Molecular dynamics modelling of nanocarbon cluster properties under conditions close to HE detonation

Russian Federal Nuclear Centre – Zababakhin Institute of Applied Physics (RFNC-VNIITF), 456770 Snezhinsk, Russia

^a e-mail: i.v.derbenev@vniitf.ru

Abstract

We use molecular dynamics for modelling properties of carbon nanoclusters. The size of modelled carbon nanoclusters is below 5 nm, which is typical of detonation diamond nanoclusters. We have found their structural changes at P = 0 to be as follows: Diamond → Diamond core + GL-surface → sandwich-type graphite → Graphite-like liquid. In smaller clusters the transformations start at a lower temperature. Adaptive Template Analysis (ATA) was used to determine the structures. We studied evaporation properties at temperatures above 5000 K. For clusters of several thousands of atoms, the simple dependence k_vap ∼ e^−T₀/T/N^1/3 (T₀ is constant) is quite good. It has been found out that densities of saturated vapour for clusters containing from 4000 to 8000 atoms are very close at T = 5000 K. The structure of nanoclusters was studied at nonzero pressures set by an argon environment. Calculated results suggest that the patterns for different temperatures are qualitatively similar for three pressures under study (20, 25 and 30 GPa). At T = 1000–1500 K, the initial diamond core is preserved and a thin disordered GL layer is present on the surface. At T = 2000–5000 K, graphite grains form in the sample and a thin layer of liquid is present on its surface. The sample is amorphous at 5500 K and 6000 K. The prevalence of the graphite phase at these pressures seems to come from the absence of long-range interaction in REBO-2002.