Configuration Interaction

In this section configuration interaction methods will be described.

CI Singles

The CI singles are done by building a Hamiltonian and diagonalizing it. The Hamiltonian build accourding to:

\[H_{ia,jb} =f_{ab}\delta_{ij}-f_{ij}\delta_{ab}+\left\langle aj\left|\right|ib\right\rangle\]

Here everything is in spin orbital basis.

FUNCTION:

  • CI.CIS(occ, F, C, VeeMOspin)
  • return Exc

Input:

  • occ, number of occupied MOs in spinbasis
  • F, fock matrix in spatial basis
  • C, MO coeffcients in spatial basis
  • VeeMOspin, MO integrals in spin basis

Output:

  • Exc, single excitation energies

References: