[Pw_forum] questions about the peseudopotential for potassium titanate

[Axel Kohlmeyer]

On Tue, 2009-03-24 at 05:05 +0100, Stefano de Gironcoli wrote:
> Dear Vega,
> 
> 
>    THe pseudo K.pz-sp-van.UPF has been generated with the vanderbilt  
> code. you   can
> likely find the corresponding input in the Vanderbilt website.
>    It should be easy to modify it by replacing the LDA PZ functional with pw91.

stefano,

unfortunately, it is not that easy. the vdb atomic code requires a
different polynomial fitting procedure for GGAs than for LDA. one has
to tweak the input a little bit more and most of the time, also include
some additional constraints to avoid unphysical negative densities as a
result of the different fitting. once you have one GGA functional, you
can usually regenerate all of them with the same parameters, as well as
an LDA potential.

cheers,
   axel.

>    don't forget to test the new pseudo in some simple system before  
> trusting it.
>    hope this helps,
>    stefano
> -
> Stefano de Gironcoli -SISSA and DEMOCRITOS
> 
> 
> Quoting vega lew <quantumdft at gmail.com>:
> 
> > Dear all
> >
> > I want the calculate the properties of potassium titanate. And I want to use
> > the pw91 functionals for the whole caculation. But I find the
> > peseudopotential for K is something different with the Ti and O. From the
> > name of pp, we could see functionals for K is different from Ti and O. Do
> > you think I could use
> > K.pz-sp-van.UPF<http://www.quantum-espresso.org/pseudo/1.3/UPF/K.pz-sp-van.UPF>with
> > the O.pw91-van_ak.UPF and Ti.pw91-sp-van_ak.UPF to describe the
> > potassium titanate. Actually I want to use pw91 functionals for the
> > calculation. How could I deal with the K+?
> >
> > thank you for reading
> >
> > any hints will be deeply appreciated
> >
> > vega
> >
> >
> > --
> > ==================================================================================
> > Vega Lew ( weijia liu)
> > PH.D Candidate in Chemical Engineering
> > State Key Laboratory of Materials-oriented Chemical Engineering
> > College of Chemistry and Chemical Engineering
> > Nanjing University of Technology, 210009, Nanjing, Jiangsu, China
> > ******************************************************************************************************************
> > Email: vegalew at gmail.com
> > Office: Room A705, Technical Innovation Building, Xinmofan Road 5#, Nanjing,
> > Jiangsu, China
> > ******************************************************************************************************************
> >
> 
> 
> 
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-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
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