The Role ofIntermolecular Interactions on the OpticalRotation of Chiral Systems in the Condensed Phase from Periodic CoupledCluster Simulations

Abstract In this study, we present an analysis of intermolecular interactions on the optical rotation (OR) of condensed phase systems. We investigate periodic 1D chains of H2O2 molecules and of a geometrically equivalent H4 model, and we determine the change in OR as a function of the intermolecular distance along well-defined molecular axes: the O–O bond axis, the C2 rotational axis, and a third axis perpendicular to the O–O bond and C2 axis. The simulations rely on the first implementation of the linear response function for the OR tensor at the coupled cluster level with single and double excitations with periodic boundary conditions (LR-CCSD-PBC), using the modified velocity gauge (MVG) and the origin-independent length gauge [LG(OI)] formalisms. We validate the methods against reference calculations on finite cluster chains aligned along the O–O bond axis, which allow us to explore the role of basis set size and k-point sampling of the first Brillouin zone in reciprocal space. Our results show that the effect of intermolecular interactions is significant even up to 8–10 Å between cells, which is likely an underestimation due to the compact basis set used in the simulations. Furthermore, simulations with point-charge embedding fail to reproduce both the quantitative and qualitative trends of the OR, indicating that the intermolecular effects are not due to polarization. Therefore, this study highlights that experimental observations of large OR changes passing from the gas to the condensed phase are due to long-ranged quantum mechanical effects.