Hi,

Concerning crystal-field-cons= trained optimization you can try to use the QM/MM method. I have used it fo= r the calculation of excited states in molecular crystals and it works very= well. You can check it out in: R. Kaminski. M. S. Schmokel, P. Coppens, J.= Phys. Chem. Lett., 2010, 1, 2349. The reprint is on my web-site: http://www.chem.uw.edu.pl/people/RKaminski/publicat= ions.html
=0A
Cheers,

Radek

2011/3/13 Rajagopala Reddy Seelam rajagopalaseelam]~[<= a rel=3D"nofollow" target=3D"_blank" href=3D"http://gmail.com">gmail.com <owner-chemistry*ccl.net>
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=0ASent to CCL by: "Rajag= opala Reddy Seelam" [rajagopalaseelam]*[gmail.com]
=0AHello CCL subscribers,=0AI have xyz coordinates of a crystal structure solved from X-Ray Diffrac= tion Studies. I want to calculate excited states of this molecule using g03= . Please answer me following few queries.
=0A
=0A1) I am in confusion= in deciding to go for either a single point
=0A energy calculati= on or an optimization. If I optimize the geometry,
=0A the result= ing geometry is not as same as the structure obtained
=0A from cr= ystal structure. Rather it will be isomer for the crystal
=0A str= ucture. Which is the best way to proceed for crystal structure ?
=0A
= =0A2) I am getting imaginary frequencies for this structure at single
= =0A point energy. In principle we should not get any imaginary frequ= encies
=0A for stable molecule. What is workaround for this probl= em.
=0A
=0AThank you so much
=0Abest wishes
=0ARajagopala Reddy= Seelam
=0A
=0A
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--
Radoslaw Kaminski, = M.Sc. Eng.
Ph.D. Student
Crystallochemistry Laboratory
Department = of Chemistry
University of Warsaw
Pasteura 1, 02-093 Warszawa, Poland=
=0Ahttp://www.chem.uw.edu.pl/people/RKaminski/
= =0A