Beyond CCSD(T) Accuracy at Lower Scaling with Auxiliary Field Quantum Monte Carlo

We introduce a black-box auxiliary field quantum Monte
Carlo (AFQMC)
approach to perform highly accurate electronic structure calculations
using configuration interaction singles and doubles (CISD) trial states.
This method consistently provides more accurate energy estimates than
coupled cluster singles and doubles with perturbative triples (CCSD(T)),
often regarded as the gold standard in quantum chemistry. This level
of precision is achieved at a lower asymptotic computational cost,
scaling as O(N6) compared
to the O(N7) scaling
of CCSD(T). We provide numerical evidence supporting these findings
through results for challenging main group and transition metal-containing
molecules.