DOES THE METHYL-GROUP FORM A HYDROGEN-BOND - AB-INITIO POST-HARTREE-FOCK STUDY ON ETHANE-HYDROGEN CYANIDE COMPLEX

Ab initio LCAO-MO methods at the second-and fourth-order Moller-Plesse t levels and coupled cluster CCSD and CCSD(T) approximations have been applied to investigate a formation of a hydrogen bond by a methyl gro up in the ethane-hydrogen cyanide complex. Geometrical parameters obta ined from an MP2/6-311 ++ G* optimization are reported. The optimized geometry characterizes a minimum energy structure, Stability of the c omplex is evaluated using both the supermolecular counterpoise approac h and the symmetry-adapted perturbation theory. The depth of the minim um is about 0.6 kcal/mol. Thus, one may consider this dimer as an exam ple of a very weak hydrogen-bonded system. (C) 1998 Published by Elsev ier Science B.V.