[Pw_forum] Bi pseudopotential

[Sven Heiles]

Hi Paolo, Emine!

Thanks for your reply tested your suggested US-PP which seem to work 
quite good.
Will have a look tomorrow on the performance for the dimer and the bulk.
Yesterday evening in a long night season I was able to find the problem 
with my
parameters and was able to fit a multiple projector, scalar relativistic 
NC-PP for LDA and PBE
functionals.

The performance of the PPs seem to be good (only judging on the geometrical
parameters; the electronic structure is a complete different topic of 
course)

Bi2 (bondlength):

PP-LDA  PP-PBE  PBE-Lanl2DZ    Exp [1]
2.57 AA     2.636 AA       2.64 AA     2.66 AA

Bi-A7 phase (see parameters in [2])

PP-LDA                PP-PBE               Theo[2]                Exp[2]
a0 = 4.573 AA     a0 = 4.766 AA      ao= 4.528 AA    ao= 4.726 AA
alpha = 58.271    alpha = 57.454     alpha = 58.93     alpha = 57.32
z = 0.237              z = 0.235               z =  0.238            z 
=  0.238

[1] Chem. Rev.  90 93 1990
[2] Phys. Scr. 37 785 1988

Thanks a lot again for your suggestions.

Best wishes

Sven

Am 10.03.2011 15:42, schrieb Sven Heiles:
> Dear QE users.
>
> Our group started to use QE and tries to combine the code with a global
> structural search routine. For this purpose
> valence only pseudopotentials (PP) optimized for a low energy cutoff has
> to be used (at the cost of computational correcetness of
> course). As a test case we want to start with Bi. For this element only
> a relatively hard PP exists which incoperates a d semicore
> state. Since the converted FHI PP 5-electron PPs does not work very well
> I decided to try to create a own PP.
>
> Have done the tutorial for Si and the example calculation for Ti and
> everything seemed to work all right. Because I am not very
> familiar with the theory of the PP fitting routines I tried to progress
> for Bi in the same manner as for Si and Ti. So I started with:
>
> &input
> iswitch=3, rlderiv=2.20, eminld=-2.0,emaxld=1.0,deld=0.01d0,nld=3,
> rel=1,zed=83.0,config="[Xe] 4f14 5d10 6s2 6p3 6d-1",dft='PBE',
> /
> &inputp
> lloc=2,pseudotype=1,file_pseudopw='Bi.pbe-n-rrkj.UPF', zval=5.0,rho0=0.01
> /
> 3
> 6S 1 0 2.00 0.00 2.20 2.20
> 6P 2 1 3.00 0.00 2.20 2.20
> 6D 3 2 0.00 -0.10 2.20 2.20
>
> But unfourtunately this input file produces the error "phi has nodes
> before r_c". Therefore
> tried to change rho0 , rcore and rcut systematically without success.
> Therefore used tm=.true.
> which produced a PP which looked good. Depressingly the TM potential
> failed to converge for
> test calculations for the dimer. Therefore changed the following things
> in the input:
> config="[Xe] 4f14 5d10 6s2 6p3", lloc=1, and got rid of the 6D in the PP
> card.
> In this way I am able to generate a PP. The wavefunctions and the logDev
> look ok. But the performance
> for the Dimer is not really good (40 Ry Ecutoff, RhoCutoff= 8*Ecutoff)
> ->  2.52 AA bondlength compared to
> 2.66 AA experimentally. For example a Lanl2DZ calculation in NWChem with
> the same functional yields
> 2.64 AA. Additionally any influence of the 6D state is not descibed with
> the potential.
>
> Every time I want to change the settings for the PP the program produces
> an error. I am not able so far to write
> in the 6D channel or in two channels (pseudotype=2) or to generate a
> US-PP (pseudotype=3).
>
> Since I am far away from beeing an expert and this are only my first
> attempts I wondered if someone has
> any suggestions what I could try to improve the PP for Bi step by step.
>
> Best wishes
>
> Sven
>


-- 
Dipl. Ing. Sven Heiles
Technische Universität Darmstadt
AK Schäfer
Eduard-Zintl-Institut
Petersenstraße 20
D-64287 Darmstadt – Germany

Phone: ++49-(0)6151-164397
Fax: ++49-(0)6151-166024
Web: http://www.tu-darmstadt.de/fb/ch/cluster/schaefer.tud