Impact of surface energy on the shock properties of granular explosives

X Bidault and N Pineau, JOURNAL OF CHEMICAL PHYSICS, 148, 034704 (2018).

DOI: 10.1063/1.5009072

This paper presents the first part of a two-fold molecular dynamics study of the impact of the granularity on the shock properties of high explosives. Recent experimental studies show that the granularity can have a substantial impact on the properties of detonation products i.e., variations in the size distributions of detonation nanodiamonds V. Pichot et al., Sci. Rep. 3, 2159 (2013) g. These variations can have two origins: the surface energy, which is a priori enhanced from micro-to nano-scale, and the porosity induced by the granular structure. In this first report, we study the impact of the surface-energy contribution on the inert shock compression of TATB, TNT, alpha-RDX, and beta-HMX nano-grains (triaminotrinitrobenzene, trinitrotoluene, hexogen and octogen, respectively). We compute the radius-dependent surface energy and combine it with an ab initio-based equation of state in order to obtain the resulting shock properties through the Rankine-Hugoniot relations. We find that the enhancement of the surface energy results in a moderate overheating under shock compression. This contribution is minor with respect to porosity, when compared to a simple macroscopic model. This result motivates further atomistic studies on the impact of nanoporosity networks on the shock properties. Published by AIP Publishing.