[Wien] Accuracy (relevance almost) of lstart energies

Laurence Marks L-marks at northwestern.edu
Tue Oct 16 14:21:21 CEST 2007

Thanks Peter.

That does leave open the related question of why for some atoms Wien2k
gives a lower total energy than lstart.....(with RELA).

On 10/16/07, Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote:
> lstart is "exact" (for good radial mesh and within a given DFT and for
> spherical atoms) !!! You cannot get a lower energy for a spherical atom
> in a given DFT functional.
> lstart is NOT a basisset method, but integrates the radial Schrödinger
> (in fact the dirac !) equation numerically. It finds the eigenvalues by the constraint
> that the solution at infinity must go to zero (normalization condition).
> It really is fully relativistic, therefore its energies are LOWER than
> WIEN2k-supercell energies and not compatible for the calculation of
> atomization energies.
> To test what I've said, you can switch off relativistic (NREL in case.struct)
> and then lstart and wien2k-supercells give (almost) the same energies.
> Laurence Marks schrieb:
> > I am curious about how good/useful are the energies in lstart. Of
> > course if one wants to calculate, for  instance, cohesion energies or
> > atomization energies one has to compare apples with apples, i.e. do a
> > Wien2k supercell calculation for a single atom. Ignoring this, how
> > "good" are the energies in lstart (assuming that one has an
> > appropriate NRAD etc)? Is the code using essentially the same method
> > as elsewhere in Wien2k but with subtle additions such as
> > orthogonalization of the levels? Is it technically better (or worse)?
> >
> > N.B., unfortunately the comments are in French, which I don't
> > understand as well as I probably should.
> >
> --
>                                        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/
> --------------------------------------------------------------------------
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Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
Web: www.numis.northwestern.edu
Commission on Electron Diffraction of IUCR

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