The ABINIT Users Mailing List ( CLOSED )

[Nicola Marzari <marzari@MIT.EDU>]

Nicola Marzari wrote:
> Care needs to be paid, though - when you add a fictitious temperature,
> the variational functional that is minimized becomes the
> free energy E-TS ; S will be different from zero, and finite, for
> fractional occupations, but you only want to get the E term from
> abinit (I am not familiar with the output, so I can't advise on
> how to remove -TS).

Sorry, let me be more precise here - when you deal with an atom
or a molecule, you only want E, since -TS doesn't really mean
anything.

If you deal with a solid (i.e. a metal) you should really use
E-TS, because that is the variational functional you minimized.
If anything, you should use a fictitious entropy (such as
that given by "cold smearing" or "Methfessel-Paxton" ioccopt)
that minimizes the effects of temperature. The bibliography
section of the abinit web sites contains a few citations to the
relevant literature.

                        nicola

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