Electrostatic interactions versus van der Waals interactions in the self-assembly of dispersed nanodiamonds

4-5 nm nanodiamonds tend to self-assemble into 100-200 nm nanodiamond aggregations and furthermore nanodiamonds in the early stages of the detonation process present fantastic twinned morphologies, indicating that there are strong interactions among these nanodiamonds. Herein, electrostatic interactions and van der Waals interactions between two nanodiamonds are explored using DFT computations in conjunction with Monte Carlo molecular simulations. It is indicated that the van der Waals forces are much stronger than the electrostatic forces for the unsaturated nanodiamonds. More importantly, two assembly features are exposed as follows: assembly has a preferential face-to-face orientation; assembly has a strong binding energy comparable to the dissociation energy of C-C bonding, which is 116.1 kcal mol(-1) for a 2.48 nm truncated octahedral nanodiamond. The results suggest that the strong forces holding the nanodiamond aggregation almost certainly attribute to the proposed strong van der Waals forces, which is of great importance in understanding the aggregative properties of nanodiamond.