EXTENSION OF MNDO TO D-ORBITALS - PARAMETERS AND RESULTS FOR THE HALOGENS

A recently proposed extension of the MNDO formalism to d orbitals has been parameterized for the halogens Cl, Br, and I. Extensive test calculations indicate slight consistent improvements for normalvalent molecules and dramatic improvements for hypervalent molecules, in comparison with established MNDO-type methods without d orbitals. The mean absolute errors in calculated heats of formation are 3.9 kcal/mol for 155 normalvalent compounds and 2.8 kcal/mol for 23 hypervalent compounds. The predicted structures of the hypervalent molecules are qualitatively correct, with a mean absolute error of 2-degrees in 19 bond angles.