On Oct 22, 2009, at 21:29 , Brad Malone wrote: > Hi, I'm trying to calculate a large number of conduction band > states for cubic Si (to be used in a subsequent GW calculation). > However, when doing this I sometimes run into errors like > "problems computing cholesky decomposition" or "too many > bands are unconverged".
the algorithm used in PWscf is based on the assumption that the number of Kohn-Sham states (aka bands) is much smaller than the number of basis functions (i.e. plane waves). If this assumption doesn't hold (and it doesn't if you calculate 500 bands in fcc Si unless you use a very large cutoff) you may run into trouble. Moreover iterative diagonalization becomes slower and more memory-consuming than conventional diagonalization. If you really need to do that, you need to modify the code Paolo --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
