Thank you for your reply. Do you mean that I can neglect this numerical error?
2009/4/8 Axel Kohlmeyer <akohlmey at cmm.chem.upenn.edu> > On Wed, 2009-04-08 at 19:01 +0800, ??? wrote: > > Dear Pwscf users, > > I did a variable cell calculations for a base centered > > monoclinic crystal. The cell displayed in xcrysden is correct, and > > PWscf can find the symmetry. However, in the optimizing process, the > > cell parameter changed unexpectedly, which may be wrong. In the > > no. it is most likely not wrong, but rather an indication of the > level of numerical accuracy with which you computed your forces > and stress tensor. > > cheers, > axel > > > user's guide of PWscf, the base centered monoclinic cell is defined > > as follows: > > base centered monoclinic > > ============================= > > v1 = ( a/2, 0, -c/2), > > v2 = (b*cos(gamma), b*sin(gamma), 0), > > v3 = ( a/2, 0, c/2), > > where gamma is the angle between axis a and b > > ============================= > > In the first step of optimize process, the cell is changed as > > following: > > CELL_PARAMETERS (alat) > > 0.483414893 0.003687739 -0.271981740 > > -1.013180906 0.556415406 0.000000000 > > 0.483414893 0.003687739 0.271981740 > > My question is : why the quantities of second row of v1, v3 vector do > > not retain zero! > > > > Any suggestion and comment is appriciated. Thank you in advance! > > > > The input file is attached! > > &CONTROL > > title = 'c2', > > prefix = 'li', > > calculation = 'vc-relax' , > > restart_mode = 'from_scratch' , > > outdir = './' , > > wfcdir = './' , > > pseudo_dir = './' , > > tstress = .true. , > > tprnfor = .true. , > > etot_conv_thr = 1.0D-5, > > forc_conv_thr = 1.0D-4, > > / > > &SYSTEM > > ibrav = 13, > > celldm(1) = 14.7756, > > celldm(2) = 1.20528, > > celldm(3) = 0.56348, > > celldm(4) = -0.873177, > > nat = 12, > > ntyp = 1, > > ecutwfc = 200, > > nosym = .false. , > > / > > &ELECTRONS > > electron_maxstep = 100, > > conv_thr = 1.D-10, > > / > > &IONS > > ion_dynamics='bfgs', > > / > > &CELL > > cell_dynamics='bfgs', > > press=900, > > / > > ATOMIC_SPECIES > > Li 6.914 Li.pz-s-mt.UPF > > ATOMIC_POSITIONS (crystal) > > Li -0.46080 0.21740 1.49640 > > Li -0.02770 0.02590 1.28350 > > Li -0.80760 0.63690 0.91840 > > Li 0.23010 0.43900 0.29270 > > Li 0.06870 0.87600 0.40410 > > Li -0.04760 0.70260 1.56000 > > Li -1.49640 -0.21740 0.46080 > > Li -1.28350 -0.02590 0.02770 > > Li -0.91840 -0.63690 0.80760 > > Li -0.29270 -0.43900 -0.23010 > > Li -0.40410 -0.87600 -0.06870 > > Li -1.56000 -0.70260 0.04760 > > K_POINTS automatic > > 8 8 8 1 1 1 > > > > -- > > Y. C. Cheng > > Department of Phyics > > Nanjing University > > Nanjing 210093 > > P. R. China > > Tel: 86-25-83592907 > > Email: yccheng.nju at gmail.com > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://www.democritos.it/mailman/listinfo/pw_forum > > -- > ======================================================================= > Axel Kohlmeyer akohlmey at cmm.chem.upenn.edu http://www.cmm.upenn.edu > Center for Molecular Modeling -- University of Pennsylvania > Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323 > tel: 1-215-898-1582, fax: 1-215-573-6233, office-tel: 1-215-898-5425 > ======================================================================= > If you make something idiot-proof, the universe creates a better idiot. > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Y. C. Cheng Department of Phyics Nanjing University Nanjing 210093 P. R. China Tel: 86-25-83592907 Email: yccheng.nju at gmail.com -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20090408/f1d82251/attachment.htm
