Using the example of cyclic twins of CVD diamond, their pseudo-pentagonal and icosahedral forms have been described. It is shown that their general appearance is determined by simple habit forms of crystals (octahedron and cube) in the case of cyclic twinning in accordance with the spinel law on (111) plane. The varieties of cyclic twins are identified. A topographic characteristic of cube and octahedron faces of these complex twins is provided. Models for the formation of pseudo-pentagonal and icosahedral forms of diamond crystals are proposed.

中文翻译：

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CVD钻石晶体的循环孪晶

以CVD金刚石的环状孪晶为例，已经描述了它们的伪五边形和二十面体形式。结果表明，根据（111）平面上的尖晶石定律，在循环孪晶的情况下，它们的一般外观由晶体（八面体和立方）的简单习性形式决定。确定了环状双胞胎的种类。提供了这些复杂孪晶的立方和八面体面的形貌特征。提出了形成假五角形和二十面体形式的金刚石晶体的模型。