Please provide the input. This should not happen. Andrea
On Tue, 2010-07-13 at 11:07 +0200, Julen Ibanez Azpiroz wrote: > Hello > > I would like to make a question to anyone who has experience in using > the spin-orbit coupling (SOC). My problem is as follows: > > > I relax a structure WITHOUT including SOC by the method damped > dynamics: > > > / > &IONS > ion_dynamics = "damp", > pot_extrapolation = "second_order", > wfc_extrapolation = "second_order", > / > with the time interval dt=20, and I get a structure where the forces > are <1.0D-4Ry/au. Lets call this structure A. > > Now, I include the SOC, and I run an scf calculation with structure A. > It turns out that there are quite big forces, of the order of > 0.01Ry/au. The energy of the unit cell with structure A and SOC > included is -207.10202515 Ry. > > Then, I try to relax the forces with SOC included with the same method > as before. It relaxes (forces<1.0D-4), but in a structure quite > different form A; lets call this new structure B. The surprising thing > is that now, in structure B, the energy is -207.08231311 Ry, higher > than with structure A. To summarize: > > Calculations with SOC included: > > Structure A-> -207.10202515 Ry, forces of the order of > 0.01Ry/au > Structure B-> -207.08231311 Ry, forces <1.0D-4Ry/au > > Besides, if I plot the energies of the different structures that go > from A to B when relaxing with SOC included, I see that the energy > increases in each step going from A to B, and the energy of A seems to > be in the botttom of a parabola. So, everything suggests that > structure A is the most stable structure even when SOC is included, > except there exist forces. I have checked the convergence with respect > to the cutoff and the k point mesh, and I have used the same > parameters in the calculations without SOC and with SOC. > > I do not know how the forces are calculated when SOC is included, and > I do no know who to trust, the energy or the forces. I will apreciatte > very much any help, thank you in advance > > > Julen Iba?ez Azpiroz > > University of the Basque Country > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -- Andrea Dal Corso Tel. 0039-040-3787428 SISSA, Via Beirut 2/4 Fax. 0039-040-3787528 34151 Trieste (Italy) e-mail: dalcorso at sissa.it
