[Pw_forum] question about output of SCF

[Paolo Giannozzi]

yumin qian wrote:

> I have done a scf calculation of ground state Pbnm CaCrO3 crystal , the 
> total band nbnd=101 
> there are 152 irreducible k-points  ,but the output file in X.save 
> directory only contians 76 folders : K00001-K00076

so there are 76 irreducible k-points, and since you are using
LSDA, the code doubles the number of k-points during the
calculation, so that you have 76 k-points for spin-up states
and 76 for spin-down. At the end, when results are saved,
spin-up and spin-down states are collected into a single
folder.

> I also do not know why we define Main grid and wavefunction grid 
> respectively ? Since the grid number are determined by the same 
> ecutwfc

not for USPP or PAW

> , could someone explain more clearly about the all the grids system 
> (include FFT grid, and charge density grid in real or G-space) in DFT ?

the best explanations I managed to produce are reported in
the 3rd paper listed here:
http://www.quantum-espresso.org/wiki/index.php/Ref:_First-principles_Molecular_Dynamics
You can get a copy here:
http://www.fisica.uniud.it/~giannozz/Papers/JCP_57.pdf

Paolo
-- 
Paolo Giannozzi, Democritos and University of Udine, Italy