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Vibrational and thermodynamic properties of β-HMX: A first-principles investigation

Authors :
Rajiv K. Kalia
Aiichiro Nakano
Zhongqing Wu
Priya Vashishta
Source :
The Journal of Chemical Physics. 134:204509
Publication Year :
2011
Publisher :
AIP Publishing, 2011.

Abstract

Thermodynamic properties of β-HMX crystal are investigated using the quasi-harmonic approximation and density functional theory within the local density approximation (LDA), generalized gradient approximation (GGA), and GGA + empirical van der Waals (vdW) correction. It is found that GGA well describes the thermal expansion coefficient and heat capacity but fails to produce correct bulk modulus and equilibrium volume. The vdW correction improves the bulk modulus and volume, but worsens the thermal expansion coefficient and heat capacity. In contrast, LDA describes all thermodynamic properties with reasonable accuracy, and overall is a good exchange-correlation functional for β-HMX molecular crystal. The results also demonstrate significant contributions of phonons to the equation of state. The static calculation of equilibrium volume for β-HMX differs from the room-temperature value incorporating lattice vibrations by over 5%. Therefore, for molecular crystals, it is essential to include phonon contributions when calculated equation of state is compared with experimental data at ambient condition.

Details

ISSN :
10897690 and 00219606
Volume :
134
Database :
OpenAIRE
Journal :
The Journal of Chemical Physics
Accession number :
edsair.doi.dedup.....3d83833d925e714e22adec6799004a86
Full Text :
https://doi.org/10.1063/1.3587135