散射
结晶学
蒙特卡罗方法
衍射
化学
分子物理学
平面(几何)
k-最近邻算法
凝聚态物理
航程(航空)
对角线的
物理
材料科学
光学
几何学
数学
计算机科学
统计
人工智能
复合材料
作者
Andrew G. Christy,Ann‐Kristin Larsson
标识
DOI:10.1006/jssc.1997.7640
摘要
The compounds (Co, Ni)(Ge, Sn) and Cu1+xhave hexagonal average structures intermediate between those of NiAs and Ni2In. Ordering of atoms and vacancies in the partially occupiedA′ sites produces a variety of superstructures of lower symmetry. In the structures of this study, the modulation vector is always in the (hhl) plane. Diffuse scattering observed in some cases implies the occurrence of short-range order only. The effect of two-site interactions on determining the preferred long-range and short-range ordering patterns was investigated by using a Monte Carlo simulation technique to generate two-dimensional arrays of “atoms” and “vacancies” and calculating the corresponding scattering patterns. It is shown that many of the 18 symmetrically distinct first- and second-nearest-neighbor interaction energies are nonzero in these systems but that the preferred ordering pattern is in most cases determined by variation in only three second-nearest-neighbor terms. These three parameters vary with both composition and temperature. The undulating diffuse streaks observed in electron diffraction in the Sn-bearing and Co–Ge systems are shown to arise from a combination of negligible interactions along z, strong interactions in the xy plane, and weak diagonal interactions.
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