## Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly

** Numerical gradients and CASSCF/XMQDPT2 **
Thomas

thomaspijper@hotmail.com

Dear Alex,I'm currently trying to do a XMQDPT2 numerical gradient calculation. Hereby, I have the problem that somewhere during the calculation of the gradient something goes wrong with the active space: the orbitals and state ordering after calculation of the gradient is completely different from those of the converged orbitals of the starting structure.

As I'm currently trying to find out what is going wrong, I would like to ask some more information about the initial guess that is used throughout the gradient calculation. Does each displacement start with the converged orbitals of the starting structure, or does each displacement use the converged orbitals of the previous displacement? If the latter is the case, how does this work together with the XP mode? And, at the end of a gradient calculation during a geometry optimization, which orbitals will be used as starting orbitals for the next geometry?

Also, is there a way to control this behavior?

Thanks in advance.

Kind regards,

Thom

*[ This message was edited on Fri Oct 5 '12 at 6:19pm by the author ]*

Fri Oct 5 '12 6:19pm

This message read **835** times