Scalable correlated electronic structure theory

The approach taken in Ames to advance high-level electronic structure theory has been a combination of the development and implementation of new and novel methods with the continuing development of strategies to optimize scalable computing. This work summarizes advances on both fronts. Several new methods have been implemented under the Distributed Data Interface (DDI), most recently including analytic Hessians for both Hatree- Fock and CASSCF (complete active space self-consistent field) wavefunctions, gradients for restricted open shell second order perturbation theory, and the fragment molecular orbital method (FMO). Exciting new method developments include the FMO method and the CEEIS (Correlation Energy Extrapolation by Intrinsic Scaling) method for efficiently approaching the exact energy for atomic and molecular systems.