The Morse Potential as a Bridge Between Molecular Structure and Dynamics

Abstract

CH bond lengths, HCH and HCC bond angles and CH symmetric and asymmetric stretching frequencies in alkane molecules are placed into four groups according to their occurrence in CH4,—CH3, 〉CH2 and–〉CH, and are seen to vary in a regular fashion. The physical rationale offered for these variations relates them to balanced interactions between adjacent orbitals of CH and CC bonds, which are assumed to be common to all energy surfaces of alkane molecules. Structural and dynamic observables are correlated by two Morse potentials, one for the CH bond and one for the CC bond. The stretching “force constants” thus become decreasing functions of bond length. The new force field reproduces the observed trend in bond lengths, bond angles and vibrational frequencies, mostly to within experimental accuracy.KeywordsBond LengthForce FieldVibrational FrequencyMorse PotentialMorse FunctionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.