PC GAMESS/Firefly-related discussion club

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Alex Granovsky
gran@classic.chem.msu.su

this type of analysis is not explicitly implemented in Firefly
at present. On of the reasons is that in the most cases, an overhead
due to calculation of the full Hessian matrix is quite acceptable,
especially for the semi-numerical calculations. However, it is still
possible to perform PHVA - the simplest way is just to assign
very large masses (e.g. 10⁶) to the atoms you'd like
to fix.

Hope this helps.

Regards,
Alex Granovsky




On Sat Oct 31 '09 4:45pm, Dmitry Ryndyk wrote
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>Is it possible to use PC GAMESS/Firefly for constrained vibrational analysis, when some coordinates are fixed? It is also known as the partial Hessian vibrational analysis (PHVA), in which only a subblock of the Hesssian matrix is diagonalized to yield vibrational frequencies. Of cause, if the full Hessian matrix is known, it is easy to do PHVA, but it is very time-consuming to calculate the elements, which are not used.