REPRESENTATION OF THE SPIN OPERATOR IN THE SPIN-FREE 2ND QUANTIZED APPROACH

This paper reports the representation of the spin operation <(S)(2)ove r cap>, corresponding to an N-electron system, using the spin-free sec ond quantization formalism. This approach allows to determine, in a su itable way, the S-representability of the second order reduced density matrix. A simple computational procedure for the construction of some basis functions of the irreducible representations of the symmetric g roup S-N, in terms of orthonormal spatial orbitals, is described. (C) 1998 Elsevier Science B.V.