[Wien] Force calculations: a problem with Bi

[Laurence Marks]

Which version of Wien2k? Centro-symmetric or not? How big is the
discontinuity at the RMT, and how large are the distances between the
atoms (if too small there can be problems)? What are the RMT's (maybe
attach the struct file, as well as in1/in2.

On Wed, Feb 17, 2010 at 12:36 PM, mazin <mazin at nrl.navy.mil> wrote:
> I am calculating a Bi-containing compound, BiOCuS. It has a rather simple
> tetragonal structure with two free parameters, Bi (z) and S (z).
>
> When I vary Bi(z) keeping everything else fixed I obtain a well defined
> total energy minimum at one z, and a well defined Bu force zero at another
> z. Both sets of calculations are well converged, k-mesh convergence, RKmax,
> GKmax, fft, linearization parameters, rMT dependences etc are all tested.
> Including more semicores states does not affect the results either. A closer
> inspection shows that the force obtain by taking the derivative of the total
> energy agrees well with the calculated forces, if the latter are shifted by
> 63 mRy/bohr (a huge number). The calculations are nonmagnetic and scalar
> relativistic.
>
> I vaguely remember having some problems quite some time ago with force
> calculations for another Bi compound, but at that time I never got to the
> bottom of that.
>
> I wonder if this is a known problem and if anybody stumbled upon it before.
>
> I.M.
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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
Chair, Commission on Electron Crystallography of IUCR
www.numis.northwestern.edu/
Electron crystallography is the branch of science that uses electron
scattering and imaging to study the structure of matter.