[Pw_forum] RE: Free energy w.r.t. T and QHA

[W. YU]

Dear Stefano,

Thank you very much for your explanations. 

Maybe I didn't make myself clear enough!

I understand the general processures of a QHA
calculation, but what really bothers me is that many
DFT code with phonon functionality simply calculates
F-T relationship at a SPECIFIC volume and made a F-T
curve. Of course, there is nothing wrong in doing so
if no real situation is considered since F IS a
function of T and V (or other structural parameters).
But this is in fact incorrect when thermal expansion
is concerned in the spirit of QHA. Then in order to
make a F-T curve, phonon spectrum has to be found at
each equilibrium geometry under the given T instead of
the single set of spectra.

Hope I have made it clearer this time! Thanks

W. YU





 
____________________________________________________________________________________
Get your own web address.  
Have a HUGE year through Yahoo! Small Business.
http://smallbusiness.yahoo.com/domains/?p=BESTDEAL