Crystal structure

The ordered, three-dimensional arrangement of particles within a crystal is described using two linked ideas: the lattice and the basis. A lattice is a purely geometric arrangement of points repeating periodically in three dimensions, with no reference to what actual particle sits at each point; a crystal structure is generated by attaching one or more constituent particles -- the basis -- to every point of this lattice. In short, Lattice + Basis = Crystal: the lattice supplies the repeating geometric skeleton, and the basis supplies the physical particles that decorate every point of that skeleton to build the real crystal. This crystal lattice is also called the space lattice of the crystal. The following subsections build on this idea to define the unit cell -- the smallest repea …