Ab initio calculations on point defects in forsterite (Mg2SiO4) and implications for diffusion and creep
Ab initio calculations on point defects in forsterite (Mg2SiO4) and implications for diffusion and creep
复制标题
DOI：
10.2138/am-1997-11-1201
复制
发表时间：
1997-12
影响因子：
3.1
通讯作者：
J. Brodholt
中科院分区：
文献类型：
--
作者：
J. Brodholt
对镁橄榄石中简单离子空位的从头计算表明，不同位置上的空位之间存在着很大的能量差。在O3位置上的氧缺陷在能量上分别比在O2和O1位置上低1和3eV之间。镁缺陷的M1网站是0.8 eV的能量低于M2网站。这些巨大的能量差异意味着在不太有利的位置上有许多数量级的空位。在镁的情况下，扩散被认为是通过空位跳跃机制发生的，观察到的关于晶体学取向的各向异性可以通过跳跃必须仅从M1到M1位点的事实来合理化
Abstract Ab initio calculations on simple ionic vacancies in forsterite show that there are large energetic differences between vacancies on nonequivalent sites. Oxygen defects on the O3 site are between 1 and 3 eV lower in energy than on the O2 and O1 site, respectively. Magnesium defects on M1 sites are 0.8 eV lower in energy than on the M2 sites. These large energy differences mean that there are many orders of magnitude fewer vacancies on the less-favored sites. In the case of magnesium, where diffusion is thought to occur by means of a vacancy-hopping mechanism, the observed anisotropy with respect to crystallographic orientation can be rationalized by the fact that jumps must only be from M1 to M1 sites