Fig. 4.

Atomistic simulations of the tribochemical mechanism leading to reduction in friction. a–d Atomic snapshots from RMD simulations at selected times during the sulfur-induced amorphization of diamond nanoparticle. e–h Atomic snapshots from RMD simulations at selected times during the formation of OLC structures from amorphous carbon matrix containing uniformly dispersed S atoms (15% S concentration). i pair distribution functions of C-C for each snapshot shown in a, b. j Volumetric strains in the diamond lattice (Top) induced by substituting a C atom with different impurity atoms, and the corresponding defect energies E_d (Bottom) obtained from DFT calculations. In panels a–d, and e–h, the temperatures corresponding to the atomic snapshots are provided. In panel j, ΔV refers to change in the volume of diamond lattice owing to introduction of a substitutional defect, and V₀ refers to the volume of diamond lattice at equilibrium