Dear Nicolas If you use the smearing=FD the degauss parameter is the electronic temperature (T) that gives you a measure of the (physical) broadening of the Fermi distribution function (the deviation from its 0 K step shape). if you use other smearing schemes degauss still measures the smearing width of your (generalized) distribution function but does not correspond exactly to the physical temperature anymore. Generalized distribution functions (instead of FD) are used for numerical convenience (i.e. to reduce the dependence of the total energy on the smearing, particularly useful if you want to recover the physics at 0 K). Useful reference: DOI:10.1103/PhysRevB.51.6773 See also refs 16 and 17 quoted therein.
regards, Matteo On Wed, Mar 27, 2013 at 3:18 AM, Nicolas FERNANDEZ <nicolas.fernandez at etu.univ-provence.fr> wrote: > Dear all, > > I try to evaluate the electronic entropy contribution to the vacancy > formation. > > I used smearing with Fermi-Dirac function and a degauss value of 0.01 Ry > > A line in the output file look very promising to calculate entropy : > smearing contrib. (-TS) = -0.11576742 Ry > but I have a doubt about the "T" term. > It (probably) corresponds to the temperature but the temperature of what? > What is the temperature unit? > How to calculate or set it? > Is my approach correct to evaluate the electronic entropy? > > Thank you for your responses. > > Best regards, > > Nicolas > PhD student > Aix-Marseille University > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- Matteo Cococcioni Department of Chemical Engineering and Materials Science, University of Minnesota 421 Washington Av. SE Minneapolis, MN 55455 Tel. +1 612 624 9056 Fax +1 612 626 7246
