[CP2K-user] How to check the convergence of ADMM

[ma...@gmail.com]

Hi,

I am a rookie in using cp2k. In my project I need to use HSE06 for a large 
system (1000 atoms) calculation. I have a few questions about using HSE06. 
Could somebody provide me some suggestions?
(1) In pure DFT calculations (such PBE), I can use MONKHORST-PACK kpoints 
scheme (e.g. 8 8 8) and run CELL_OPT calculations to get the optimized 
lattice parameters and then compare these parameters with literatures to 
confirm that the BASIS_SET and other settings used in the cp2k calculation 
are good enough to reproduce this sytem. However, in HFX calculations, it 
looks we can only use GAMMA kpoints scheme. The CELL_OPT with single kpoint 
can not get the correct lattice parameters. Then how can we confirm the 
BASIS_SET and setting in the cp2k calculations are accurate enough?
(2) HFX calculations are highly expensive so using ADMM approach is 
necessary. In the tutorial, it says "Always check the convergence of the 
primary and ADMM basis sets". I'm wondering what does this mean and how 
exactly should we do the check the convergence of the ADMM basis set? Or in 
another word, how do we usually choose which ADMM we use for our 
calculations?
(3) My material is Si, a semiconductor. I'm wondering is it possible that I 
can read the band-gap value directly from the output file after the SCF 
calcualtion?
I really appreciate it if somebody could provide some help.

Thanks&Regards,
Hongyang
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