[Pw_forum] A question about PSP Ti.pbe-mt_fhi.UPF and a general question about DFT+U in QE

[Paolo Giannozzi]

FHI pseudopotentials do not contain information on the reference atomic
configuration used in their generation. This is manually provided during
the conversion to UPF format. It looks like a mistake. Just exchange the
occupancies of 4p and 3d states: they are used only when generating the
starting charge for self-consistency, and as a check to prevent usage of
non-bound aromic states as Hubbard manifold.

Paolo

On Sun, Nov 27, 2016 at 2:42 PM, Hanghui Chen <chenhanghuipwscf at gmail.com>
wrote:

> To whom it may concern,
>     I noticed an anomaly with the psp Ti.pbe-mt_fhi.UPF in the library.
> Its valence configuration reads as:
>
>     nl pn  l   occ       Rcut    Rcut US       E pseu
>     4s  4  0  2.00      0.000      0.000     0.000000
>     4p  4  1  2.00      0.000      0.000     0.000000
>     3d  3  2  0.00      0.000      0.000     0.000000
>     4f  4  3  0.00      0.000      0.000     0.000000
>
>  I personally think the occupancy for 4p and 3d are incorrect. The correct occupancy might be 4p: 0.00 and 3d: 2.00. I am not sure whether this is indeed the correct psp or a bug in the psp. I want to double check with the community, since it is a psp converted from the Abinit web site.
>
>    A related question to this problem is that in the current implementation of DFT+U in QE, the occupancy for the 'correlated orbital' must have an occupancy larger than 0. Therefore for this psp of Ti, I can not turn on U on its d orbital. I am just curious, is "occupancy of the correlated orbital > 0" a strict condition? Can we make it "occupancy of the correlated orbital >= 0"? I manually changed the source code and it seems that there is no major difference as I have observed.
>
>   Thank you very much for your time.
>   Best regards.
>
> Hanghui Chen
> Assistant Professor of Physics
> New York University Shanghai
> Email: hanghui.chen at nyu.edu
>
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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