A transferable quantum mechanical energy model for intermolecular interactions using a single empirical parameter

The calculation of intermolecular interactions in molecular crystals using model energies provides a unified route to understanding the complex interplay of driving forces in crystallization, elastic properties and more. Presented here is a new single-parameter interaction energy model (CE-1p), extending the previous CrystalExplorer energy model and calibrated using density functional theory (DFT) calculations at the !B97M- V/def2-QZVP level over 1157 intermolecular interactions from 147 crystal structures. The new model incorporates an improved treatment of dispersion interactions and polarizabilities using the exchange-hole dipole model (XDM), along with the use of effective core potentials (ECPs), facilitating application to molecules containing elements across the periodic table (from H to Rn). This new model is validated against high-level reference data with outstanding performance, comparable to state- ofthe-art DFT methods for molecular crystal lattice energies over the X23 set (mean absolute deviation 3.6 kJ mol(-1)) and for intermolecular interactions in the S66x8 benchmark set (root mean-square deviation 3.3 kJ mol(-1)). The performance of this model is further examined compared to the GFN2-xTB tight-binding model, providing recommendations for the evaluation of intermolecular interactions in molecular crystal systems.

Automated summary

A new single-parameter interaction energy model is presented in this article, which calculates intermolecular interactions in molecular crystals and provides a better understanding of the complex interplay of driving forces. The model is calibrated using density functional theory calculations and validated against high-level reference data, showing outstanding performance in evaluating molecular crystal lattice energies and intermolecular interactions. The model is also compared to other methods, providing recommendations for the evaluation of intermolecular interactions in molecular crystal systems.