This work presents a novel method for the calculation of non-covalent interactions in intermolecular complexes. A linear scaling Fock build utilising absolutely localised molecular orbitals (ALMOs) results in exclusion of basis set superposition errors (BSSE). The correlation treatment is based on a new pairwise local random phase approximation, and a bespoke data structure along with density fitting ensure linear scaling in the storage and computation of two-electron integrals. Results reach a similar accuracy as CCSD, yet a large cluster of water molecules (over 3500 basis functions) can be computed in less than 10 minutes on a single desktop processor.
An open-source program (GAMMA) based on this work is under development.
A linear-scaling method for non-covalent interactions: An efficient combination of absolutely localized molecular orbitals and a local random phase approximation approach. R. A. Shaw and J. G. Hill, J. Chem. Theory Comput., 2019, 15, 5352.