[QE-users] Wrong electron number in superposition of atomic charge densities

[Colonna Nicola (PSI)]

Dear QE experts,


 I recently perfomed a scf PBEsol calculation for Tb2Ti2O7 (attached the input file).

 I would like to plot the difference between the scf charge density and the superposition

 of atomic charge. For this purpose I used the PostProcessing tool (plut_num = 9).


 I expected the integral of this difference to be ~0 , but I found it to be 4. After a quick check

 I realized that the Ti pseudopotetial (GBRV-1.4, ti_pbesol_v1.4.uspp.F.UPF) was generated

 in an ionized configuration with just 1 electron (instead of 2 ) in the  3d orbital. Since there

 are 4 Ti in the primitive cell, I think this is the reason for the odd result described above.


 Indeed during the initialization of a scf calculation for an isolated Ti atom I got:



Initial potential from superposition of free atoms
     Check: negative starting charge=   -0.001319
     starting charge   10.99996, renormalised to   12.00000


 However this renormalization is not done in the PP, and in any case I do not think it would make sense there.


 That said, my feeling is that I cannot completely trust the charge density difference.

 Do you have any advise on how to solve this problem (beside changing pseudo)?


 Thank you in advance and best regards,


Nicola Colonna



-----------------------------------------------------
PAUL SCHERRER INSTITUT
Nicola S. Colonna
WHGA/150
CH-5232 Villigen-PSI
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