Dear Jiayu Dai the Baldereschi point and MP points are efficient choice because they exploit the SYMMETRY properties of the system in order to sample the BZ on a hopefully small set of points. In liquid and disordered materials there is no symmetry and therefore there is no symmetry-related k-point reduction and any regular grid of points should be equally efficient. On the other hand for large systems the BZ shrinks and the refolded bands in the mini-BZ are almost flat which means that any single point in the BZ should do the work. In this situation Gamma is convenient because wfc (in absence of spin-orbit) can be chosen as real in real space which implies that wfc Fourier components of G and -G are related by complex conjugation and you can use half the memory storage and cut by two the number of operations.
best, stefano Jiayu Dai wrote: > Dear users, > > I have a question about the sample points in the Brillouin zone. We usaually > use > the MP point in our calculations, and it works well and fast in cubic crystal. > However, for disordered materials or liquids, we usually use Gamma point only, > such as point in CPMD. My question is how do we know the Gamma point is better > than the Baldereschi mean value point, or on the contrary??Which one gives > faster > convergence? > > Thanks a lot. > > Jiayu > > > > > ------------------------------ > ------------------------------------------- > Jiayu Dai > Department of Physics > National University of Defense Technology, > Changsha, 410073, P R China > ----------------------------------------- > > ------------------------------------------------------------------------ > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
