The propagation of shock-induced detonations in an inhomogeneous sample is studied at the microscopic level by molecular dynamics. The model consists of a two-dimensional lattice of diatomic molecules connected by Morse potentials. A predissociative intramolecular potential is used. Simulations in a perfect crystal exhibit two detonation regimes: a fast regime, in which the atomic motions are very coherent, and a slow regime, which is the regime observed experimentally. The propagation of the detonation wave across grain boundaries, domains with a different orientation, vacancies, and a region where the chemical reaction started earlier due to a hot spot, is investigated. The slow-detonation regime is found to be very robust, showing that the structure observed at the microscopic level could persist in a real polycrystalline sample. The fast-denonation regime is highly sensitive to perturbations and tends to evolve into fingerlike structures. Its possible relevance in some systems is discussed.

• Received 24 July 1991

DOI:https://doi.org/10.1103/PhysRevB.45.9551