Dear colleagues, I have found strange differences in results for the calculation of pressure using pwscf in versions 4.3 and 5.0.N (N=1,2). We are calculating wurtzite CdSe, using the following UPF files.
PAW calculation Cd 112.40000 Cd.pbe-dn-kjpaw_psl.0.2.UPF Se 78.96000 Se.pbe-n-kjpaw_psl.0.2.UPF Ultrasoft PP calculation Cd 112.40000 Cd.pbe-dn-rrkjus_psl.0.2.UPF Se 78.96000 Se.pbe-n-rrkjus_psl.0.2.UPF For the PAW calculations, the convergence of pressure with the density cutoff (euctrho) shows jumps (see the attached figure paw-press.eps) and no convergence in the case of version 5.0.N, while there is convergence with version 4.3. For both versions the total energies are the same. The jumps are associated with differences in the number of symmetry operations detected. The message " (note: 6 additional sym.ops. were found but ignored their fractional translations are incommensurate with FFT grid)" is associated with higher pressures (33 kbar). Lower pressures ~ 26 kbar) are found when the FFT grid is commensurate and all 12 sym. ops. are used. In the calculations with version 4.3 the pressures are somewhat lower, but apparently convergent. Also, there are less symmetry operations detected or used than for version 5.0.N. In the ultrasoft calculations, (see figure uspp-press), both versions 4.3 and 5.0.N produce convergent pressures vs ecutrho, but the pressures differ almost by 10 kbar. (The total energies are almost equal, as expected). Thanks for any comment. -- Eduardo Menendez Proupin Departamento de Fisica, Facultad de Ciencias, Universidad de Chile URL: http://fisica.ciencias.uchile.cl/~emenendez *"Lograremos el anhelado desarrollo cuando sea la ciudadan?a, y no los cient?ficos, la que pida m?s ciencia para Chile." J. Babul* -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20130401/1b38bdb9/attachment.html -------------- next part -------------- A non-text attachment was scrubbed... Name: uspp-press.eps Type: application/postscript Size: 18308 bytes Desc: not available Url : http://pwscf.org/pipermail/pw_forum/attachments/20130401/1b38bdb9/attachment.eps -------------- next part -------------- A non-text attachment was scrubbed... Name: paw-press.eps Type: application/postscript Size: 18598 bytes Desc: not available Url : http://pwscf.org/pipermail/pw_forum/attachments/20130401/1b38bdb9/attachment-0001.eps