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)]}. 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, α-
RDX, and β-
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.