The Kernel Energy Method Applied to Quantum Theory of Atoms in Molecules – Interacting Quantum Atoms (QTAIM-IQA) Energies

Abstract The kernel energy method (KEM) has been widely applied to predict the properties of large molecules from kernels fragments in a fast and reliable manner. Kernels are typically made of many atoms raising the question of whether the accuracy of KEM is traceable to the atomic level? An exact atomic decomposition of the molecular energy within the Quantum Theory of Atoms in Molecules (QTAIM), termed “Interacting Quantum Atoms (IQA)”, performed on a triglycyl model demonstrates that this is not the case. The Kernel energies are found to be up to an order of magnitude more accurate than the underlying IQA atomic energies. The accuracy of KEM energies is, thus, the result of a subtle cancellation of errors among the different atoms composing the kernels.