I want to incorporate the temperature effect on elastic constant (EC) of a system using VASP. Standard DFT calculation with IBRION = 5 or 6 with ISIF = 3 tags can generate elastic constant at 0 Kelvin for a particular volume. But I am a bit confused when temperature is coming into picture.
Can somebody please explain a detailed way for getting the temperature effect by considering both theories and code (VASP)?
Dear Niraja,
I think, not DFT software incorporate the temperature dependence.
So, it is better to solve the Differential Equation by Finite Difference method with some intuitive dependence on Elastic property variation and then find the variation.
If you can use the first principle Analysis, then the variation function will be more physical.
Best Wishes
N Das
Temperature effects can be divided into thermal expansion and electron phonon coupling. Quasi Harmonic Approximation gives you POSCARs at different temperatures based on phonon calculations of strained systems. Monte Carlo sampling based on phonon vibrational modes gives you lots of POSCARs at a given temperature, and you need to do thermal average (convergence of supercell size and number of Monte Carlo sampling points can be important). For reference, check our PRB paper and Supplementary Materials:
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.100.161101
for code, VASP 6 has MC implemented.
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