[Pw_forum] Re: Re: [Pw_forum] a question about calculating free energy

[Chaohao Hu]

Hi,thank you for your great help. In my pdos file, the first frequence value is indeed negative. When deleting the first line, it can run very well.

Best regards,
Chaohao

> Hi,
> 
> > 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.
>   
> If you have imaginary (negative in your files)
> frequences, your system is dynamically unstable, so, 
> it is meaningless to calculate the free energy for
> such a kind unstable system. 
> 
> Bests,
> Eyvaz.
> 
> 
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