Tools for analysing configuration interaction wavefunctions

P. Delaney, J. C. Greer

Research output: Journal PublicationConference articlepeer-review

1 Citation (Scopus)


The configuration interaction (CI) approach to quantum chemical calculations is a well-established means of calculating accurately the solution to the Schrödinger equation for many-electron systems. It represents the many-body electron wavefunction as a sum of spin-projected Slater determinants of orthogonal one-body spin-orbitals. The CI wavefunction becomes the exact solution of the Schrödinger equation as the length of the expansion becomes infinite, however, it is a difficult quantity to visualise and analyse for many-electron problems. We describe a method for efficiently calculating the spin-averaged one- and two-body reduced density matrices ρ Ψ(r̄;r̄) and Γ Ψ(r̄1,r̄2;r̄ 1,r̄2) of an arbitrary CI wavefunction Ψ. These low-dimensional functions are helpful tools for analysing many-body wavefunctions; we illustrate this for the case of the electron-electron cusp. From ρ and Γ one can calculate the matrix elements of any one- or two-body spin-free operator O. For example, if O is an applied electric field, this field can be included into the CI Hamiltonian and polarisation or gating effects may be studied for finite electron systems.

Original languageEnglish
Pages (from-to)240-249
Number of pages10
JournalComputational Materials Science
Issue number2
Publication statusPublished - Oct 2003
Externally publishedYes
EventProceedings of the Symposium on Software Development for Proce - Moscow, Russian Federation
Duration: 15 Sept 200216 Sept 2002

ASJC Scopus subject areas

  • Computer Science (all)
  • Chemistry (all)
  • Materials Science (all)
  • Mechanics of Materials
  • Physics and Astronomy (all)
  • Computational Mathematics


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