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Valentin Monev
vmonev@orgchm.bas.bg

I have a (planar) molecule optimized at a high (mp2/ccpvtz+) level of theory, using C1 and Cs symmetry, i.e. two optimized geometries of the molecule, in the second of which the z coordinates are not 0.00xxx but pure 0.00000.

I know that using Cs symmetry the geometry optimizes in 7 points, while using C1 (no symmetry) takes 22 points! Delocalized coordinateds (dlc) are used in the optimizations, and "any DLCs will not be symmetry-preserving" http://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C34df668afbHW-7293-92+00.htm.

If I do a hessian calculation of these two optimized molecules, at C1(no symmetry) and Cs symmetry, will it take the same time, or will the Cs calculation be faster?

What do you think?

Valentin