Fingerprint region of the formic acid dimer: variational vibrational computations in curvilinear coordinates

Abstract

Curvilinear kinetic energy models are developed for variational nuclear motion computations including the inter- and the low-frequency intra-molecular degrees of freedom of the formic acid dimer. The coupling of the inter- and intra-molecular modes is studied by solving the vibrational Schrödinger equation for a series of vibrational models, from two up to ten active vibrational degrees of freedom by selecting various combinations of active modes and constrained coordinate values. Vibrational states, nodal assignment, and infrared vibrational intensity information is computed using the the full-dimensional potential energy surface (PES) and electric dipole moment surface developed by Qu and Bowman [Phys. Chem. Chem. Phys. 18, 24835 (2016); J. Chem. Phys. 148, 241713 (2018)]. Good results are obtained for several fundamental and combination bands in comparison with with jet-cooled vibrational spectroscopy experiments, but the description of the ${\nu }_8$ and ${\nu }_9$ fundamental vibrations, which are close in energy and have the same symmetry, appears to be problematic. For further progress in comparison with experiment, the potential energy surface, and in particular, its multi-dimensional couplings representation, requires further improvement.

References in corpus (2)

• Towards breaking the curse of dimensionality in (ro)vibrational computations of molecular systems with multiple large-amplitude motions
• Rovibrational quantum dynamical computations for deuterated isotopologues of the methane-water dimer

Cited by in corpus (6)

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• Transfer Learned Potential Energy Surfaces: Accurate Anharmonic Vibrational Dynamics and Dissociation Energies for the Formic Acid Monomer and Dimer
• Methane dimer rovibrational states and Raman transition moments