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.
