Complete Equations of State for Cyclotetramethylene Tetranitramine

Abstract

Complete equations of state for the volumetric deformation of the β-polymorph of cyclotetramethylene tetranitramine (β-HMX) have been derived from its Helmholtz free energy. Dispersion-corrected density functional theory calculations were used to compute the dependence of the frequencies of the vibrational normal modes on specific volume. The normal mode frequencies were used directly to generate both a tabular equation of state and an approximate model where the sum over normal mode fre-quencies is replaced by a set of five Debye models. Both the tabular and Debye model-based equations of state use the same cold curve, which is parameterized to the isothermal compression data of Yoo and Cynn [C. S. Yoo and H. Cynn, J. Chem. Phys., 1999, 111, 10229]. The two equations of state are applied to the calculation of the thermophysical properties of β-HMX required for continuum-level hydrodynamic simulations and are compared in detail.

Determining the mechanical and decomposition properties of high energetic materials (α-RDX, β-HMX, and ε-CL-20) using a neural network potential

“…For example, the primary deviation was observed in the C12 direction of RDX (7.30 GPa), 9 the C12 direction of b-HMX (12.07 GPa), 10 and the C11 dimension of e-CL-20 (12.61 GPa). 8 Furthermore, the elastic constants of a-RDX, b-HMX, and e-CL-20 crystals predicted by the NNP model exhibit reasonable consistency with the results obtained by Cawkwell et al 88 b-HMX, and e-CL-20 crystals are calculated using the above computed elastic constants in various dimensions (Table 3). The calculated values of the elastic constant, as well as B 0 , G, E, and m, indicate an excellent agreement between the predictions of the NNP model and previously theoretical values.…”

“…The calculated values of the elastic constant, as well as B 0 , G, E, and m, indicate an excellent agreement between the predictions of the NNP model and previously theoretical values. [88][89][90][91][92] Although the model shows a reasonable level of correspondence with experimental measurements, there still exists some level of discrepancy. 8,9,[85][86][87] This can be attributed to the fact that experimental measurements typically involve polycrystalline samples, which may contain defects and voids, whereas our calculations are based on perfect single crystals.…”

“…88 showed predicted MAEs as 3.05 AE 2.76, 5.01 AE 2.78, and 4.18 AE 5.72 GPa for a-RDX, b-HMX, and e-CL-20 crystals, respectively. Our NNP predicted results align closely with these values.…”

Dependence of the Elastic Stiffness Tensors of PETN, α‐RDX, γ‐RDX, ϵ‐RDX, ϵ‐CL‐20, DAAF, FOX‐7, and β‐HMX on Hydrostatic Compression

“…All of the DFT calculations were performed using the opensource code CP2k with the DZVP basis set, zero smearing of the electronic occupancies in the vicinity of the Fermi energy, Goedecker-Teter-Hutter pseudopotentials [48], the generalized gradient approximation (GGA) exchange-correlation functional of Perdew, Burke, and Ernzerhof (PBE) [49], and the D3(BJ) dispersion-correction of Grimme, Ehrlich, and Goerigk [50]. The mixed basis Gaussian and Plane Waves method used by CP2k used 4 multi-grids, a plane wave cut-off of 1200 Ry and a relative cut-off of 60 Ry, which our previous studies found gives well converged to-tal energies and forces at reasonable computational expense [51][52][53].…”

Equation of State for Single Crystal 3,3′-Diamino-4,4′-azoxyfurazan

“…9 For instance, the α V computed from our recent EoS for β-HMX underestimated values derived from X-ray diffraction experiments by about 30%. 10 In the absence of X-ray data, we compare the computed α V for single crystal DAAF to values derived from thermal strain data taken from polycrystalline samples pressed to ρ = 1.69 g/cm 3 , or about 97% of the theoretical maximum density. 39 Figure 9 shows that the α V derived from the polycrystalline samples exceed those calculated from the EoS by 200−300%.…”