of the bulk silicon cube using MEAM potential at temperature 300K and
strain rate 0.005 ps-1. (a) Strain is 0, initial state; (b) Strain is 0.18, tensile state; (c) Strain is 0.28, fracture occurs.
(a) (b) (c)

12. Page 11
Results for silicon nanowire
Here’s the top and side view of the silicon
nanowire we are going to be using which
has a length of 10nm and diameter 3nm.
Side view
Top view

13. Page 12
• the first stage in stress-strain curves is linear indicates
that elastic deformation.
• the stress-strain curves in this linear stage are almost
overlapped. That means Young’s modulus is
independent of strain rate.
• Beyond elastic stage, the stress drops abruptly
indicating influence of strain rates after elastic stage.
• Higher the strain rate indicate the higher the fracture
strain and yield stress.
The stress vs strain curve for silicon nanowire at different
strain rates.
Results for silicon nanowire
Effect of strain rates

14. Page 13
Higher the strain rate indicates higher fracture strain and yield stress.

15. Page 14
Kinetic energy determines systems momentum and thermal
excitation but potential energy assists in investigation of
mechanical characteristics.
• The potential energy curve rises linearly with increase in
strain and reaches to an elastic limit.
• The decreasing ratio of the first drop is a result of bond
energy being released by breaking bonds indicates that the
regular crystal structure of NW is being disrupted.
The potential energy vs strain curve for silicon
nanowire at different temperature.
Effect of temperature

16. Page 15
Pictures of silicon nanowires at 300K
temperature and 0.005 ps-1 strain rate.
• (A) Initial stage at strain 0
• (B) Tensile stage at strain 0.155
• (C) Fracture state at strain 0.187
(A) (B) (C)
Effect of temperature

17. Page 16
Temperature has significant impact on nanowire deformation
behaviour.
• As the increase in temperature occurs, deformation of
nanowire is accelerated.
• Temperature causes dislocations, hence higher temperature
causes nanowire to reach the yield stress point prematurely.
The stress vs strain curve for silicon nanowire at
different temperatures.
Effect of temperature

18. Page 17
The higher temperature the lower the Youngs mod, yield strength, yield strain and fracture strain.

19. Conclusion and future scope
• It is observed from our results that the yield strength, yield strain and fracture strain increased with increase in strain
rate, whereas the Young’s modulus remain unaffected.
• Temperature has an equally important influence on the mechanical characteristics of the SiNW as it affected both the
elastic and plastic characteristics profoundly.
• With increase in temperature, the Young's modulus, yield strength, yield strain and fracture stain of the NW are found
to decrease.
• These results show that the with increase in strain rate and decrease in temperature, the strength of the SiNW
increases.
• Other factors that influence the mechanical properties of NWs include size, and orientation.
• The present study can be helpful for further extended research works in the field of silicon nanomaterials and its
related areas.
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20. References
1. M. A. Hopcroft, W. D. Nix, and T. W. Kenny, (2010) “What is the Young’s Modulus of Silicon?,” J.
MICROELECTROMECHANICAL Syst., vol. 19, no. 2, p. 229.
2. A. I. Hochbaum and P. Yang, (2010) “Semiconductor nanowires for energy conversion,” Chem. Rev., vol. 110, no.
1, pp. 527–546.
3. [2] K. Davami, J. S. Lee, and M. Meyyappan, (2011) “Nanowires in thermoelectric devices,” Trans. Electr.
Electron. Mater., vol. 12, no. 6, pp. 227–233.
4. S. Barik and S. S. Sarangi, (2022) “Effect of temperature on mechanical properties of zirconium nanowire using
MD simulations,” Mater. Today Proc., vol. 56, pp. 60–65.
5. E. B. Tadmor and R. E. Miller, (2011) “Modeling materials : continuum, atomistic, and multiscale techniques,” p.
759.
6. K. Kang and W. Cai, (2010) “Size and temperature effects on the fracture mechanisms of silicon nanowires:
Molecular dynamics simulations,” Int. J. Plast., vol. 26, no. 9, pp. 1387–1401.
7. A. Furmanchuk, O. Isayev, T. C. Dinadayalane, D. Leszczynska, and J. Leszczynski, (2012) “Mechanical properties
of silicon nanowires,” Wiley Interdiscip. Rev. Comput. Mol. Sci., vol. 2, no. 6, pp. 817–828.
8. B. J. Lee, (2007) “A modified embedded atom method interatomic potential for silicon,” Calphad Comput.
Coupling Phase Diagrams Thermochem., vol. 31, no. 1, pp. 95–104.
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21. Acknowledgement
I owe this unique opportunity to place on record my deep sense of gratitude and indebtedness to Dr. Soumya
Saswati Sarangi, Physics Department, VSSUT, Burla for her scholastic guidance, prudent suggestions.
I heartily owe my sincere gratitude and thankfulness to Prof. Ganeshwar Nath, HOD of department of physics for
providing all type of facilities to complete my project.
I express my profound gratitude to Mr Sheshadev Barik, Research scholar, Department of Physics, VSSUT, Burla for
his ceaseless encouragement, valuable suggestions and constant help for this work.
I am sincerely grateful to Prof. Bansidhar Majhi, Vice Chancellor, VSSUT, Burla for providing the necessary facilities
to carry out the project work.
I would also like to extend my thanks to all the faculties, office staffs and research scholar of the physics
department and my friends of physics Department of VSSUT, Burla. Above all, I am grateful to my family members
for the tremendous amount of inspiration and moral support.
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22. Thank You