A COMPUTATIONAL EVALUATION OF THE STRUCTURE AND HEAT OF FORMATION FORFOCL AND CL2O

The structure of FOCl and Cl2O have been investigated using state-of-t he-art ab initio methods. Electron correlation methods that have been used are second-order Moller-Plesset perturbation theory, configuratio n interaction with single and double excitations (CISD), singles and d oubles coupled-cluster theory (CCSD), and quadratic configuration inte raction with single and double excitation along with perturbative corr ections for triple excitation (QCISD(T)). The equilibrium structure ha s been determined for FOCl and Cl2O. The heat of formation for Cl2O is estimated as 19.3 +/- 2 kcal mol-1 and compares well with the experim ental determinations; for FOCl it is 13.4 +/- 2 kcal mol-1 at 298 K. T here is a major discrepancy between the theoretical estimate of the he at of formation of FOCl and that determined experimentally from electr on-impact/mass spectrometry.