Particle-based multiscale coarse graining with density-dependent potentials: application to molecular crystals...

Area of Science:

• Computational Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Developing accurate coarse-grain models is crucial for simulating complex materials like hexahydro-1,3,5-trinitro-s-triazine (RDX).
• Existing methods often struggle to capture the behavior of crystalline phases under varying pressures.

Purpose of the Study:

• To develop and validate isotropic particle-based coarse-grain models for crystalline RDX.
• To introduce a novel theory for local density-dependent multiscale coarse-graining (MS-CG) potentials.

Main Methods:

• Utilized the multiscale coarse-graining (MS-CG) method, a particle-based force-matching approach.
• Parameterized one-site and four-site coarse-grain (CG) models from atomistic simulations.
• Implemented density-dependency through interpolation of MS-CG force fields derived at reference densities.

Main Results:

• The one-site MS-CG model accurately describes the atomistic lattice structure of α-RDX at ambient and high pressures.
• The model reproduces elastic and vibrational properties, pressure-volume curves up to 10 GPa, and melting temperature.
• The model also captures correct pair and higher-order correlations in the molten state and shows potential in simulations of shocked crystalline RDX.

Conclusions:

• The developed density-dependent MS-CG model provides an accurate and computationally efficient representation of RDX across different phases and pressures.
• This approach enhances the applicability of coarse-grained simulations for energetic materials like RDX.