Spin‐free quantum chemistry. XXIII. The generator‐state approach

AbstractIn the unitary‐group formulation of quantum chemistry, the spin‐projected, configuration‐state spaces of quantum chemistry are realized by the irreducible representation spaces (IRS) of the freeon unitary group U(n), where n is the number of freeon orbitals. The Pauli‐allowed IRS are labeled by the partitions [λ] = [2(N/2)−s, 12S], where N and S are the particle number and the spin, respectively. The generator‐state approach (GSA) to the unitary‐group formulation consists of (1) the construction of the overcomplete, nonorthonormal generator basis for each IRS; (2) the Lie‐algebraic computation of matrix elements over generator states; (3) the Moshinsky–Nagel construction of the complete, orthonormal Gel'fand basis in terms of the generator basis; and (4) the computation of matrix elements over Gel'fand states in terms of matrix elements over generator states.