[Wien] AIM: Laplacian ?

[Peter Blaha]

> Thank you very much for your help. I assume this is the laplacian of the
> valence density only (case.clmVAL) ? And if so, is it possible to obatin the
> full-electron laplacian as well ?

No. When you use lapw0 it calculates the laplacian from the all-electron
density.
However, when you plot it using lapw5, the program lapw5 "expects" a file
called case.clmval. So you should copy the "rsp" file to case.clmval.

> I am insterested in the topology of the Laplacian and in ELF as well. Is this
> somehow already implemented in WIEN, or is there any other program available
> to obtain the ELF from a WIEN calculation ?

I know that somebody is working on it, but have no details. I would guess
it should be simple to get ELF once one has the laplacian.

> One last question: As the wavefunction is fittet to be continuous in it's
> value and slope at the edge of the MT there still might be a non-continuous
> behaviour in the second derivative - which would also be "transferred" to the
> density's second derivative. As far as I can see there is no way to avoid
> this problem as you can only use two constrains when solving the
> Schroedinger-Equation inside the spheres. Is there a possibility to avoid
> these possible artifacts in the Laplacian/ELF ?

I do not have much experience with the Laplacian. However, I have a little
experience with Baders aim method. While it is true that the BASISFUNCTIONS
are continuous only in first derivative (not even this when using APW+lo),
I'm not so sure if this is the real problem, since the variational total
wavefunctions might be ok. On the other hand much more serious problems are
caused by two further approximations:
i) The core density is cut-off at RMT. So make sure that you have a really
   small core. I have seen small discontinuities even for C-1s. To fix this
   would require to superpose the full core densities (as done in dstart with
   the atomic densities at the beginning.
ii) The LM-representation of the density is by default truncated at L=6.
   Go further up to L=10 by manually inserting proper LM combinations into
   case.in2

Regards

                                      P.Blaha
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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/
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