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本文用负离子配位多面体生长基元理论模型讨论了多型性晶体表面螺旋结构的形成 ,提出在多型性晶体中配位多面体呈层状分布 ,配位多面体的面为层的边界 ,上、下层负离子配位多面体不是呈镜象对称的 ,在三方晶系和六方晶系的晶体中是沿晶轴a、b错开 ,上、下两层负离子配位多面体体呈交叉对应 ,从而达到稳定平衡。晶轴c与负离子配位多面体高次对称轴平行 ,配位多面体往界面叠合是绕着c轴转动的 ,其叠合轨迹为螺旋或同心环结构。从多型性晶体螺旋结构的规律性可以看出 ,晶体生长基元为负离子配位多面体 ,由于负离子配位多面体的面与呈现螺旋结构的晶面平行 ,所以生长速率慢 ,是一个显露面积大的稳态面。螺旋结构只是在该面族上显露。
In this paper, we discuss the formation of helical structure on the surface of polymorphic crystals by using the theory of anion coordination polyhedron growth primitives. It is proposed that the polyhedron is layered in the polytype crystal, the coordination polyhedron is the boundary of the layer, The underlying anion coordination polyhedron is not mirror-image symmetry, in the trigeminal and hexagonal crystal is along the crystal axis a, b staggered, the upper and lower two-tiered anion coordination polyhedron body cross, so as to achieve a stable equilibrium . The crystal axis c is parallel to the high-order symmetry axis of the coordination polyhedron of the ion-pair, and the coordination polyhedron is superposed on the c-axis to be superposed on the interface. The superposition trajectory is a spiral or concentric ring structure. As can be seen from the regularity of the polymorphic crystal helix structure, the crystal growth motif is an anionic coordination polyhedron. Since the plane of the anion coordination polyhedron is parallel to the crystal plane exhibiting a helical structure, the growth rate is slow and is a large exposed area Steady state surface. The spiral structure is revealed only on this surface race.