In data 30 giugno 2009 alle ore 13:27:20, Huiqun Zhou <hqzhou at nju.edu.cn> ha scritto: > BTW, there are other items need to check: > (1) ion_dynamics > add 'bfgs' for the case of calculation = 'vc-relax'
This is already fixed in cvs, actually BFGS is the default case now, even for vc-relax. > (2) pot | wfc_extrapolation > please clarify if 'first_order', 'second_order' can be used in > calculations other than 'md' or 'vc-md'. I used these options in > 'relax' and 'vc-relax' without any errors, too. Of course, I don't know > if these were really in > effect. Both can be used for non-dynamical optimization (such as BFGS), although they don't striclty make very much sense. Nevertheless, they can help speeding up convergence, especially when the minimization steps get smaller. I would need to consult Paolo Giannozzi (who implemented the extrapolation) to be 100% sure. > (3) ecfixed, qcutz and q2sigma > in the original paper, the framework is an extension of PR dynamics to > CP. Please clarify if these are effective in other dynamics (damp-w, > bfgs). If possible, suggest a guide line how to set these options > (there is only one example of carbon in the paper), say, qcutz should > be at least N (2?) times of ecfixed, ecfixed should be ecutwfc plus > alpha (5 Ry or so?), > q2sigma should be one N-th of qcutz ... They are used to compute a correction to the stress tensor, hence the apply to all kind of variable-cell processes (if it makes sense or not, I really cannot say). regards -- Lorenzo Paulatto SISSA & DEMOCRITOS (Trieste) phone: +39 040 3787 511 skype: paulatz www: http://people.sissa.it/~paulatto/ *** save italian brains *** http://saveitalianbrains.wordpress.com/
