Ab initio calculation of the interaction between neutral and charged silicon nanoclusters

In dusty plasmas, the formation of nanoclusters marks the beginning of the coagulation stage, leading to the rapid generation of larger particles. In this work, we present an overview of the interaction between silicon nanoclusters (SNCs) of about 1 nm diameter within the framework of density functional theory (DFT), taking into account chemical, van der Waals, and multipolar electrostatic interactions. Two types of SNCs are considered: particles composed entirely of silicon (Si-30, Si-40, Si-50, Si-60) and a particle whose dangling bonds are occupied by hydrogen atoms (Si29H24). The interaction energies obtained between two neutral or weakly charged SNCs all have a repulsive part at a short separation distance, followed by a minimum corresponding to a stable state of coagulation due to chemical bonds between the particles. In particular, our calculations show that: (1) the Hamaker constant (which characterizes the London-type van der Waals interaction) depends on the pair of identical SNCs, (2) the multipolar electrostatic contribution at large separation distances allows the extraction of the charged SNC polarization coefficient, and (3) the coagulation rates between SNCs are significantly higher than previously estimated.