Chemical Physics Letters
Ab initio calculations on CH4 → CH3 + H were performed at the MP4/6-31G** level including all single, double triple and quadruple excitations. Although triple excitations have little effect on the dissociation energy, they are very important in the 2–3 Å range. The potential curve appears to rise more sharply than a Morse curve in this region. Correlation effects are not important for the HCH angle optimization.
Ronald J. Duchovic, W L. Hase, H B. Schlegel, M J. Frisch, and K Raghavachari (1982).
Ab Initio Potential Energy Curve for CH Bond Dissociation in Methane. Chemical Physics Letters.89 (2), 120-125.