Molecular gradients for semiempirical CI wavefunctions with floating occupation molecular orbitals

Configuration interaction based on floating occupation Hartree-Fock molecul ar orbitals has proved to be an useful tool in the study of photochemical r eactions. In this paper we describe a method for the calculation of the mol ecular energy gradient of a CI type wavefunction built with orbitals obtain ed from a semiempirical Hartree-Fock calculation using floating occupation numbers with gaussian broadening. Our method is tested by computing Potenti al energy curves for the acetone photodissociation reaction. (C) 2000 Publi shed by Elsevier Science B.V.