| Abstract: | A direct, matrix-oriented procedure in the context of the self-consistent electron pairs (SCEP) method has been implemented for the evaluation of first derivatives of the energy of a variational configuration interaction wavefunction. This has been applied in calculating dipole and quadrupole moments of the correlated charge distributions of several small molecules. As already established, the analytical differentiation being carried out yields properties slightly different than those calculated by integration with the one-electron density. The matrix-oriented analytical differentiation is computationally competitive with construction of the one-electron density. |
