An ab initio calculation of the potential for the interaction of a hydrogen atom with an ethane molecule

In this paper ab initio methods including PMP2/aug-cc-pVTZ, CCSD(T)/6-311++G(d,p), and G2 methods are used to calculate the interaction potential for a hydrogen atom approaching ethane along the carbon-carbon axis of ethane. The potential shows a shallow minimum at about 4.0 Angstrom and a strong repulsive core. The position of the minimum moves to smaller distances as the size of the basis set increases. Concurrently, the strength of the core repulsion decreases and the well depth increases. PMP2 calculations show a slightly shallower well than do CCSD(T) calculations, but the repulsive potentials are virtually identical. The potential is well represented by a Morse potential. An exponential-6 potential, a simple exponential, an anti-Morse potential or a Kihara potential fit the data less well. A Lennard-Jones potential and a Mie potential show substantial deviations. A new exponentially damped exponential-6 potential fits the repulsive region slightly better than the Morse exponential-ti, anti-Morse, and Lennard-Jones potentials. Potential parameters are included in the paper.