[Q-e-developers] B3LYP in QE

[Michael Banck]

Hi,

On Tue, Nov 03, 2015 at 01:48:57AM +0000, nisihara225 at gmail.com wrote:
> I am developing both Gaussian basis-set software and plane-wave software,
> 
> thus, I am more or less familiar with B3LYP.
> 
> Let me explain VWN functionals in B3LYP.
> 
> 
> The original B3LYP is defined with VWN-5 (A.D.Becke, J. Chem. Phys., 107, 8554 (1997)).
> 
> And almost all of quantum chemical softwares (with Gaussian basis-set) adopt VWN-5.

Well, almost all adopt at least VWN-5.  Most have a secondary identifier
for the other one, like B3LYP-G or B3LYP3 or so.
 
> However, some softwares use other VWNs.
> 
> For examples, Gaussian09 uses VWN-3, NWChem uses VWN-1-RPA.

As I understand it, VWN-1-RPA and VWN-3 are the same, see e.g. the first
answer at
http://scicomp.stackexchange.com/questions/21/how-is-b3lyp-implemented-in-gaussin-0-gamess-us-molpro-etc

"This selects B3LYP with VWN formula 1 RPA local correlation which, to
the best of my knowledge, is identical to what they call VWN formula III
in some other programs (like Gaussian 03)."

> If you want to implement Becke’s 3-parameter formulation,
> 
> I recommend to adopt VWN-5 or some VWNs can be selected.

I think it would be best to have a second alias like "B3LYP-G" which
lets people compare with Gaussian etc.  But then, it's not a big issue.


Michael