[Pw_forum] V pseudopotential

[Giuseppe Mattioli]

I don't have any V normcons pseudo for you, but I still would share some 
results. I'm trying to study a 6 atom rutile TiO2 cell with the pbe0 hybrid 
functional (48 electrons, convergence achieved by using a k444 grid in the 
case of the pbe xc). Honestly, I didn't understand how to deal with the q grid 
in the case of periodic systems (the nqx variables. In the case of molecules I 
managed to have fine results by using the gamma point and a 111 q grid), then 
I tried different grids (q111, q222, q444). The q111 case requires reasonable 
resources but doesn't provide reliable results. The q222 case is already very 
expensive and the achieved results are still not very good. I regard a lattice 
parameter optimization in this case as a "bath of blood" (dunno if you say 
something similar...:-)). The q444 case... don't do it, please. I suspect that 
V oxide cells are larger, so work harder on the DFT+U calculations...

However, look (more than two seconds) at the /yourespresso/atomic_doc/ 
directory. It should be really easy to generate a norm conserving V 
pseudopotential. Then, make several tests in order to say if your 
pseudopotential is a good one (and this is a little more difficult). It is 
indeed one of the more instructive tasks if you want understand (on a 
practical basis) how to perform reliable calculations.

Yours
Giuseppe


On Monday 06 July 2009 18:41:33 Jun Dai wrote:
> Dear all,
> I want to have a try of the hybrid functional implemented in Q-E for a
> vanadium oxide system, since the LDA+U failed to give reasonable results,
> and the ultrasoft pp seems not supported yet, so can someone share a copy
> of norm-conserving V pseudopotential with me? Thanks in advance.
>
>
>
>
> ------------------------------
> Best regards,
> Jun Dai
>
> =============================================================
>  J. Dai
>  Ph.D. Candidate,
>  Hefei National Laboratory For Physical Sciences at the Microscale,
>  University of Science and Technology of China,
>  Hefei, Anhui, 230026,
>  People's Republic of China
>  Tel.: 86-551-3606428
>  Fax.: 86-551-3602969
>  E-mail: jdai3 at mail.ustc.edu.cn
> =============================================================
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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
   v. Salaria Km 29,300 - C.P. 10                
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