[Q-e-developers] Divergence in PAW UPF

[Lorenzo Paulatto]

Dear Ilia,
when constructing a pseudopotential with multiple projectros, be it PAW, US or 
normconserving, you build the second projector over a scattering state (which 
we usually just call wavefunction, for simplicity) of the isolated atom 
hamiltonian. A scattering state solves the usual Sschroedinger equation:
H\psi = e \psi
for an energy e which is not an eigenstate of H.

Scattering states are not normalizable: they always diverge. The only special 
thing about PAW, is that these states are solved in the UPF files, while for US 
and NC they are not.

In PAW we rely on the fact the pseudo and all-electron wavefunctions/
scattering state are identical after a certain radius, hence instead of 
integrating up to infinity we stop at the cutoff radius.

I see no solution for your problem, I' afraid you'll have to review your 
definition of the Dij matrix.

kind regards


On Friday, 13 May 2016 14:49:10 CEST Ilia Sivkov wrote:
> Dear All,
> 
> Recently I started to dig a code of Quantum Espresso to compare it with
> the developed in our group and found that many PAW UPF files have
> divergence in AE and PS radial wave functions. I found that it appears
> mostly in 4th P-orbital. Here I post two plots with these AE radial
> functions for V and Cu
> 
> Looking at the other files I found such problem in each of them. It
> seems that all PAW UPF files have such divergence.
> 
> Interesting point, that Quantum Espresso gives no bad values in density
> (variable "rho_lm") and potential (hartree, xc, total), but variable
> "pfunc" has such divergense.
> 
> Due to these divergences our developing code gives bad values in Dij
> matrix, because it is calculated in a little bit different way.
> 
> I would be very appreciated if you could help me to explain such strange
> behavior.
> 
> With best regards,
> Ilia Sivkov


-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
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