Temperature

This page gives hints on how to compute vibrational free energy, entropy, specific heat, thermal expansion, as well as atomic temperature factors with the ABINIT package.

Introduction

When the phonon band structure and corresponding eigenvectors are known over the whole Brillouin Zone, thanks fo Fourier interpolation (see topic_PhononBands), integrals can be performed, allowing to obtain a wealth of properties, like free energy, entropy, specific heat, as well as atomic temperature factors. For applications of this technique, see [Lee1995].

Moreover, knowing such information for different volumes allows one to compute the thermal expansion, see gruns_ddbs.

The input variables needed to perform the interpolation over the Brillouin Zone are described in topic_PhononBands and are not listed again in the present topic.

Related Input Variables

compulsory:

• thmflag THerMal FLAG

basic:

• gruns_nddbs GRUNeiSen Number of DDB files
• ntemper Number of TEMPERatures
• temperinc TEMPERature INCrease
• tempermin TEMPERature MINimum

useful:

• gruns_ddbs GRUNeiSen DDBS
• prtvol PRinT VOLume
• thmtol THerModynamic TOLerance

Selected Input Files

v2:

• tests/v2/Input/t15.abi
• tests/v2/Input/t16.abi

Tutorials

• The tutorial Response-Function 2 (RF2) presents the analysis of the DDBs that have been introduced in the preceeding tutorial RF1. The computation of the interatomic forces and the computation of thermodynamical properties is an outcome of this tutorial.