Typical Thermodynamic And Kinetic Properties Of Solid-liquid Interface: A Molecular Dynamics Simulations

It is important to study properties of the solid-liquid interface for understanding the wetting ability of liquid or the nucleation and growth of crystal. With the develop-ment of the computer technology, A possible method is to research the properties of the solid-liquid interface by computer simulations. Up to date, the most understanding in atomic scale is obtained from computer simulations. In this thesis, we studied the ther-modynamic and kinetic properties of the solid-liquid interface by molecular dynamics simulations.Main results of the thesis are as following:(1) The wetting properties of nano droplets on a solid surface are studied system-atically and the liquid structure near the interface is analyzed. Our researches focus mainly on the problem that influence from the details of interaction to the solid-liquid structure and the wetting properties. The results show that adding of the many body parameters, increasing distance or intensity of interaction will lead to the decrease of the contact angle. With the increase of interaction strength, the mismatch between the liquid atom and the solid atom affects the contact angle more strongly. By analyzing the liquid near interface, we find that the second peak of the pair correlation function splited under the condition of strong interaction and slight mismatch between the solid and liquid atomic size.(2) The wetting properties of Fe liquid droplet filled in carbon nanotubes (CNTs) and on graphene sheet are researched. Our simulations show that the contact angle decreases with the increasing the droplet size for Fe liquid droplet on graphene sheet. The contact angle decreases with increasing the CNT diameter for droplet in the CNT. Furthermore, its value independent of the length of the filled liquid. In the simulation, we estimate the value of the three-phase line tension for the condition of liquid droplet on graphene sheet following the modified Young equation. According to the analysis, both the radial and the axial number density in the CNT fluctuates. Furthermore, the periodic length of density oscillation is the same as the periodic length of the CNT.(3) The solidified behavior of the metal nanodroplets filled in the CNTs during the cooling process. We find that the solidified structures are affected both by the diameter of the CNTs and by the interaction strength between metal and carbon atoms. When the interaction is strong, the solidified metal structure form a multishell structure because the influence of the CNT wall. When the interaction is week, the solidified metal has a crystal structure.(4) The interface temperature gradient is investigated during the process of so-lidification. It is found that the systematic length in the growth direction affects the temperature gradient near the interface strongly. Considering the temperature gradi-ent, we calculate the dynamic coefficients of the Mg and Fe using the real temperature, which are about twice as the values calculated by the thermostat one. The anisotropy properties are determinate as the same system is used no matter which temperature is used.