Dear all Reference is made to the output of the executable F_QHA.x;
AA. The output of F_QHA.x starts with a header like the following QUOTE # Zero vibration energy: 0.0036240239 (Ry/cell) # Phonon DOS norm : 6.036119 ! 3N for check purpose, N number of atoms in the unit cell # T in K, F_vib in Ry/cell, C_v in R (the universal gas constant by 3N modes), S in k_B # # T E_internal F_vibration Specific heat (C_v) Entropy UNQUOTE For test purposes, I run F_QHA.x for the cases of alpha- and beta- Tin. I can see that "F_vibration vs T" graphs cross above 300 K (in cosnsistency with the phase transition). This does not hold for the sum E_internal+F_vibration (which I assumed to be the Heelmholtz free energy in the first place). So, is it safe to conclude that F_vibration is actually the Helmholtz free energy? And if so, what does E_internal stand for? BB. As a prerequisite to QHA, the PHDOS.out is obtained. What does it mean when one gets negative frequencies in tjis file? Is it a matter of poor k-point sampling or an indication of unstable structue at a given Temperature? Is it fair to errase the negative parts and proceed withy QHA for the thermodynamical properties? Thank you very much, -- Eleftheria Gkogkosi Applied Mathematics & Physics Dept. National Technical University of Athens http://users.ntua.gr/elefthe _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
