Comment on: "Tunneling of coupled methyl quantum rotors in 4-methylpyridine: Single rotor potential versus coupling interaction". J. Chem. Phys. \textbf{147}, 194303 (2017)

Abstract

We analyze the results obtained recently by Khazael and Sebastiani (J. Chem. Phys. \textbf{147}, 194303 (2017)) for two coupled methyl rotors. We show that one of the avoided crossings obtained by those authors is in fact a true crossing between states of different symmetry. Present analysis is supposed to be clearer because it is based on an independent calculation of eigenvalues for each irreducible representation. The application of group theory also enables a more accurate calculation by means of smaller matrix representations of the Hamiltonian operator.