Influence of interatomic bonding potentials on detonation properties

Abstract

The dependences of the macroscopic detonation properties of a two-dimensional (2D) diatomic (AB) molecular system on the fundamental molecular properties were investigated. This includes examining the detonation velocity, reaction zone thickness, and critical width as functions of the exothermicity (Q) of the gas-phase reaction [AB --> (1/2)(A(2) + B(2))] and the gas-phase dissociation energy (D(e)(AB)) for AB --> A + B . Following previous work, molecular dynamics (MD) simulations with a reactive empirical bond-order potential were used to characterize the shock-induced response of a diatomic AB molecular solid, which exothermically reacts to produce A2 and B2 gaseous products. Nonequilibrium MD simulations reveal that there is a linear dependence between the square of the detonation velocity and both of these molecular parameters. The detonation velocities were shown to be consistent with the Chapman-Jouguet (CJ) model, demonstrating that these dependences arise from how the equation of state of the products and reactants are affected. Equilibrium MD simulations of microcanonical ensembles were used to determine the CJ states for varying Q 's, and radial distribution functions characterize the atomic structure. The character of this material near the CJ conditions was found to be somewhat unusual, consisting of polyatomic clusters rather than discrete molecular species. It was also found that there was a minimum value of Q and a maximum value of (D(e)(AB)) for which a pseudo-one-dimensional detonation could not be sustained. The reaction zone of this material was characterized under both equilibrium (CJ) and transient (underdriven) conditions. The basic structure is consistent with the Zeldovich-von Neumann-Döring model, with a sharp shock rise and a reaction zone that extends to 200-300 Angstrom. The underdriven systems show a buildup process which requires an extensive time to approach equilibrium conditions. The rate stick failure diameter (critical width in 2D) was also found to depend on Q and (D(e)(AB)). The dependence on Q could be explained in terms of the reaction zone properties.

Molecular dynamics simulations of weak detonations

“…This √ E dependence was obtained in Ref. [35] in MD simulations of detonations in the REBO model and in Ref. [36] in another crystal model.…”

Simulations of Deformation Processes in Energetic Materials

“…They considered a number of geometric arrangements of circular voids including single voids, voids on square and triangular lattices, and randomly arranged voids. Although the AB system is a highly idealized model, it captures many features of reactive waves in real materials (Heim, 2007(Heim, , 2008a(Heim, , 2008b. Fig.…”

Molecular dynamics simulations of detonation on the roadrunner supercomputer

“…The computation of forces scales linearly with the number of atoms, N, since there are no long-range interactions. Recently, only twodimensional (2D) simulations have been available for studies such as detonation instability [3][4][5][6][7][8] and hot-spot mediated detonation [9]. Threedimensional (3D) simulations are more desirable since the heat capacity is larger and richer physics can be expected, but these require vastly more computing power.…”