An ab initio study of the hydrogen-bonded H2O : HCN and HCN : H2O isomers

Ab initio calculations an performed on the hydrogen bond interaction betwee n HCN and water to analyze the structure, binding energy and change in vibr ational frequencies of the HCN:H2O isomer. After geometry optimization, sin gle-point calculations are made with many-body perturbation/coupled-cluster theories with different basis sets. At the highest level, CCSD(T), we find that the binding energy between HCN and water is 3.4 kcal/mol, after corre cting for the basis-set-super position error. Changes in intra-molecular vi brational frequencies are analyzed. (C) 2000 Elsevier Science B.V. All righ ts reserved.