Novel Truncated and Stochastic Approaches to Configuration Interaction

We review non-traditional approaches to configuration interaction including novel ways to truncate the configurationinteraction wavefunction using perturbation, a priori selection andMonte Carlo procedures. Calculations of the full configuration interaction wavefunction using projector or diffusion Monte Carlo methods are also discussed. The authors’ results using Monte Carlo configuration interaction for potential curves and non-variational quantities (multipole moments) are presented. The use of approximate natural orbitals to accelerate a Monte Carlo configuration interaction calculation is also investigated.