The patterns form blocks called unit cells, which can be different shapes, like cubes or pyramids.

这些图案组成小块，有不同形状，如立方体和棱锥。

Geologists classify crystals by assigning three axes to the unit cell.

宝石学家通过在指定三条轴来区分体。

But what they all have in common is unit cells which lack a center of symmetry.

但它们共同点是缺乏对心。

Normally, these dipoles cancel each other out, so there's no net separation of charge in the unit cell.

通常情况下， 这些偶极子会相互抵消，因此不会出现净电荷分离。

In most non-piezoelectric crystalline materials, the atoms in their unit cells are distributed symmetrically around a central point.

在大多数非压电体材料，其原子围绕心点对分布。

If the axes are all the same length and at right angles to each other, like in a cubic unit cell, nothing very interesting will happen to the light passing through the crystal.

如果轴之间长度相等且相互垂直，就像在一个立方体，那么当光穿过体，没有什么有趣效应会发生。

The unit cells stack together in the same way, but sometimes an impurity will cause them to take off at an angle or make them more likely to stick to one part of the crystal than another.

以同样方法堆积起来，但有时某种杂质物质将导致它们在某个角度分开，或者使它们更贴合于体某一部分。