Efficient and automated quantum chemical calculation of rovibrational nonresonant Raman spectra

An outline of a newly developed program for the simulation of rovibrational nonresonant Raman spectra is presented. This program is an extension of our recently developed code for rovibrational infrared spectra [Erfort et al., J. Chem Phys. 152, 244104 (2020)] and relies on vibrational wavefunctions from variational configuration interaction theory to allow for an almost fully automated calculation of such spectra in a pure ab initio fashion. Due to efficient contraction schemes, this program requires modest computational resources, and it can be controlled by only a few lines of input. As the required polarizability surfaces are also computed in an automated fashion, this implementation enables the routine application to small molecules. For demonstrating its capabilities, benchmark calculations for water H₂ ¹⁶O are compared to reference data, and spectra for the beryllium dihydride dimer, Be₂H₄ (D_2h), are predicted. The inversion symmetry of the D_2h systems lead to complementary infrared and Raman spectra, which are both needed for a comprehensive investigation of this system.