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Molecular dynamics studies of phase changes in condensed matter
Abstract
Molecular dynamics (MD) simulation is a widely used theoretical tool for exploring the properties of condensed matter systems. This dissertation, which describes our research work on various types of phase changes in solids and liquids by MD simulations, consists of two parts: part I (chapters 1 $\sim$ 3) covers MD simulations of finite systems; part II (chapters 4 $\sim$ 6) covers infinite lattices. Chapter 1 describes simulations of the interface between two mixing liquids. We show that the macroscopic fractal-like properties of the interface also exist at the atomic-level, and that a fractal dimension analysis, for which we have developed a definite method, can be performed at and above the scale of a few interatomic spacings. Chapter 2 describes simulations of shock-induced detonation processes in systems with a generalized reactive three-body potential. We demonstrated the sensitivity of detonation initiation to the existence of boundaries and surfaces. Chapter 3 describes simulations of laser ablation. Our results show that pure local ionization of atoms lead to a clean removal of materials from surfaces, while a pure local heating only damages the surfaces badly. In Chapter 4, we derived the effective masses of the three basis vectors which define the supercells in MD simulations, and showed that these masses are uniquely determined by the lattice size and shape, and the shape of the supercell. We also developed an improved cooling technique for finding the ground state of a lattice. Chapters 5 $\sim$ 6 are the major parts of this dissertation. Chapter 5 describes the realization of the Potential-Induced Breathing (PIB) model in MD. With the PIB potentials, we performed simulations of high-pressure processes, melting, and phase transitions in ionic crystals, and compared the results with those using the Gordon-Kim potentials. Then in chapter 6, we developed an improved version of PIB potentials. Simulations show that these potentials are better than the original PIB potentials in simulating structural phase transitions but not the high-pressure processes in some compounds.
Subject Area
Condensation
Recommended Citation
Cao, Huazhe, "Molecular dynamics studies of phase changes in condensed matter" (1993). ETD collection for University of Nebraska-Lincoln. AAI9415952.
https://digitalcommons.unl.edu/dissertations/AAI9415952