Atomic Partitioning of the MPn (n=2,3,4) Dynamic Electron Correlation Energy by the Interacting Quantum Atoms (IQA) Method: a Fast and Accurate Electrostatic Potential Integral Approach

Recently the quantum topological energy partitioning method called Interacting Quantum Atoms (IQA) has been extended to MPn (n=2,3,4) wavefunctions. This enables the extraction of chemical insight related to dynamic electron correlation. The large computational expense of the IQA-MPn approach is compensated by the advantages that IQA offers compared to older non-topological energy decomposition schemes. This expense is problematic in the construction of a machine learning training set to create kriging models for topological atoms. However, the algorithm presented here markedly accelerates the calculation of atomically partitioned electron correlation energies. Then again, the algorithm cannot calculate pairwise interatomic energies because it applies analytical integrals over whole space (rather than over atomic volumes). However, these pairwise energies are not needed in the quantum topological force field FFLUX, which only uses the energy of an atom interacting with all remaining atoms of the system that it is part of. Thus it is now feasible to generate accurate and sizeable training sets at MPn level of theory.