[Pw_forum] Bi pseudopotential

[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