Shock Wave Initiation of Pentaerythritol Tetranitrate Single Crystals:  Mechanism of Anisotropic Sensitivity

Abstract

A chemical mechanism to explain the observed anisotropy in the shock wave initiation of pentaerythritol tetranitrate (PETN) single crystals is proposed on the basis of semiempirical quantum chemical calculations. Building on the previously proposed model of steric hindrance to shear, the molecular mechanics of shear deformation at the lattice level is correlated with rotational conformations of PETN. The numerous stable conformations of PETN differ in symmetry and dipole moment values. The initial conformation belongs to the S 4 molecular point group and possesses no dipole moment. Because of shear deformations, the molecules change conformations. The [110] shocks result in sterically hindered shear and generate polar conformations. In contrast, the [100] shocks result in little or no polarization. Because the decomposition chemistry of PETN at 5−10 GPa is likely dominated by ionic reactions, local polarity of the lattice plays a crucial role in reactivity. The polar lattice stabilizes the transition state due to dipole−dipole interactions and, thus, facilitates the ionic dissociation. In contrast, the nonpolar lattice results in no stabilization and low reaction rates. Plausible ionic reactions are briefly discussed and experiments are suggested to verify the mechanism proposed.

Reaction mechanisms and sensitivity of silicon nitrocarbamate and related systems from quantum mechanics reaction dynamics

“…Experiments exposing the crystal to a high-energy laser, high-energy fracture, or high pressure found that Si-C/C-C and C-O bonds the first to break, which was interpreted to suggest that O-NO2 bond is relatively strong than these other bonds. [54][55][56] In contrast, we find that slower thermal decomposition leads to O-NO2 bond rupture as the initial step, which was also observed for low-energy fracture or low energy laser at ambient pressures. 55,57 As temperature increases above 1850 K, we observe the formation of NO, H, and HONO.…”

Theoretical Predictions of Lattice Parameters and Mechanical Properties of Pentaerythritol Tetranitrate under the Temperature and Pressure by Molecular Dynamics Simulations

“…In the past decades, many researches on the equation of state (EOS) and mechanical properties have been done for PETN by theory and experiments [1][2][3][4][5][6][7][8][9][10]. Accurate EOS and elastic constants are of particular importance because they provide an excellent opportunity to link the microscopic and macroscopic properties of PETN on atomic and molecular scale [1].…”

“…The chemical decomposition and mechanical deformation are dependent on the intermolecular interactions, molecular arrangements, and molecular composition [7,8]. The elastic constant is a key parameter to investigate the mechanism of a detonation initiation and mechanical deformation.…”

The Low-Temperature Vibrational Behavior of Pentaerythritol Tetranitrate

“…At atmospheric pressure, below the melting temperature of 141.3 °C (1), PETN appears as white crystals assembled into a tetragonal structure (P-42 1 c) with four molecules per unit cell arranged in an S 4 molecular symmetry. Both infrared (6,8,9) and Raman (9-10) characterizations of this phase exist, and several theoretical calculations of the vibrational frequencies of the crystal have been reported (8)(9)(10)(11)(12)(13). The mechanical properties of PETN at ambient conditions are quite interesting, as PETN exhibits a strong directional dependence to shock-initiated detonation (5,(14)(15)(16)(17)(18)(19)(20)(21)(22).…”