Extending Atom-Atom Polarizabilities to Frequency-Dependent Coupled Cluster and MCSCF Response

The methodology for calculating distributed atom-atom polarizabilities within the minimal basis iterative Stockholder partitioning framework is extended to coupled cluster (CC2, CCSD, CC3) and multiconfigurational self-consistent field (MCSCF) wave functions, as well as to frequency-dependent perturbations. The bond capacity, defined as the rank-0 atom-atom polarizability, is benchmarked on small molecules at equilibrium geometries, where various DFT functionals show good agreement with the CC3 reference. The same conclusion holds when probing geometry dependence through a change in the bond angle or dihedral angle, but a significant deviation is observed between the methods for reaction pathways such as SN2. The MCSCF implementation is used to study the values for bond breaking, where the rank-0 contribution to the molecular dipole polarizability is found to dominate for various systems. Non-nuclear sites for describing out-of-plane polarizability at the charge-only level are also explored but found to be ineffective with ab initio-derived parameters. Dynamic bond capacities at real and imaginary frequencies are presented and display method dependence consistent with that of the static values.