APPROXIMATE AB-INITIO CALCULATIONS OF POLARIZABILITIES VIA THE EXCITATION SCHEME

The excitation scheme is explored as an alternative to the more usual coupled Hartree-Fock and similar analytical derivative calculations of polarizabilities and other molecular properties. The scheme can be im plemented more easily and requires only a small fraction of the comput er time and memory needed for conventional calculations. The accuracy of the two approaches is fully comparable for calculations done with i ncomplete basis sets. This is documented on computations of polarizabi lities and magnetic susceptibilities of water, pyridine and pyrimidine molecules performed at the HF and DFT (B3LYP) levels.