Using computed infrared intensities for fast computation of vibrational spectra

The Adaptive Vibrational Configuration Interaction (A-VCI) algorithm is an iterative pro-cess able to compute the spectrum of an Hamiltonian operator, using a discretization basisas small as possible. In this work, we show how this algorithm can handle more sophis-ticated operators, which ro-vibrational Coriolis coupling terms. In order to overcome theincrease of computing and storage resources needed due to this enrichment, the InfraRed(IR) intensities are computed and used as a criterion to select only the eigenstates corre-sponding to IR active vibrational states. The benefits of this new approach are presentedfor a few well studied molecular systems (H2O, H2CO, CH2NH, CH3CN, C2H4O), and itis ultimately applied to a 10-atom molecule (C4H4N2)