准晶的故事*|

什么图形可以无缝隙的覆盖平面？限制在正多边形上就是：三角形、正方形、正六边形。

五边形就不可以。

旋转对称性只有 2,3,4,6 ，其它对称是不可能的。

Steinhardt 在 IBM 模拟金属原子时，发现很容易形成，它相当于三维空间的正五边形 平面密铺

数学	物理
	Haüy Traité de Minéralogie 1801

1. all pure substances form crystals, as long as there is enough time for the atoms and molecules to move into an orderly arrangement.
2. all crystals are periodic arrangements of atoms, meaning their structure is entirely composed of one of Haüy’s primitive building blocks, a single cluster of atoms that repeats over and over in any direction with equal spacing.
3. every periodic atomic arrangement can be categorized according to its symmetries and there is a finite number of possible symmetries.