Posted by Björn Roos on February 14, 2006 at 10:43:27:
In Reply to: Can force constants be comoputed at CASPT2+SOC level? posted by Wenli Zou on February 14, 2006 at 04:21:58:
: It seems not (I'm not sure). However, in the paper Gagliardi, Roos, Malmqvist, and Dyke, On the Electronic Structure of the UO2 Molecule, J. Phys. Chem. A 2001, 105, 10602, the frequencies derived from force constants at CASPT2+SOC level are listed.
: Could you confirm this?
Force constants at the CASPT2-SOC level were computed numerically. An energy surface was fitted to a second order polynomial. This is no problem for a three-atom system at any level of theory. For a molecule with N atoms one need to compute (N+1)(N+2)/2 energy points to create such a surface. It has been done for excited states of pyrrol with 9 atoms without problems.