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

这些图案组成的小块作晶胞，晶胞有不同的形状，如立方体和棱锥。

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

宝石学家通过在晶胞中指定三条轴来区分晶体。

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

们的共同点是缺乏对中心的晶胞。

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

通下， 这些偶极子会相互抵消，因此晶胞中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.

在大多数非压电晶体材料中，其晶胞中的原子围绕中心点对分布。

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.

如果晶轴之间长度相等且相互垂直，就像在一个立方体的晶胞中，那么当光穿过晶体，没有什么有趣的效应会发生。

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.

晶胞以同样的方法堆积起来，有时某种杂质物质将导致们在某个角度分开，或者使们更贴合于晶体的某一部分。