Atomistic modeling of materials under extreme pressure

Abstract: This thesis is dealing with simulation of polycrystalline materials underthe conditions of anisotropic pressure and temperature. Work has been carriedout in three steps:ˆ Research of the inuence of point defects and grain boundaries on theprocess of melting. The inuence of defects' concentration, grain sizeand lattice direction mismatch on the superheating temperature wasstudied.ˆ Investigation of the boundaries of application of the metadynamics methodto the simple atomic model with Buckingham interaction. The solidsolidphase transition, where one of the phases has temperature inducedstability was conrmed. We found the optimal size of simulation boxto study the solid-solid phase transitions using the metadynamics technique.ˆ A model of polycrystalline materials based on macroscopic approximationwas formulated. This model was applied to the model of the polycrystallinematerial using cellular automata. Using this approximationthe eect of anisotropic stress caused by anisotropic heating was studied.