干旱区生态环境知识资源中心

We present thermodynamic models for the five most commonly studied phases of the energetic material octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine.(HMX): liquid HMX and four solid polymorphs (alpha-, beta-, gamma-, and delta-HMX). We show results for the density, heat capacity, bulk modulus, and sound speed, as well as a phase diagram that illustrates the temperature and pressure, regions over which the various HMX phases are most thermodynamically stable. The models are based on the same equation of state presented in our recently published paper [Myint et al., Ind. Eng. Chem. Res., 2016, 55, 2252] on another energetic material, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). We combine our HMX arid RDX models together so that the equation of state can also be applied to liquid and solid mixtures of HMX/RDX. This allows us to generate an HMX/RDX phase diagram and calculate the enthalpy change associated with.a few different kinds of phase transitions that these mixtures may undergo. Our.paper is the first to present a single equation of state that is capable of modeling both pure HMX and HMX/RDX mixtures. A distinct feature of HMX is the strongly metastable nature of its polymorphs. This has caused some ambiguity in the literature regarding the thermodynamic stability of, alpha-HMX. By examining possible arrangements for the relative order of the six different solid solid transition (alpha-beta, alpha-gamma, alpha-delta, beta-gamma, beta-delta, and gamma-delta) temperatures, we conclude that alpha-HMX must be thermodynamically stable so that the HMX phase diagram must have an alpha phase region.