[Pw_forum] Re: vanderwaals

[Sandro Scandolo]

Nichols,

unfortunately this is not the vdW functional of Langreth et al.

It is a much simpler procedure to correct the DFT forces and stress 
for the missing 1/R^6 tail. It consists of adding to the DFT forces 
and stress a classical interatomic force field that decays at long 
distances like 1/R^6 (with the appropriate C6 coefficients), and 
vanishes at "short" distances, i.e. at interatomic distances where 
one expects DFT to give the correct forces. This is done in a smooth 
fashion, of course. It requires a cut-off distance, a smoothing 
parameter, and the C_ij coefficients for any pair i,j of species.
The present implementation is system-specific (for a C-H saturated
system) but can trivially be extended for any system. More details 
can be found in S. Serra et al, Chem Phys Lett 331, 339 (2000)

Regards,
Sandro

*

From: Nichols A. Romero* <mailto:pw_forum%40pwscf.org>
/Mon, 3 Apr 2006 10:46:19 -0400/

Hi,

In CP source, there is a file called
vanderwaals.f90

Is this the vdW functional of D. Langreth et. al?

Bests,
--
Nichols A. Romero, Ph.D.
1613 Denise Dr. Apt. D
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