First-principles anisotropic constitutive relationships in β-cyclotetramethylene tetranitramine (β-HMX)

Abstract

First-principles density functional theory calculations have been performed to obtain constitutive relationships in the crystalline energetic material ␤-cyclotetramethylene tetranitramine ͑␤-HMX͒. In addition to hydrostatic loading, uniaxial compressions in the directions normal to the ͕100͖, ͕010͖, ͕001͖, ͕110͖, ͕101͖, ͕011͖, and ͕111͖ planes have been performed to investigate the anisotropic equation of state ͑EOS͒. The calculated lattice parameters and hydrostatic EOS are in reasonable agreement with the available experimental data. The uniaxial compression data show a significant anisotropy in the principal stresses, change in energy, band gap, and shear stresses, which might lead to the anisotropy of the elastic-plastic shock transition and shock sensitivity of ␤-HMX.

Density functional theory calculations of anisotropic constitutive relationships in alpha-cyclotrimethylenetrinitramine

“…In contrast to our previous results on PETN ͑Ref. 23͒ and HMX, 24 there is a substantial deviation of the theoretical EOS from experiment. A similar problem has been encountered in previous calculations of hydrostatic compression of RDX by Byrd and Rice, 22 and this disagreement is attributed to poor description of van der Waals interactions by DFT.…”

“…23͒ and HMX. 24 Further, the lattice parameters and unit-cell volume are overestimated, which is a typical result of the PBE generalized gradient approximation functional. It has been suggested that the poor description of van der Waals interactions in DFT functionals is responsible for the overestimation of the unit-cell size for molecular crystals.…”

Analysis of thermomechanical response of polycrystalline HMX under impact loading through mesoscale simulations

“…[1][2][3][4][5] Heating due to each of these mechanisms depends on the histories of the states of local stress and rate of deformation in the material. Existing literature examines the behavior of energetic crystals and polymer-bonded explosives (PBXs) in two general forms: as single crystals with anisotropic material properties, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] and as heterogeneous collections of energetic grains with isotropic material properties. [23][24][25][26][27] The single crystal simulations have been carried out using both discrete methods (e.g., molecular dynamics (MD) and density functional theory (DFT)) [6][7][8][9][10][11][12][13][14][15][16] and continuum scale methods.…”

“…Existing literature examines the behavior of energetic crystals and polymer-bonded explosives (PBXs) in two general forms: as single crystals with anisotropic material properties, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] and as heterogeneous collections of energetic grains with isotropic material properties. [23][24][25][26][27] The single crystal simulations have been carried out using both discrete methods (e.g., molecular dynamics (MD) and density functional theory (DFT)) [6][7][8][9][10][11][12][13][14][15][16] and continuum scale methods. [17][18][19][20][21] Analyses utilizing discrete methods have yielded understanding of many of the thermo-mechanical properties of the polymorphs of HMX including crystal structure and lattice parameters, 11 isotherms, 10 elastic constants, 7 viscosity, 6 thermal conductivity, and behavior in compression.…”

Searching for new energetic materials: Computational design of novel nitro-substituted heterocyclic explosives

“…a clear understanding of the relationships between thermal stability of materials, their molecular and crystalline structures, and chemical properties remain unachieved 8 . With tremendous progress in the development of computer hardware and computational algorithms, theoretical modeling has become a powerful tool for exploration of physicochemical properties of explosive materials including the geometry and electronic structure, 9,10 thermal stability, 11,12,13 and the materials' response to mechanical impact 14,15,16 . A close collaboration between synthetic chemists, researchers who perform advanced characterization tests of materials, and those who analyze materials with theoretical and computational quantum-chemical methods prove to be particularly effective1 ,17 .…”