Dear Xijun, Thanks very much for your advice. I will do the necessary changes and let you know how things go. Regards Elie
> Date: Wed, 7 Sep 2011 15:58:37 -0400 > From: xijunw at gmail.com > To: pw_forum at pwscf.org > Subject: Re: [Pw_forum] problems with vc-relax > > On Wed, Sep 7, 2011 at 3:28 PM, Elie Moujaes <elie.moujaes at hotmail.co.uk> > wrote: > > Dear all, > > > > Dear Elie, > > > > > I am relaxing a 60 atom supercell (graphene grain boundary) to make the > > total force on atoms mainly 0.001 Ry/au. However the vc-relax stopped after > > 4 days of execution and without reaching the desired force threshold. The > > following output was obtained : > > > > Please can anyone advice me on this? Shall I start with the new > > configuration and start relaxing again? > > > > I'm also doing some cell relaxation. As I understand, cell > optimization is not very easy, and it is common that it does not > converge after a very long run. > > Surely you should restart the calculation to achieve your convergence > criteria. You can just change the "restart_mod = 'from_scratch' " to > "restart_mode = 'restart' ", and submit the job again to continue from > where you stopped. Please be advised that pw.x will read cell > parameters / atomic positions, initial density, pseudopotentials from > the folder of GBphonon.save, so make sure you copy the folder to > computing-nodes. > > However, I highly suggest you do something to accelerate the > convergence. For example, if you do not expect the cell angle to > change (i.e. keep angles=90), you may add the following keywords to > the &CELL section. > > cell_dofree = xyz > > This will greatly reduce the uncertainty of the geometry optimization. > and reduce energy/force oscillation. > > Another great idea is to manually choose x, y and z, then do a > relaxation of atomic positions only. and plot the total energy changes > with x, y and z. However, be noted that different volume means > different numbers of PW basis function, and energy comparison in this > way could be a little confusing. Anyway, if volume change is not > large, still this would help a lot. > > Since I'm also a learner, any more comments or correction to my > comments are welcome. Thanks > > Xijun > > > > > Regards > > > > > > > > Elie Moujaes > > > > University of Nott > > > > University Park > > > > NGT 3RD > > > > > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://www.democritos.it/mailman/listinfo/pw_forum > > > > > > > > -- > Department of Chemistry and Biochemistry, Concordia University > 7141 Sherbrooke Ouest, Montreal, QC H4B 1R6 > Tel: 514-848-2424-#5835 (Lab) TA office: SP175.23 > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110907/d18c2aa9/attachment.htm
