[CPMD-list] combination of PBE USPP with BLYP DFT

[Erik Emilio Santiso]

Hi! Well, this looks more like a coincidence than anything else. I don't
think it makes any sense to find a PP with one xc functional and then do
the calculation with another one. What happens if you use the PBE PP's
with the PBE functional?

Erik.

On Thu, 30 Oct 2003, Jung Goo Lee wrote:

> Hi everyone,
>
> I would like to know whether the combination of PBE uspp in ATOMS option
> and BLYP in DFT
> option (the example of partial input is shown below)makes sense or not,
> especially, for calculations
> of free energy (constraint). This is because BLYP method underestimate
> the dissociation free energy
> compared with experiment. For example,  water dissociation in 32 water
> molecules with MT PP/
> BLYP method gave 17 kcal/mol in free energy while experimental value is
> 21 kcal/mol(Trout and
> Parrinello, Chem. Phys. Lett, 288(1998)343.
> I tried the same calculation with PBE uspp and BLYP method.
> I got about 20 kcal/mol althogh I tried with  a few hundred fs (instead
> of 1 ps) MD at each point of
> O-H bond constraint. So, this combination (PBE uspp/BLYP) seems to be
> o.k. in free energy
> calculations.
>
> Is this a reasonable and cheap(computationally) way to get out of the
> problem with free energy
> calculations with gbl uspp/BLYP?
> Does any one have any rationalization or contradiction with reasonable
> explanation?
>
> Jung-Goo Lee
>
> Example
> --
> --
>  &ATOMS
> *008-O-gpbe--bm.uspp NEWF BINARY
>   LMAX=P
>   1
>   4.3728  4.5000  4.5000       1   8
>
> *001-H-gpbe--bm.uspp NEWF BINARY
>   LMAX=S
>   2
>   5.5172  4.5000  5.9238       1   1
>   5.5172  4.5000  3.0761       1   1
> &END
>
> &DFT
>  OLDCODE
>  FUNCTIONAL BLYP
>  GRADIENT CORRECTION BECKE88 LYP
>  LDA CORRELATION LYP
> &END
> --
> --
>
>
> _______________________________________________
> CPMD-list mailing list
> CPMD-list at cpmd.org
> http://www.cpmd.org/mailman/listinfo/cpmd-list
>