[Pw_forum] Ba ultrasoft psp

[Axel Kohlmeyer]

On Fri, 12 Jan 2007, Jess Kondor wrote:

JK>  Hello everyone,

jess,

JK>  Does anybody have a good Ba ultrasoft pseudopotential in LDA approximation?
JK> I generated one from vanderbilt library, but I feel did something wrong -

in case nobody responded yet and just as a caveat for everybody else. 
there is one thing that i noticed when re-creating pseudopotentials with 
the parameters from the vanderbilt library:

many of these parameter sets are rather old and it appears that the
polynomial fitting algorithm has been changed since, so that some
fine-tuning is required for heavier elements. you can tell from looking
at the output file from the pseudopotential generation, as it contains
warnings about negative densities. adding constraints to the polynomial
fitting to eliminate them or bring those as close to zero as possible
improves in my experience those potentials massively. without they 
seem ok in minimal tests, but as soon as you start looking at more
sensitive properties, the potentials start generating inconsistent
results.

JK> using it together with Ti and O from pwscf web-site on simple test I cannot
JK> get convergence more than 1.d-10 (moreover, on the last scf steps warning
JK> 'some eigenvalues do not converge' appears' - not a good sign according
JK> manual).

jess, if you're still interested, please let me know. it is 
rather straightforward to add a few constraints and redo the
potential. i can do this for you, if you would be willing to run 
a few tests (eg. lattice constant, bulk modulus etc.,) also for 
a couple other functionals, so that - if tested ok - they could
be added to the pseudopotential library...

cheers,
  axel.

JK> 
JK>  Regards,
JK>    JK
JK> 

-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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