Benchmarking distinguishable cluster methods to platinum standard CCSDT(Q) non-covalent interaction energies in the A24 dataset.

Recent disagreement between state-of-the-art quantum chemical methods, coupled cluster with single, double, and perturbative triples excitations and fixed-node diffusion Monte Carlo, calls for a systematic examination of possible sources of error within both methodological approaches. Coupled cluster (CC) theory is systematically improvable toward the exact solution of the Schrödinger equation; however, it is very quickly limited by the computational cost of the calculation. Therefore, it has become imperative to develop low-cost methods that are able to reproduce CC results beyond the CC theory with single, double, and perturbative triples [CCSD(T)] level of theory. Here, the distinguishable cluster (DC)-CCSDT and singular value decomposed (SVD)-DC-CCSDT methods are examined for their fidelity to the CCSDT(Q) correlation interaction energies for the A24 dataset and are shown to outperform CCSDT and CCSD(T). Furthermore, with (T)-based corrections of the SVD approximation, the SVD-DC-CCSDT method becomes an accurate and relatively low-cost tool for the calculation of previously intractable post-CCSD(T) energies in atomic orbital basis sets of unprecedented size.