PC GAMESS/Firefly-related discussion club

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Damodaran Krishnan
damodak@pitt.edu

X-ray structures generally does not have hydrogen coordinates, hence I add H atoms to the structure and do a constrained optimization (i.e. optimize the H atom positions keeping heavy atoms fixed). This is easy to do with G03 since it lets me freeze XYZ coordinates of any atom. But I am a PCGAMESS/Firefly fan and also this is much faster, so could somebody suggest an easy way to fix coordinates of all heavy atoms and optimize all H atom positions using Firefly.

Firefly manual says “You cannot freeze Cartesian cords”

Thanks very much.