[Q-e-developers] on the calculation of Hubbard U values

[José C. Conesa]

Dear QE developers,

I have seen in the last Psi-K highlight about the advances in the QE 
code that version 6.2 (now at a release candidate status) will allow 
computing ab initio U values for the DFT+U scheme using DFpT, so that 
supercells would not be needed and the process would be much easier. 
Then, if one wants to find U values considering the responsenot only for 
a specific element but for all of them present in the material, i.e. 
computing the complete (inverse) susceptibility matrices, it is 
necessary that Hubbard parameters be considered for all elements in the 
material. But in its present version, the code in files 
Modules/set_hubbard_l.f90 Modules/set_hubbard_n.f90 and PW/src/tabd.f90 
only allows using Hubbard parameters for part of the elements in the 
periodic table.

For this reason I wish to make you a request: please include in those 
files, in the final qe-6.2 version, all elements in the periodic table 
(well, you may omit noble gases) so that each user does not need to 
modify those files, and compile the executables again, every time that 
(s)he has to consider a new element in the material for which U values 
should be computed. This should not be difficult to do. I am aware that 
in some cases it may be not clear which atomic subshell should be 
affected by the Hubbard correction; for example, La might need to do it 
for d or f orbitals depending on the compound, and In or Zn might be in 
a similar problem for p and d orbitals. This could be solved just by 
adding a word of caution in the manual.

Hoping that this modification may be made,

Best wishes,

-- 
José C. Conesa
Instituto de Catálisis y Petroleoquímica, CSIC
Marie Curie 2, Cantoblanco
28049 Madrid, Spain
Tel. (+34)915854766

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