Solid-state wetting at the nanoscale: molecular dynamics and surface diffusion approach

摘要

The authors simulated spreading of solid copper (Cu) and gold (Au) nanoparticles (5–7 nm size) on the (100) face of thernsame metal by using molecular dynamics. Then, the results obtained for the copper (nanoparticle)/copper (substrate)rnsystem were qualitatively compared to some available experimental data on the spreading of copper microparticlesrn(5–20 mm) on the surface of polycrystalline copper. Before simulating the nanoparticle spreading, the size dependence ofrnthe melting temperature was investigated for copper and gold nanoparticles. When temperatures were by 25–35 K lowerrnthan the copper particle melting temperature, the observed value 40° of the equilibrium contact angle qualitativelyrnagreed with the range 20–25° that the authors evaluated using an experimental snapshot of a copper microparticle onrnthe copper polycrystalline substrate at temperature by 33 K lower than the bulk copper melting point. However, therncharacteristic spreading times 0·5–10 ns found for nanoparticles in computer experiments differ from that for copperrnmicroparticles (3 h ≈ 10~5 s) by many orders of magnitude. The characteristic times of spreading for copper and goldrnnanoparticles were also estimated by using the capillary-induced surface diffusion concept, the similarity theory and anrnavailable experimental value of the spreading duration for solid copper microparticles. The theoretical estimations inrnquestion satisfactorily agree with the authors’ molecular dynamics results.