Anisotropic Thermal Expansion of CL-20 Polymorphs from <i>Ab initio </i>Molecular Dynamics Simulations

Hexanitrohexaazaisowurtizane (CL-20) is a high-density nitramine compound with several known polymorphs. Anisotropic thermal expansion coefficients for different polymorphs are needed to model effects of polymorphic impurities during thermal cycling. In this presentation, I will describe density functional theory (DFT) based molecular dynamics simulations of temperature-dependent lattice constants of the epsilon and gamma polymorphs and compare the results to available experimental data as well as predictions from density functional tight binding and ReaxFF-based molecular dynamics simulations.