1 research outputs found
Correlation Energy Extrapolation by Many-Body Expansion
Accounting
for electron correlation is required for high accuracy
calculations of molecular energies. The full configuration interaction
(CI) approach can fully capture the electron correlation within a
given basis, but it does so at a computational expense that is impractical
for all but the smallest chemical systems. In this work, a new methodology
is presented to approximate configuration interaction calculations
at a reduced computational expense and memory requirement, namely,
the correlation energy extrapolation by many-body expansion (CEEMBE).
This method combines a MBE approximation of the CI energy with an
extrapolated correction obtained from CI calculations using subsets
of the virtual orbitals. The extrapolation approach is inspired by,
and analogous to, the method of correlation energy extrapolation by
intrinsic scaling. Benchmark calculations of the new method are performed
on diatomic fluorine and ozone. The method consistently achieves agreement
with CI calculations to within a few mhartree and often achieves agreement
to within ∼1 millihartree or less, while requiring significantly
less computational resources