On Nov 20, 2007, at 15:55 , Cyrille Barreteau wrote: > Does anyone has experience about the behaviour > of the various diagonalization schemes? > Which one is better, in which case?
the so-called conjugate-gradient diagonalization basically never fails; it uses less memory but it is much slower than the block Davidson algorithm. The latter is also quite robust but there is a tiny probability to end up in the wrong ground state. The only such case I know happens in some high-symmetry perovskites, if you start from superposition of atomic states, with occupied states only, and if the phase of the moon is close to 42. The problem disappears if you add a few more states, or if you start from random wavefunctions. I am quite surprised to hear that there is a case in which you get good results with 12 states and bad with 20. I wouldn't be surprised by the opposite. Could you please post one jobs showing the problem? Paolo --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
