contribution of vibrational entropy in gibbs free energy

[musanna_galib]

Hello,
Does the entropy term mentioned in the free energy table indicate the sum of contributions of translational, Rotational, and Vibrational degrees of freedom?

Code: Select all

 Free energy of the ion-electron system (eV)
  ---------------------------------------------------
  alpha Z        PSCENC =         1.79219085
  Ewald energy   TEWEN  =       446.99159274
  -Hartree energ DENC   =      -949.08121877
  -exchange      EXHF   =         0.00000000
  -V(xc)+E(xc)   XCENC  =        39.37578861
  PAW double counting   =      1454.99506404    -1425.33624586
  entropy T*S    EENTRO =         0.00301559
  eigenvalues    EBANDS =      -239.48516022
  atomic energy  EATOM  =       607.22751992
  Solvation  Ediel_sol  =         0.00000000
  ---------------------------------------------------
  free energy    TOTEN  =       -63.51745310 eV

  energy without entropy =      -63.52046869  energy(sigma->0) =      -63.51845829

I calculated the vibrational frequency with IBRION = 5 for NSW = 1. Then using the following eqn calculated the vibrational entropy of a harmonic oscillator which gives 0.0057 eV. Therefore I am confused if I am missing anything here.

[henrique_miranda]

No.
The entropy term reported in that table includes only the electronic contribution.
You can verify that is the case because even when you don't calculate the vibrational frequencies you get that value for the entropy.

As a side note:
If you want to compute the vibrational entropy for a crystal you might want to consider computing and interpolating the phonon dispersion using phonopy:
https://phonopy.github.io/phonopy/formu ... es#entropy