Dear Lily, Indeed the non magnetic ground state of iron is fcc therefore if you start from bcc your system is very unhappy. As suggested by Mike you should set nspin=2. However do not forget that by doing vc-md you will move atoms according to a given "molecular" temperature but you will totally ignore the spin temperature which is another complicated story:-) Any hint to do a spin+molecular dynamic from ab-initio would be very welcome:-) Some attempts to do it from empirical models have been proposed but this remains rather tricky.
good luck.. cyrille ============================================================ Cyrille Barreteau phone : +33 (0)1 69 08 29 51 CEA Saclay cellphone: +33 (0)6 47 53 66 52 IRAMIS, SPCSI, Bat. 462 fax : +33 (0)1 69 08 84 46 91191 Gif sur Yvette Cedex email: cyrille.barreteau at cea.fr FRANCE ~~~~~~~~~~~~~~~~~~~~~~~~ Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/ ============================================================== ________________________________________ De : pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] de la part de Mike Mehl [Michael.Mehl at nrl.navy.mil] Date d'envoi : lundi 5 d?cembre 2011 15:36 ? : Lily Anh; PWSCF Forum Objet : Re: [Pw_forum] vc-md temperature increases Since BCC Fe is magnetic, I suspect you will get better results by adding nspin=2, to your &system block. On 12/05/2011 04:13 AM, Lily Anh wrote: > Hi all, > > I am running a 'vc-md' calculation with PW.X in QE v4.1.1. The system is > bcc-Fe supercell of 16 atoms. The target temperature were set to 600 K > in the input file while the temperature goes up all the way to more than > 1000 K. I tried with a much larger supercell (128 atoms), this problem > still happens. > > Does anyone know how to fix this? > > Many thanks! > Lily > > > > I attached my input file here: > > &system > nosym=.t., ibrav = 0, celldm(1) =9.3,nat= 16, nbnd=300,ntyp= 1, > ecutwfc=40,ecutrho=400,occupations='smearing', smearing='mp', degauss=0.02 > / > &electrons > mixing_mode='TF' > mixing_beta= 0.7 > / -- Michael J. Mehl Head, Center for Computational Materials Science Naval Research Laboratory Code 6390 Washington DC _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
