I have performed a CASPT2 frequency calculation using the MOLCAS8 program package. I need the full Cartesian Hessian matrix as input for a subsequent program package.
MOLCAS8 performs CASPT2 frequency calculations numerically. The program
MCKINLEY is called for this purpose, however, it is now my opinion that all numerical second derivative calculations in MOLCAS are handled not by
MCKINLEY but by the barely documented module
supermac. Anyway, the Hessian is fully printed in internal coordinates once the calculation is finished. For a system of 10 atoms the internal Hessian is of size 24 x 24, which suggests non-redundant internal coordinates (MOLCAS calls them "primitive internal coordinates").
Does anyone know of a software capable of transforming a Hessian matrix from internal coordinates to Cartesian coordinates? I am aware that this will probably be complicated as internal coordinates are not as unambiguous and straight-forward as Cartesians. However, my initial search efforts did not yield a single software package capable of transforming a calculated Hessian in internal coordinates to Cartesians. Any help would be appreciated!
Alternatively, does someone know a quantum-chemical program package using which I might be able to obtain a full Cartesian hessian at CASPT2 level?
I don't know if this helps, but MOLCAS also seems to print out the force constants of each atom in Cartesian coordinates. Furthermore a
.molden file is produced where the normal modes are included. The full Hessian does not seem to be written to this Molden file though.