Advertisement

On the implicit integral character of Roothaan's expansion

  • H.F.M. DaCosta
  • M. Trsic
  • A.B.F. da Silva
  • A.M. Simas

Abstract:

The molecular generator coordinate Hartree-Fock method is reviewed. The connection between a quadrature solution of the generator coordinate Hartree-Fock equations and Roothaan's equations is stressed. The relation between linear expansion coefficients and generator coordinate weight functions is discussed and a numerical and analytical example is provided for the 1s orbital of the hydrogen atom represented as the integral transform of a Gaussian function. For the same example, the Gauss-Labatto quadrature is employed to emphasize the implicit integral character of Roothaan's equations. As a major conclusion, the interpretation that every LCAO calculation is actually performing integrations of the Griffin-Wheeler equations is advanced. Basis sets are therefore abscissas of the implicit quadrature used in the integration, whereas the linear coefficients automatically incorporate the corresponding weights. Subsequently, it is shown how to extract the generator coordinate weight function from the LCAO coefficients which has the advantage of being a characteristic of the physical system under study and not of the particular calculation being carried out. As such, basis set design becomes how to efficiently sample the weight function.

PACS. 31.15.Ar Ab initio calculations 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© EDP Sciences, Springer-Verlag 1999

Authors and Affiliations

  • H.F.M. DaCosta
    • 1
  • M. Trsic
    • 1
  • A.B.F. da Silva
    • 1
  • A.M. Simas
    • 2
  1. 1.Departamento de Química e Física Molecular, Instituto de Química de S ao Carlos, Universidade de S ao Paulo, P.O. Box 780, 13560-250, S ao Carlos, SP, BrasilBR
  2. 2.Departamento de Química Fundamental, Universidade Federal de Pernambuco, 50670-901, Recife, PE, BrasilBR

Personalised recommendations