【摘要】 采用第一性原理方法计算了BeO在零温时的高压相变和三种结构在零温零压时的声子谱.相变的计算表明,在122GPa左右的压力下BeO会发生从纤锌矿(B4)结构到氯化钠(B1)结构的相变,而闪锌矿(B3)结构在零温零压下是一种可能的亚稳态结构.采用冷声子方法计算了这三种结构的BeO在零温零压下的声子谱.计算结果表明:B1结构在零温零压下是一种不稳定的结构;尽管B4结构和B3结构具有明显的相似性,仍然可以通过声子谱来很好的区分.最后根据准简谐近似理论计算得到了BeO的高温高压相图.更多还原

【Abstract】 The high pressure phase transition at zero temperature and the phonon-dispersion relations at zero temperatue and zero pressue of BeO have been studied by a first-principles method.The results show that a phase transition from wurtzite structure(B4) to cubic sodium chloride structure(B1) happens at about 122 GPa and the zinc blende phase(B3) is of a meta-stable structure at zero temperature and zero pressure.The phonon-dispersion relations of B1,B3 and B4 phase BeO at zero temperature and zero pressure are investigated by the frozen phonon method.The calculations show that at zero temperature and zero pressure B1 phase is an unstable phase and B4 and B3 phases are of two very simliar structure,but they are still distinguishable from each other by their phonon-dispersion relations.Finally,the phase diagrams of BeO at high temperature and high pressure are studied.更多还原