Maybe somebody had this problem before. I am working on a system with two copper centers. THis system was found to be multireference in nature. I have already done some calculations and solution looks good that makes me happy. However, i need to expand my active space. I need to include some 3d-orbitals from coppers (they were not included before) and corresponding 3d' virtual orbitals to keep active space balanced. I started from CIS-NO. All 3d orbitals may be found easily. However, situation with virtual orbitals is not so simple. I may see some virtual orbitals of d-character but very delocalized over coppers and ligands. I also checked VVOs orbitals from GAMESS-US but it doesn't solve the problem. The worst thing is i need to include not all 3d orbitals but only xz,yz and z2 (square-planar copper(II)). How can i purify my virtual orbitals to make them more localized?
Thank you for any help.