The hydroxyl groups internal rotations in a methanediol molecule

Abstract

Internal rotation of two of hydroxyl groups in a methanediol molecule is analyzed by constructing the 2D surfaces of the potential energy, kinematic coefficients and dipole moment. The molecular characteristics in the nodes of 2D grids with different densities for distinct pairs of dihedral angles of OH groups were calculated at the MP2/cc-pVQZ level of theory with optimization of the geometry for all other structural parameters. For optimized at the MP2/cc-pVQZ level of theory geometries, the potential energy was additionally calculated at the MP2/cc-pVTZ level of theory in the same grid nodes and then the extrapolation of energies in every node to the complete basis set limit was performed. The kinematic parameters were calculated using the formalism of the Wilson vectors. The Hamiltonian matrix was compiled using the DVR method. As a result of its diagonalization, the wave functions and energies of stationary torsional states were determined. The calculated torsional wave functions were classified by irreducible representations of the C2V(M) molecular symmetry group. The frequencies and intensities of the torsional spectrum of a methanediol molecule were calculated at different temperatures for the trans- and cis-conformers. The tunneling frequencies for both conformers were calculated too.