DFT calculations assume zero temperature and a perfect crystal, Silicon is an insulator under these conditions
Lorenzo Paulatto - Paris On 10 May 2015 09:16, "reza vatan" <[email protected]> wrote: > Dear Lorenzo, > > Thanks for replying. The single SCF step does not converge. > Any way by changing "occupations=smearing" to "occupations=fixed", I could > fix the convergence problem for both SCF cycle and relaxation, although I > don't know if this occupation mode is appropriate choice for semiconductor > or not. > > Please let me know if you know what is the best choice for occupation mode > in the case of a semiconductor like Silicon. > > Best, > Reza > > On Tue, May 5, 2015 at 2:09 AM, Lorenzo Paulatto < > [email protected]> wrote: > >> Dear Reza, >> what does not converge? The single SCF step or the relax calculation? >> >> Please not that you are not doing a relax calculation but a damped >> dynamic one. If your damped dynamics are not damped enough it will never >> converge. >> >> Use ion_dynamics="bfgs" instead (which is the default, do not play with >> parameters if the default ones work) >> >> regards! >> >> I also notice that you are using a smearing to integrate the Fermi >> surface of Silicon, but Silicon is not a metal. If fore some mysterious >> reason you want to use a smearing you may need more k-point, but the >> calculation SCF should converge regardless. >> >> >> On 04/05/15 23:42, reza vatan wrote: >> > Dear users, >> > >> > I have been trying to perform "calculation=relax" on Si bulk structure >> > generated by a super cell ( or unit cell) containing 8 atom repeating in >> > a simple cubic lattice (ibrav=1). I created this super cell, by cutting >> > a cell containing 8 atoms from perfect Si bulk structure obtained from >> > experimental and theoretical results. The problem is that my calculation >> > doesn't converge at all, although the structure seems to be relaxed. Is >> > there any one here knows where the problem is. I attached the input file >> > that I run. >> > >> > Best, >> > Reza >> > >> > >> > _______________________________________________ >> > Pw_forum mailing list >> > [email protected] >> > http://pwscf.org/mailman/listinfo/pw_forum >> > >> >> -- >> Dr. Lorenzo Paulatto >> IdR @ IMPMC -- CNRS & Université Paris 6 >> phone: +33 (0)1 44275 084 / skype: paulatz >> www: http://www-int.impmc.upmc.fr/~paulatto/ >> mail: 23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cx 05 >> _______________________________________________ >> Pw_forum mailing list >> [email protected] >> http://pwscf.org/mailman/listinfo/pw_forum >> > > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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