principal crystallographic axis

例句：

1. 1.The principal crystallographic axis of the crystal is perpendicular to the plane of the crystal.
   晶体的主要晶轴垂直于晶体的平面。
2. 2. The crystal structure of this compound is determined by the principal crystallographic axis.
   这种化合物的晶体结构由主要晶轴确定。
3. 3. During the growth process, the crystals are aligned along the principal crystallographic axis.
   在生长过程中，晶体沿着主要晶轴排列。