TY - THES

T1 - Assessment of Various DFT-based Methods for Predicting Temperature Dependence of Elastic Constants

AU - Jechtl, Tobias

N1 - no embargo

PY - 2021

Y1 - 2021

N2 - The major concern of this thesis is to outline several methodological approaches to compute the temperature dependence of elastic constants of cubic monocrystalline metallic materials from an atomistic point of view and assess them among each other. In particular, the DFT-based VASP software toolkit in combination with the VSC and the HPC cluster of the Montanuniversität Leoben are utilised to perform these CPU-intensive calculations. It is shown that ground-state elastic constants can be depicted as functions of volume and thus are dependent on the distance of neighbouring atoms. Furthermore, the quasiharmonic Debye model and a phonon-based QHA approach within the phonopy software package are employed to predict selected thermal material properties, e.g. the thermal expansion, whereas the latter method is considered to provide more realistic results. Eventually, the elastic constants are constituted as functions of temperature-dependent volume, whereby the outcomes associated with the phonon-based approach are in good accordance with experimental data.

AB - The major concern of this thesis is to outline several methodological approaches to compute the temperature dependence of elastic constants of cubic monocrystalline metallic materials from an atomistic point of view and assess them among each other. In particular, the DFT-based VASP software toolkit in combination with the VSC and the HPC cluster of the Montanuniversität Leoben are utilised to perform these CPU-intensive calculations. It is shown that ground-state elastic constants can be depicted as functions of volume and thus are dependent on the distance of neighbouring atoms. Furthermore, the quasiharmonic Debye model and a phonon-based QHA approach within the phonopy software package are employed to predict selected thermal material properties, e.g. the thermal expansion, whereas the latter method is considered to provide more realistic results. Eventually, the elastic constants are constituted as functions of temperature-dependent volume, whereby the outcomes associated with the phonon-based approach are in good accordance with experimental data.

KW - Dichtefunktionaltheorie

KW - computerunterstützte Materialwissenschaft

KW - elastische Konstanten

KW - Elastizitätstensor

KW - Temperaturabhängigkeit

KW - quasiharmonische Approximation

KW - quasiharmonisches Debye Modell

KW - VASP

KW - phonopy

KW - Phononenberechnungen

KW - temperaturabhängige Materialeigenschaften

KW - Aluminium

KW - Density Functional Theory

KW - DFT

KW - elastic constants

KW - temperature dependence

KW - stress-strain method

KW - energy-strain method

KW - Vienna ab-initio simulation package

KW - VASP

KW - quasiharmonic Debye model

KW - quasiharmonic approximation

KW - phonopy

KW - aluminum

KW - isothermal bulk modulus

KW - thermal expansion coefficient

KW - heat capacity at constant pressure

KW - elasticity tensor

KW - adiabatic elastic constants

M3 - Master's Thesis

ER -