(Complete Neglect of Differential Overlap) The simplest of the semi-empirical methods. The principle feature is the total neglect of overlap between different orbitals. In other words, the overlap matrix S is the unit matrix. The only two-electron integrals kept are those where electron 1 is in just one orbital and electron 2 is in just one orbital. Like all semiempirical methods the integrals are evaluated empirically.