Crystal Structures

A crystal is formed by the infinite repetition of identical structural units in space. In the simplest crystals, the structural unit is a single atom. The structure of all crystals can be described in terms of a lattice, with a group of atoms attached to every lattice point. This group of atoms is referred to as the basis. The basis consists of a primitive cell, which contains a single lattice point. By arranging one cell at each lattice point, the entire crystal structure is built. There are several types of crystal structures, and the simplest are often used to illustrate this concept. A crystal family is defined by the combination of lattices and point groups and is formed by grouping crystal systems that share a common lattice system. In total, there are six crystal families: triclinic, monoclinic, orthorhombic, tetragonal, hexagonal and cubic.