Finite-Difference and Analytic-Gradient Approaches for Simulating Vibrational Circular Dichroism Using Second-Order Møller-Plesset Perturbation Theory and Configuration Interaction

Abstract

Vibrational circular dichroism (VCD) is defined as the differential absorption of left- and right-circularly polarized light in the infrared region of the electromagnetic spectrum. Application of this spectroscopy is primarily directed towards the elucidation of molecular absolute configuration. As a result of the complex relationships involved in light-matter interactions, theoretical simulation is required to interpret experimental results. In this work, we focus on improving the accuracy and efficiency of simulating VCD spectra. First, we discuss the effects of the choice of basis set on two chiroptical properties including VCD and Raman optical activity (ROA) with a particular emphasis on property-oriented basis sets. Next, we introduce a finite-difference scheme for computing the atomic axial tensor (AAT), a required quantity for VCD simulation, for the second-order Møller-Plesset perturbation (MP2) theory and configuration interaction with double excitations (CID) electronic structure methods. Finally, we formulate an analytic implementation of the MP2 and configuration interaction including single and double excitations (CISD) AATs.