[Pw_forum] fully relativistic pseudopotential for Co

[Axel Kohlmeyer]

On Wed, 2009-04-22 at 07:21 -0700, Álvaro Alves wrote:


> 
> Hi all. I build a fully relativistic pseudopotencial for cobalt. When
> testing it I found the following results for lattice parameters: a =
> 2.44 A, c = 4.03 A and c / a = 1.65. The experimental values are 2.51
> A, 4.07 A and 1.62.  I want to improve these results. Do you have any
> suggestions? My input is below.
> 

alvaro,

you can try sacrificing five chickens or a goat, bow five times to mecca
or pray 5 ave marias.

other than that, i'd say that you have a less than 3% overbinding for
the lattice parameter
and 1% deviation in c and and since both errors are towards the same
direction you have
an error of 2% in c/a. to the best of my knowledge, this is pretty much
of what people report 
as typical error margins for a gradient corrected functional, only that
i remember seeing
underbinding more commonly than overbinding (the latter would be more
common in LDA).

at this point, the black magic of pseudopotential generation begins. you
can twiddle with
cutoffs and electron configuration and see if this shifts the results
closer to what you want,
while not harming transferability (how transferable is this potential
anyways? did you test it?).

cheers,
   axel.

-- 
=======================================================================
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
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.
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