Dear Jacopo, The g vectors that are used respect the cutoff condition |k+G|^2 < ecutwc/hbar, this defines a sphere (per k point). The box, used for the FFT, is the smallest that contains all spheres.
Kind regards -- Lorenzo Paulatto Written on a virtual keyboard with real fingers On 26 May 2017 2:48 a.m., "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 >
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