[CP2K-user] How to understand/tune parameters for GAPW calculations
Natalie Holzwarth
nat... at wfu.edu
Tue Apr 14 15:16:07 UTC 2020
Dear cp2k developers,
We are very much looking forward to possibly using CP2K particularly
using the GAPW scheme to extend our calculations which up to now have been
performed using ABINIT and QUANTUM ESPRESSO using PAW. We have tried a
number of your tutorials and test inputs, but are have a hard time
understanding how to properly pick the parameters. Is there perhaps a
writeup somewhere that describes the detailed implementation or perhaps a
list of the main subroutines that a user should study? Or perhaps someone
might have time to answer some the following silly questions.
1. These questions are based on the notion that we should use the
all-electron bases since these would allow n^1 to be represented
analogously to Blochl's PAW formulation. Is this the correct way to think
about it?
2. According the paper by Lippert et al (1999), the soft wavefunctions
and densities are chosen by eliminating the Gaussian basis primitives with
too large an exponent. Which of the input parameters determines the soft
basis parameters?
3. In addition to the soft density, Blochl's PAW scheme has a local
pseudo potential. I am not sure what is the analogous local pseudo
potential for GAPW and which parameter controls it. I have assumed that we
should use "ALL" potentials in the input files. Is this correct?
4. Some of the examples use the following parameters which seem to be
important, but I am not sure how to choose them
MAX_RAD_LOCAL
ALPHA0_H
*HARD_EXP_RADIUS*
*5. *Is there a provision/recommendation to use the frozen core
approximation and if so, what parameters control that?
Thanks in advance for any suggestions you can provide and much gratitude
for sharing and maintaining the cp2k software package.
Sincerely, Natalie Holzwarth
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