Assessment and Optimization of Force Fields for Glycine Polymorphism and Solution Properties

Area of Science:

• Computational chemistry
• Materials science
• Crystallography

Background:

• Accurate force fields are crucial for molecular dynamics (MD) simulations of glycine crystal growth.
• Existing force fields often fail to reproduce properties for all glycine polymorphs (α, β, γ).

Purpose of the Study:

• To evaluate and recalibrate force fields for accurate simulation of glycine crystal polymorphs.
• To develop an optimized force field for predicting crystal and solution properties of glycine.

Main Methods:

• Extensive evaluation of 18 force field variants (OPLS and GAFF).
• Recalibration using multiobjective Bayesian optimization.
• Calculation of crystal lattice energies, densities, mechanical stability, solution densities, diffusion coefficients, and enthalpies.

Main Results:

• Optimized nonbonded parameters in OPLS variants significantly improved prediction of crystal properties for all polymorphs.
• The developed force field accurately reproduces relative polymorph stability, mechanical stability at elevated temperatures, and experimental data.
• Excellent agreement was achieved for lattice energies, crystal densities, and solution enthalpies.

Conclusions:

• The optimized force field provides accurate insights into glycine polymorphism in various environments.
• The developed optimization framework offers a generalizable approach for improving force fields for other molecular crystals.