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278. SPUHF: Brickstock-Pople UHF Calculation with
Harriman Spin Projection Treatment
by J. C. Schug, D. H. Phillips, and D. A. Brewer, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 This program performs an unrestricted Hartree-Fock calculation on a planar pi-electron system using PPP approximations. The first atom is located at the origin. Other atoms are positioned by using plane polar coordinates with an origin on any previously located atom.The program transforms these to Cartesian coordinates and calculates electron repulsion integrals using the selected method. The off-diagonal core Hamiltonian matrix elements are read in as data. Initial orbitals are estimated by a Hückel calculation. Iterative SCF calculations are then carried out until the energy is consistent to 10-6 eV or until the desired maximum number of iterations have been carried out. There is an option to employ a non-Aufbau approximation for the density matrix at the first iteration if this is desired. Subroutine WATE performs spin projections for the desired number of spin states, using the equations of Harriman and coworkers. For each spin state, the program calculates the energy of the projected state, the charge density matrix, the diagonal elements of the two-particle charge density matrix, and the projected spin densities. FORTRAN IV (IBM 360/370) Lines of Code: 1272 Recommended Citation: J. C. Schug et al., QCPE 11, 278 (1975). |