[Wien] What is U(R) in potential parameters (case.output1, SRC_lapw1/atpar.f P(J, JATOM))

[Peter Blaha]

If you consider, how the LAPW-matrix elements are formed (see eg. 
J.Phys.F: Melal.Phys. 5, 2041 (1975)), you see that basically only the 
value of the radial wavefunctions at R=RMT enter. Thus the quantities

     U(R)          U'(R)         DU/DE        DU'/DE      NORM-U'

are U: radial wave function (actually it is R(r).r) at RMT
     U':  dU/dr
     DU/DE:  = u-dot = energy derivative
     DU`/DE:     energy derivative of U'

With these numbers the Hamilton and overlap matrix elements are formed.

It was well known in the original APW method, where the logarithmic 
derivative entered the matrix elements and (u/u') could become infinity, 
that sometimes the secural equation became singular.
LAPW has removed this problem (there is no division anymore), but I 
don't know if it might happen that when u (or one of the other 
parameter) is (nearly) zero, two rows of matrixelements become very 
similar leading to Cholesky-problems.

Did you find any difference between APW+lo+LO and LAPW+LO (0 or 1 in 
case.in1) ?

You think you always get problems connected with LOs ?
It that always for MgO systems ?

Are the two energies E1 and E2 for the energy parameters different enough ?

PS: I had funny errors during Christmas: On two of our new Core2 
machines I got a Cholesky error when both processors where used by two 
jobs. However, when I repeat the lapw1 run the error did NOT show up 
anymore (No change, simply rerunning !!!). I did not find that when 
using only one processor and it occurred just a few times.

Regards

Laurence Marks schrieb:
> Does anyone know what exactly U(R) in the potential parameters printed
> in case.output1 by SRC_lapw1/atpar.f is, stored in the array
> P(J,JATOM)? I've traced that when this gets small both B and C in the
> APW+lo expansion get small, you can get a Cholesky factorization error
> and also the forces can get inaccurate. Unfortunately my German is non
> existent.
> 

-- 

                                       P.Blaha
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: 
http://info.tuwien.ac.at/theochem/
--------------------------------------------------------------------------