The Genesis of Twin Crystals
The Genesis of Twin Crystals
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DOI：
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发表时间：
1945-08
影响因子：
3.1
通讯作者：
M. Buerger
中科院分区：
文献类型：
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作者：
M. Buerger
最近人们对双胞胎发生的一个可能原因很感兴趣。显然，唯一流行的孪生方法是通过法国学派阐述的孪生经验规则。作者的观点，现在大约二十岁，在此提出作为一个理性的，结构性的方法对孪生的原因。由于稳定的晶体代表原子集合的最低能态，很明显孪晶界必须对应于更高的能态。结果表明，这种较高的能量在很大程度上与较高的配位原子的领域。孪晶的形成需要满足边界原子的第一配位条件。这种观点纯粹是结构性的，并且已经在双胞胎中得到了证实，双胞胎已经被认为是结构性的。根据发生的不同，双胞胎可分为生长双胞胎、转化双胞胎和滑行双胞胎。生长孪晶是由生长过程中偶然偏离平衡而引起的，并且在核阶段，特别是在过饱和条件下是有利的。相变孪晶是高低反转的结果。滑移孪晶是由塑性变形中的一种特殊类型的结构剪切引起的。分离的部分原因是孪晶界的高能量。孪晶的行为与从一种多晶型转变为另一种多晶型的行为类似：生长孪晶对应于重构转变;滑移孪晶对应于位移转变。变换孪生是非混合的一种特殊情况。人们常说，孪生是晶体努力使晶体具有更大对称性的结果，这与实际情况完全相反。
Interest has recently been indicated in a possible cause for the occurrence of twins. Apparently the only popular approach to twinning has been through the empirical rules of twinning enunciated by the French School. The writer's views, now some twenty years old, are herewith presented as a rational, structural approach to the cause of twinning. Since a stable crystal represents the least energy state of a collection of atoms, it is evident that the twin boundary must correspond with a higher energy state. It is shown that this higher energy is largely associated with the higher coordination spheres of the atoms. That a twin can form at all requires that the first coordination conditions of the atoms at the boundary are satisfied. This view is purely structural and has been substantiated in twins which have been considered with regard to structure. On the basis of genesis, twins may be divided into the categories of growth twins, transformation twins, and gliding twins. Growth twinning is caused by an accidental departure from equilibrium during growth, and is favored in the nuclear stage, especially under conditions of supersaturation. Transformation twinning is a consequence of high-low inversion. Glide twinning is caused by a specific type of structural shear in plastic deformation. Parting is, in part, a consequence of the high energy in the twin boundary. The act of twinning has analogies with the act of transforming from one polymorph to another: growth twinning corresponds with reconstructive transformation; glide twinning corresponds with displacive transformation. Transformation twinning is a special case of unmixing. The oft-repeated saying that twinning represents the result of an effort on the part of the crystal to assume a greater symmetry is the exact opposite of the true state of affairs.