Sir, Stefano de Gironcoli Thank you For your kind reply. Yes i have tested my convergence issue but unable to figure out exactly which energy cut off and k point should i select. First i was tried with kpoint=gamma (0 0 0 0 0 0), for fast convergence and i obtained stress(Kbar)=0.24 at 95 Ry of ecut. The number of iteration is 8-9 in every case.
Convergence test at kpoint= 0 0 0 0 0 0 (gamma) ecut(Ry) stress(kbar) etot(Ry) 23 -856.12 -22.45678789 28 -816.21 -22.74277097 33 -717.31 -22.99913807 38 -640.04 -23.13068593 43 -538.05 -23.24446298 48 -388.44 -23.36265311 53 -298.19 -23.41743393 58 -228.34 -23.44939498 63 -147.46 -23.48057851 68 -107.24 -23.49317545 73 -81.19 -23.50039187 78 -48.03 -23.50793794 83 -22.26 -23.51292707 88 -10.40 -23.51479400 93 -3.80 -23.51569322 94 -2.96 -23.51578788 95 0.24 -23.51615658 96 0.24 -23.51615658 97 1.44 -23.51628362 98 1.44 -23.51628362 Second with taking kpoint in consideration again the stress was increased at fix ecut=95Ry. And if i decreased or increased the ecut from 95 Ry to 63Ry and 115Ry , the stress value increases and decreased very small respectively . Please see the below which i was mention above in wording. when cosider k point...fix ecut=95 k mess stress(kbar) etot(Ry) 1*1*1 0.24 -23.51615658 2*2*2 -107.01 -24.24731157 3*3*3 -146.30 -24.33808965 4*4*4 -149.74 -24.34988328 5*5*5 -149.91 -24.35200695 6*6*6 -149.97 -24.35245199 8*8*8 -149.85 -24.35256921 10*10*10 -150.01 -24.35257467 when we chnage the ecut 95 to 63::: 8*8*8 -279.21 -24.31814193 when we chnage the ecut= 115Ry::: 8*8*8 -142.60 -24.35372918 Please any suggestion will be appreciable. On Fri, Feb 24, 2012 at 1:45 AM, Stefano de Gironcoli <degironc at sissa.it>wrote: > ** > A norm conserving Nitrogen pseudo-potential is likely to require much more > that 28 Ry. > have you studied the convergence of your calculated energy and stress with > respect to cutoff and k-point sampling ? > > Stefano de Gironcoli > > On 02/23/2012 07:41 PM, bramha pandey wrote: > > Dear all QE users and developers.. > > I want to calculate the property of system at T=0 K and at P=0 kbar at > starting of my pw.x run. > But at the end of run, i obtained force=0 but stress p =-832.77 kbar. > I am afraid of this stress value. my input file is given below. > > &CONTROL > calculation = 'scf' , > restart_mode = 'from_scratch' , > outdir = '.' , > pseudo_dir = './' , > prefix = 'aln' , > tstress = .true. , > tprnfor = .true. , > / > &SYSTEM > ibrav = 2, > celldm(1) = 8.285, > nat = 2, > ntyp = 2, > ecutwfc = 28 , > / > &ELECTRONS > conv_thr = 1.0d-8 , > mixing_beta = 0.7 , > / > ATOMIC_SPECIES > Al 26.98000 Al.pz-vbc.UPF > N 14.01000 N.pz-vbc.UPF > ATOMIC_POSITIONS alat > Al 0.000000000 0.000000000 0.000000000 > N 0.250000000 0.250000000 0.250000000 > K_POINTS automatic > 4 4 4 0 0 0 > > Any type of help is highly appreciated. > > > > > > _______________________________________________ > Pw_forum mailing listPw_forum at > pwscf.orghttp://www.democritos.it/mailman/listinfo/pw_forum > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- Thanks and Regards Bramha Prasad Pandey GLA University, Mathura. INDIA. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120225/2b85bf2a/attachment.htm
