[Q-e-developers] recompute the total energy after scf is finished

[Lorenzo Paulatto]

On 11/04/2013 03:39 PM, stefano de gironcoli wrote:
> one option would be to perform a nscf calculation then..
>
> -read rho
> -compute v_of_rho
> -diagonalize H_KS => new wfc new eigenvalues
> -compute the energy (new calculation of exc, ehartree needed)
>
> an alternative would be to compute the single particle contributin to
> the total energy not from the eigenvalues
> but directly from \sum f_i <psi_i| T + V_ext| psi_i>
> this should be equivalent to eband+deband without the need to know what
> v(r) was.

This looks like the best way to do it, if I'm not wrong it is enough to 
call g2kin then vloc_psi_{k,gamma} then bracket and sum, divide by 
omega. Probably half a dozen terms will still be missing (add_vuspsi?), 
but I'll find them.

Let me know if you think this bit of code can be of general interest, 
otherwise I won't commit it as it would only create more entropy.

cheers and thanks



-- 
Dr. Lorenzo Paulatto
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