Ab-initio calculations of small hydrides including electron correlation : II. Preliminary results for the CH4 ground state

The intrapair correlation energy of the CH4 molecule in its equilibrium configuraiton has been calculated by a method described previously by the authors. A value of -0.022 a.u. per CH-bond has been obtained, corresponding to a total energy of -40.312 a.u. The limit to be obtainable by taking into account the intrapair correlation only is estimated to be -40.385 +/- 0.01 a.u. which leads to an estimate of -0.017 a.u. for the interpair correlation energy between any two CH-bonds.