[CPMD-list] PW91 implementation

[Axel Kohlmeyer]

On Wed, 25 Feb 2004, Oleksandr Shepelyev wrote:

OS> Dear CPMD Users!
OS> 
OS> I want to implement the PW91 (GGA) density functional into CPMD.
OS> I want to use Vanderbilt PW91 pseudo-potentials. I did not find
OS> a PBE pseudo-potentials for my atoms. So I thought that I can use

dear oleksandr,

it might be much easier, if you would recreate the PW91 pseudo-potentials
for PBE, since the two functionals are so similar. as you can see
from the vanderbilt pseudopotential code, the parameter exfact determines
the functional. of course you will have to carefully check and test
the new pseudopotentials, but since you seem to be starting a new
project, you would have to do this anyway.

hope this helps,
	axel kohlmeyer.

OS> PBE part of code in lsd_func.F as an example. The Perdew-Wang 1991
OS> GGA Correlation Functionals are the same in PBE and PW91. The PBE
OS> Exchange Functional and The Perdew-Wang 1991 GGA Exchange Functional
OS> are different in potential F(S) only.
OS> 
OS> But I found that the description of potential F(S) in lsd_func.F is
OS> slightly different from the PBE functional described by John Perdew.
OS> In the PhysRevLett F(S)=1+R-R*(1+m*S^2/R)^-1
OS> But in code the first constant 1 is omitted: F(S)=R-R*(1+m*S^2/R)^-1
OS> 
OS> Also it is not easy for me to understand how the partial derivatives
OS> V1X and V2X was obtained. I found in the code that V1X=dE/drho and
OS> V2X=1/grad(rho) * dE/grad(rho), but...
OS> 
OS> Any help is much appreciated!
OS> 
OS> Sincerely yours,
OS> 
OS> Alex Shepelyev
OS> _______________________________________________
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OS> 
OS> 

-- 


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Dr. Axel Kohlmeyer                        e-mail: axel.kohlmeyer at rub.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/
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