First-principles thermodynamical calculations and experimental confirmation of the phase diagrams of ceramic systems

对氧化物二元系的相界、相变和化合物的形成进行了系统的第一性原理热力学计算。为了验证理论结果，还对包括过饱和固溶体在内的各种样品进行了实验表征。在实验数据的基础上，发展了适用于实际热力学模拟的计算方法，并结合除尘器展开技术、蒙特卡罗模拟和第一性原理晶格静力学和动力学方法进行了计算。由晶格动力学计算得到比热，然后由积分得到自由能函数。利用DUSTER展开和蒙特卡罗方法，对二元体系中可能的相平衡结构和生成能进行了预测。对陶瓷样品和脉冲激光沉积制备的过饱和固溶体薄膜进行了x射线衍射和x射线能谱实验，验证了理论结果。结果揭示了各种氧化物二元系的原子结构、热力学性质、相界、相变行为和化合物的形成。这些例子包括对SnO-O系中形成新系列同质相的理论预测，以及对ZnO-MgO、ZnO-Al_2O_3、Ga_2O_3-MNGA_2O_4伪二元系中局域原子结构的测定。

Systematic first-principles thermodynamical calculations were performed to predict the phase boundary, phase transition, and compound formation in oxide binary systems. To confirm the theoretical results, experimental characterization was also conducted for a variety of specimens including supersaturated solid solutions. Computational methods for realistic thermodynamical simulations were developed on the basis of the experimentally obtained information.A combination of duster expansion technique, Monte Carlo simulations, and first-principles lattice statics and dynamics methods was used for the calculations. Specific heat was obtained from the lattice dynamics calculations, and free energy function was then derived from the integration. Using the duster expansion and Monte Carlo techniques, equilibrium structures and formation energies were predicted for possible phases in binary systems. The theoretical results were confirmed by experiments, such as x-ray diffraction and x-ray spectroscopy for ceramic specimens and the thin films of supersaturated solid solutions made by the pulsed laser deposition. As a result, atomic structures, thermodynamical properties, phase boundaries, phase transition behavior and compound formation were revealed for a variety of oxide binary systems. The examples include the theoretical prediction of the formation of new series of homologous phases in the Sn-O system and the determination of the local atomic structures in the ZnO-MgO, ZnO-Al_2O_3, Ga_2O_3-MnGa_2O_4 pseudo-binary systems.