Estimated probability of copper long-lived dimer formation in two particle collisions based on the molecular dynamics simulation

Knowing the mechanisms of birth, growth and development of nanoparticles is important for optimization of their production techniques. The majority of nanoparcticles production methods implies self-assembly from the liquid or gas phase. The initial stage of homogeneous nucleation from atomic vapor to a considerable degree specifies the ultimate size distribution of particles, which determines the topicality of its study. The paper presents a statistical analysis of the results of molecular dynamics simulation of metal (Cu) vapor nucleation in the inert gas atmosphere (Ar). The peculiar features of the initial stage of nucleation to estimate probability of diatomic molecule growth (Cu$_2$) in the supersaturated nonequilibrium medium are considered. It's shown that as a result of collision of two metal atoms an unstable dimer can be formed, which lifetime is comparable to time between metal atom collisions. Based on the results of the statistical analysis we assess the differential probability of forming the long-lived unstable dimer in two-particle interactions depending on the energy value of colliding particles in the system of their mass center. The integration of differential probability in terms of all energies with regard to theoretical energy distribution of copper atoms at the given temperature has allowed us to arrive at an integral estimate of the probability of forming the long-lived dimer in the Cu-Cu collision. It's been discovered that when increasing the temperature in the range of 300–1500 K the probability of formation is decreased from 0,86 % to 0,16 %.