LUNAR: Automated Input Generation and Analysis for Reactive LAMMPS Simulations

Generating molecular models for the LAMMPS molecular dynamics (MD) simulation software package is a difficult task and is an impediment to more widespread and efficient use of MD in materials design and development. Fixed-bond force fields generally require manual assignment of atom types, bonded interactions, charges, and simulation domain sizes. A new LAMMPS pre- and post-processing toolkit (LUNAR) is presented that efficiently builds molecular systems for LAMMPS. LUNAR automatically assigns atom types, generates bonded interactions, assigns charges and provides initial configuration methods to generate large molecular systems. LUNAR can also incorporate chemical reactivity into simulations using fixed-bond force fields by facilitating the use of the REACTER protocol. Additionally, LUNAR provides post-processing for free volume calculations, cure characterization calculations, and property predictions from LAMMPS thermodynamic outputs. LUNAR has been validated via building and simulation of pure epoxy and cyanate ester polymer systems with comparison of the corresponding predicted structures and properties to benchmark values, including experimental results from the literature. LUNAR provides the tools for the computationally-driven development of next-generation composite materials in the Integrated Computational Materials Engineering (ICME) and Materials Genome Initiative (MGI) frameworks.