Crystal structure prediction of rigid molecules.

Area of Science:

• Computational chemistry
• Materials science
• Crystallography

Background:

• Accurate prediction of crystal structures is crucial for understanding material properties.
• Existing force fields often struggle to balance accuracy and computational efficiency for crystal structure prediction.
• Developing robust methods for unit-cell optimization and crystal structure searching is an ongoing challenge.

Purpose of the Study:

• To introduce a novel non-polarizable force field based on atomic multipoles for crystal structure prediction.
• To develop and validate methods for unit-cell optimization and crystal structure generation.
• To assess the efficiency and accuracy of the developed force field and algorithms in predicting experimental crystal structures.

Main Methods:

• A non-polarizable force field was developed using atomic multipoles, fitted to experimental crystal properties and ab initio gas-phase dimer data.
• The Ewald summation method was employed for calculating long-range electrostatic and dispersion energies in crystals.
• A space-group symmetry constraint was implemented for unit-cell optimization, alongside an algorithm for random crystal generation.

Main Results:

• The force field successfully reproduced experimental crystal properties and accurately calculated dispersion energies.
• Unit-cell optimization was performed on 4427 unit cells, with detailed results for flexible and rigid molecule optimizations.
• An average of X random crystals were needed to find the correct experimental structure for 2440 rigid single-component crystals, with the correct structure consistently ranked highly by the force field energy.

Conclusions:

• The developed force field and associated algorithms provide a powerful tool for accurate and efficient crystal structure prediction.
• The study demonstrates the feasibility of predicting crystal structures by searching over probable space groups.
• This work advances the field of computational crystallography and aids in the discovery of new materials.