[CPMD-list] pseudopotential validation

[Axel Kohlmeyer]

On Wed, 16 Feb 2005, Young Min Rhee wrote:

YMR> Hi,
YMR> 

dear young min,

YMR> Usually, README files of almost all pseudopotential files say that
YMR> users have to validate the pp for the given problem, but how can I
YMR> test it? I mean what's the way to validate whether the PP is good or
YMR> not?

pseudopotentials are usually created from (radial) all-electron
calculations of a neutral configuration of a single atom. in many
compounds, the oxidation state changes, so you should test, whether the
pseudopotential represents the properties of the respective atom in that
oxidation state well enough for your purposes.

this can be done (in part) while creating the pseudopotential,
where you can compare the eigenvalues of the valence states
of the pseudopotential (after you have created it) in different
oxidation states with the corresponding all-electron calculations.

another test is to compare optimized geometries of (small) molecules
which are similar to your intended compound from a CPMD calculation
with an all-electron calculation using the same DFT functional.

finally, you can try to reproduce already published results.

you also have to check, how large a plane wave cutoff you need, 
e.g. whether your optimized geometries (or forces, if you are lazy) 
change significantly if you increase the cutoff.

regards,
	axel.

YMR> 
YMR> Thank you!
YMR> Young Min

-- 

=======================================================================
Dr. Axel Kohlmeyer   e-mail: axel.kohlmeyer at theochem.ruhr-uni-bochum.de
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum  http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.