Molecular Dynamics Simulations In Two-Dimensional Quasicrystals

Molecular dynamics (MD) simulation is a computational tool used for researchingdifferent quasicrystalline structures and understanding the formation mechanism. In theresearch of quasicrystals, MD can be used to study quasicrystalline structure, stability andequilibrium properties. In this thesis, we use MD simulations to simulate quasicrystalformation in two dimensions to generate quasicrystals with12-fold and18-fold rotationalsymmetry.Firstly, MD method is introduced including the basic theory, main algorithms, ensemblesand calculation details. We summarize the results obtained in the previous study ofquasicrystals with MD.Secondly, we propose the potentials based on the standard Lennard-Jones potential withthe Gaussian terms added, which change the position and width of wells and even causedouble-well potential. We try to find new quasicrystalline structures in different potentialparameters and simulation conditions.Lastly, we carry out a series of MD simulations and find the parameters and conditions ofthe formation of quasicrystals. Using the same potential parameters, there are differentstructures formed in different temperature and density. For certain temperature and density,quasicrystals can be formed within parameter ranges of the center, width and depth of theGaussian potential. In order to understand the quasicrystal structures and formationmechanism, we study the radial distribution function, static structure factor and the systemtotal energy to analyze the process and results of simulations.The most important result of this thesis is the formation of quasicrystals with18-foldrotational symmetry. Although this kind of structure have been reported in the previoustheoretical and experimental studies, it is the first finding in molecular dynamics simulations.This work suggests that quasicrystals have very rich structures and a lot of new things need tobe investigated.