Only plane waves with \hbar^2(k+G)^2/(2m) < Ecut are included. The regular grid in G-space must be large enough to include all of them, but it also includes a significant amount of plane waves that exceed the cutoff.
Paolo On Fri, May 26, 2017 at 2:46 AM, Jacopo Simoni <[email protected]> wrote: > Dear PWSCF users, > > I am doing a simple scf calculation for a system of 100 Hydrogen atoms in a > simple cubic cell. > > I am generating the wave functions with wf_collect=.true. for a single K > vector (0,0,0). > > From the scf output I realized that the total number of G vectors printed on > the file is 847. I am using ecutwfc=20.0 and the shape of the Kohn-Sham > matrix is > > Kohn-Sham wave functions dimensions=(847, 52) > > where 52 corresponds to the number of bands that I am using in the > calculation. > > However, I am wondering why in the gkvectors.xml file I have a list of G > vectors ranging between -5 and 5 times 2*pi / a (a is the lattice parameter) > along each primitive lattice direction. > > The total number of points in such a regular grid should be 11*11*11 = 1331 > that is clearly different from 847. What is the meaning of the missing 484 G > vectors in the grid ? I am a bit confused could you please explain to me > these results ? > > Many thanks in advance, > > Jacopo Simoni, > Los Alamos National Laboratory > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
