Use of promolecular ASA density functions as a general algorithm to obtain starting MO in SCF calculations

Abstract

Atomic shell approximation (ASA) constitutes a way to fit first-order density functions to a linear combination of spherical functions. The ASA fitting method makes use of positive definite expansion coefficients to ensure appropriate probability distribution features. The ASA electron density is sufficiently accurate for the practical implementation of quantum similarity measures, as was proved in previous published work. Here, a new application of the ASA density formalism is analyzed, and employed to obtain an initial guess of the density matrix for SCF procedures. The number of cycles needed to assess the convergence criterion in electronic energy calculations appears comparable to or less than those obtained by other means. Several molecular structures of different classes, including organic systems and metal complexes, were chosen as representative test cases. In addition, an ASA basis set for atoms Sc-Kr fitted to an ab initio 6-311G basis set is also presented.

Atomic effective potentials for starting molecular electronic structure calculations

“…A linearized version thereof is simply the sum of fixed neutral-atom potentials taken from a density-functional calculation, which, remarkably, has been introduced and benchmarked for the first time only a few months ago [12]. There is also a Hartree-Fock analog [13] that needs up to three-center two-electron integrals, or its spherical approximation [14] with less costly models of the direct and exchange terms.…”

Study of interaction energies between residues of the active site of Hsp90 and geldanamycin analogues using quantum mechanics/molecular mechanics methods

“…In contrast, this common recognition of substructures produces a coherent alignment with chemical intuition. TGSA-Flex program was used to perform this procedure because is simple and has low computational requirements [32][33][34][35][36] .…”

Improvement of initial guess via grid‐cutting for efficient grid‐based density functional calculations

“…In contrast, the former can express wave functions for any type of external potential including the nuclear potential of molecular systems as long as sufficient number of grid points is used. Despite of their different natures, available grid‐based methods rely on initial guess methods which are commonly used in atom‐centered basis sets; for example, core Hamiltonian method, extended Hückel (EH), superposition of atomic densities (SAD), linear combination of atomic orbitals (LCAO), and others …”