Theoretical study of phonon density of states, thermodynamic properties and phase transitions for HMX

Abstract

We develop a physical model to describe the phonon density of states for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and use it to calculate a set of thermodynamic properties, such as the thermal expansion coefficient, bulk modulus, specific heat and Hugoniot curve. The results are in good agreement with available experiments at low pressure and provide reasonable prediction at high pressure for the lack of experiments. Two types of phase transitions are compared: static phase transition and shock-induced phase transition. We determine that the phase transition curves of the two mechanisms are quite different. The pressure to induce an phase transition for HMX by shock loading is larger than that under a static condition.

Keywords:

• GGA + vdW
• phonon density of states
• thermodynamic property
• Hugoniot curve
• phase transition

Acknowledgements

The authors gratefully acknowledge Professor D.Q. Wei and Dr S. Liu for supporting HMX models.

Notes

1 This work is supported by the National Natural Science Foundation of China [grant number 11004011], [grant number 11172048], the Development Foundation of China Academy of Engineering Physics [grant number 2011A0101001], and the Defence Industrial Technology Development Program [grant number B1520132013].