Molecular Dynamics Simulation And The Preliminary Application In Geophysics

Numerical simulation has played more and more important roles in Geophysics as the development of computer for the past few years. Usually, computational methods are used to calculate synthetic seismogram in seismology and convection model in Geodynamics, while they are less used in investigating mineral physics. In recent years, molecular dynamics (MD) simulation has been used in Geophysics step by step. MD is used in researching macro-materials from the perspective of the atomic and molecular scale, which helps us to investigate the materials in the interior of the Earth.This thesis, firstly, discusses principle and realization methods of classical molecular dynamics simulation. MD is rooted in ancient atomic theory and its theory foundation is Newton's law of motion. Its basic principle is through simulating the motion process of nucleus in many body system, then to statistic the structure and properties of the system. The first MD simulation is by Alder and Wainwriht in 1957. After the part, the thesis reviews recent research on the MD simulation of the Earth's core in progress and of metal materials research status of solid-liquid phase line. And the last section of the part shows our study on impact behavior, e.g. agglomeration, of nano single crystal Cu ball and amorphous SiO2 ball.The last part of the thesis introduces one of our research results, the release melting of shock-loaded single crystal Cu, from a new aspect to show the atomistic processes and physics during release. A system that contains atoms about 105 is chosen, and the method to generate shock waves is using a flyer plate-target configuration with impact direction <100> of single crystal Cu. After the impact of flyer and target plates, two shock waves propagate to interior of two plates and reflect after reach the free surfaces as rarefaction waves, which unloaded the shocked material to partially or fully released states. We investigate several different piston velocities in 2~3km/s, for u p≥2.5km/s(above 170 GPa), release melting occurs continuously, and a sustained fully released state (liquid) can be achieved. The shocked crystal may undergo noticeable superheating before release melting. The release path can be regarded as an isentrope regardless of release melting.