非完整形态KH2PO4晶体薄表面层生长特性

实时观察了非完整形态的KH2PO4 (KDP)晶体在过饱和溶液中以薄表面层生长形式恢复其结晶学形态的过程.提出了晶体形态恢复的“最小多面体原理”,即:在自由生长系统中,对于非完整形态的KDP晶体,当其以薄表面层形式恢复其结晶学完整形态时,薄表面层将选择相应的奇异面方向生长,使晶体形态最终恢复为一个由各结晶学显露面所围成的体积最小的凸多面体.利用PBC理论分析了生长基元在非结晶学显露面上的附着情况并阐述了锥顶处薄表面层倒垂生长的原因.结果表明,薄表面层形成与晶体非完整结晶学形态及不均匀水动力学条件相关联.柱面凹角与非正常棱边及Z切片正常棱角均可诱发产生薄表面层,且薄表面层生长终止于其所在奇异面的正常结晶学晶棱.

Growth Habit of Thin Surface Layer of KH2PO4 Crystal with Incomplete Crystallographic Shape

The regeneration process of KH2PO4 (KDP) crystal faces of incomplete crystallographic shape by means of the growth of thin surface layers in supersaturated solution was observed."The smallest convex polyhedron principle" was put forward as a principle of crystallographic shape recovery.The principle refers to that when a KDP crystal of incomplete crystallographic shape recovers its crystallographic shape in a free crystal growth system by thin surface layer growing along the corresponding appearing faces,its geometric shape is approximate to a convex polyhedron of the smallest volume which is bounded by the appearing faces of the crystal.In addition,the attachment of growth unit to the positions of crystal disappearing face was investigated with the principle of PBC (periodic bond chain) theory which has been used for explain the formation of the new thin {101} layers generated from apexes.The results show that the thin surface layers,which are closely related to the incomplete crystallographic shape of crystal itself and the inhomogeneous hydrodynamic condition,will generate from both the concave corners and the abnormal edges of incomplete prismatic faces and the normal angles of Z-cut plates,and end at the normal crystallographic edges of the corresponding singular surface.