[Wien] EV GGA and property calculation

[Fred Nastos]

On November 29, 2004 01:55 am, Dr. Sharat Chandra wrote:
> Dear Wien Members
>
> 	We know that Engel-Vosko GGA gives the correct band gaps but the
> total energies are unreliable.

The band gaps from Engel-Vosko are _sometimes_ better
than LDA; they are not always correct.  For GaAs for example, I
find a band gap around 1.1 eV with EV, and approximately 0.3
for LDA.  Both values are still significantly off from the experimental.
I think more studies need to be done to claim that EV gives better
band gaps all the time.

> So, if we have a EV converged SCF calculation, we can calculate
> optical properties with it, but for calculating other properties such
> as X-ray spectrum etc., we should use the PBE GGA SCF
> calculations?

I think the accepted approach is to make an SCF calculation using
LDA or GGA, and then only calculate the spectra via the EV functional.

> Any comments?
>
> Regards and Thanks in advance
> Sharat Chandra