Generalized linear-scaling localized-density-matrix method

A generalized linear scaling localized-density-matrix (LDM) method is devel oped to adopt the nonorthonormal basis set and retain full Coulomb differen tial overlap integrals. To examine its validity, the method is employed to evaluate the absorption spectra of polyacetylene oligomers containing up to 500 carbon atoms. The semiempirical Hamiltonian for the pi electrons inclu des explicitly the overlap integrals among the pi orbitals, and is determin ed from the ab initio Hartree-Fock reduced single-electron density matrix. Implementation of the generalized LDM method at the ab initio molecular orb ital calculation level is discussed. (C) 1999 American Institute of Physics . [S00219606(99)31104-1].