[Wien] Geometry optimization: constraint failed?

[Laurence Marks]

Setting a zero in case.inM only sets the gradient to zero, but you can
(do) have movement if the Hessian has non-zero cross-terms involving
this co-ordinate.

With 8.3 you need to run pairhess again AFTER editing case.inM, and
copy .minpair to .minrestart (and delete .min_hess if it is there).
This will remove the cross-terms in the Hessian.

Note: eigenhess in the latest version allows you to do this modifying
an existing .min_hess file which can be much faster.

On Fri, Oct 2, 2009 at 8:56 AM, Oleg Rubel <rubelo at tbh.net> wrote:
> Dear Wien2k Users and Developers,
>
> I calculate desorption of a dimer from a surface of III/V semiconductor using WIEN2k_08.3 (Release 18/9/2008). In this calculation, I would like to restrict the dimer from motion in Z direction perpendicular to the surface, though allow the atom to move in X-Y plane while searching for the lowest energy. To achieve this behaviour, I set up the *.inM file in the following way:
>
>    $ cat *.inM
>    PORT 2.0 0.35      # PORT/NEWT;  tolf, Initial Trust Radius
>    1.0 1.0 1.0 1.0   #Atom    1 Generated by pairhess
>    1.0 1.0 1.0 1.0   #Atom    2 Generated by pairhess
>    ...
>    1.0 1.0 0.0 1.0   #Atom  112 Generated by pairhess
>    ...
>
> Here atom 112 is one of two atoms in the dimer. But, after running "mini" I have got:
>
>    $ grep :POS112 *scf_mini
>    :POS112: AT.NR.-112 POSITION = 0.68430 0.32271 0.95580  MULTIPLICITY =  1
>    :POS112: AT.NR.-112 POSITION = 0.68654 0.32342 0.95523  MULTIPLICITY =  1
>    ...
>    :POS112: AT.NR.-112 POSITION = 0.71314 0.32367 0.95252  MULTIPLICITY =  1
>    ...
>    :POS112: AT.NR.-112 POSITION = 0.76567 0.32632 0.94984  MULTIPLICITY =  1
>
> Obviously, the Z coordinate changes during mini. My lattice is primitive:
>
>    $ cat *.struct
>    ...
>    P                          114 1 P1
>                 RELA
>     15.004806 30.009612 52.652500 90.000000 90.000000 90.000000
>    ...
>
> With this lattice size, the atom 112 was shifted in Z direction by 0.3 bohr during "mini"!
>
> My question is: Did I misinterpret the content of the *.inM file? How can I FIX Z coordinate and let X and Y to change?
>
> As a note: Setting "0.0 0.0 0.0 0.0   #Atom   63" does results in a desired behaviour when I want to fix atom 63 completely.
>
> Any suggestion are highly welcome.
>
> Thank you in advance,
>
> Oleg Rubel
>
> --
> Oleg Rubel, PhD
> Scientist
> Thunder Bay Regional Research Institute
> 290 Munro St
> Thunder Bay, ON
> P7A  7T1, Canada
> Phone: +1-807-7663350
> Fax: +1-807-3441948
> E-mail: rubelo at tbh.net
> Homepage: http://www.tbrri.com/~orubel/
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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.