Elastic Properties of HMX

Abstract

Atomistic molecular dynamics simulations have been used to calculate isothermal elastic properties for β‐, α‐, and δ‐HMX. The complete elastic tensor for each polymorph was determined at room temperature and pressure via analysis of microscopic strain fluctuations using formalism due to Rahman and Parrinello [J. Chem. Phys. 76, 2662 (1982)]. Additionally, the isothermal compression curve was computed for β‐HMX for 0 ⩽ p ⩽ 10.6 GPa; the bulk modulus K and its pressure derivative K′were obtained from two fitting forms employed previously in experimental studies of the β‐HMX equation of state. Overall, the results indicate good agreement between the bulk modulus predicted from the measured and calculated compression curves. The bulk modulus determined directly from the elastic tensor of β‐HMX is in significant disagreement with the compression curve‐based results. The explanation for this discrepancy is an area of current research.