[molpro-user] How to do the double d-shell casscf calculation ??

[章晓斌]

Dear Molpor Users,

I want to do some casscf calculations for nickel oxides.I know that 
transition metal chemistry (1st row) sometimes requires a double d-
shell descriptionin the active space.

The question is that：
Should I include the 4d orbital or just use more diffuse basis set? 

For example, in article the author says that：

"To model correlation in the d shell and to include the double-shell 
effect, all occupied Fe 3d orbitals (72a, 73a and 45b) were correlated
by 4d orbitals (76a, 77a and 46b)and the bonding orbitals were descr-
ibed with antibonding correlating orbitals."

And how to add the 4d orbital?

Best regards, 
Xiaobin Zhang