Diabatic CASSCF orbitals and wavefunctions

It is shown that diabatic CASSCF orbitals can conveniently be obtained via a block-diagonalization of the Fock matrix in a frozen-orbital representation. In a second step, diabatic N-electron wavefunctions are constructed by block-diagonalization of the Hamiltonian matrix in the representation of configuration-state functions. As a demonstration of the method, two-dimensional diabatic surfaces of the ¹A₂ and ¹B₁ excited states of ozone are reported.