[Pw_forum] a question about calculating free energy

[Chaohao Hu]

Dear PWscf users,
I did some phonon calculations using pw.x and ph.x and obtained the results of phonon density of states (1.phdos). But when I calculated the free energy using fqha.x, some wrong informations always appear.
In the fqha.f90 file, I deleted the following line "if (abs(nu(i)-de*(i-0.5d0)).gt.1.0d-6) stop ' wrong grid'" (I think that the limitative condition is too rigorous).

the executing processing:
fqha
 file containing the dos >>>1.phdos
1368
0.2048
1.0
 file for the Free energy >>>1.txt
 temperature >>>500.0

the error information:
"run-time error M6202: MATH
- log: SING error"

I also know the negative value appears in log function described as the following line,
"    if (T.gt.0.d0) Ftot=Ftot+dos(i)*a2*T*log(1.0d0-exp(-a3*nu(i)/T))
"
but I do not know how to resolve this problem.
Who can help me?
Thanks in advance.

Best regards,
Chaohao
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