Modeling Molecular Crystals by QM/MM: Self-Consistent Electrostatic Embedding for Geometry Optimizations and...

Area of Science:

• Computational Chemistry
• Solid-State Chemistry
• Materials Science

Background:

• Accurate modeling of molecular crystals is essential for understanding solid-state properties.
• Traditional methods often struggle to capture the interplay between quantum mechanical and environmental effects in crystals.

Purpose of the Study:

• To develop and validate an adaptive quantum mechanics/molecular mechanics (QM/MM) protocol for modeling molecular crystals.
• To accurately predict solid-state geometries and molecular properties.

Main Methods:

• An adaptive QM/MM protocol embedding a QM-described molecule in a molecular mechanics (MM) environment.
• Self-consistent charge calculations and fitting of additional charges for electrostatic effects.
• Geometry optimization using QM/MM with subsequent property calculations.

Main Results:

• Successfully modeled gas-to-solid bond contraction in HCN-BF3.
• Reproduced periodic-DFT quality local geometries for solid VOCl3 and a ruthenium allyl complex.
• Demonstrated suitability for solid-state property calculations, including NMR and EFG parameters.

Conclusions:

• The developed QM/MM protocol accurately models molecular crystal geometries and properties.
• This method provides a robust approach for solid-state computational chemistry, enabling accurate prediction of molecular behavior in crystalline environments.