Aluminium Nitride Structure

Aluminium nitride (AlN) is a covalently bonded material that crystallizes in the wurtzite crystal structure. The wurtzite structure belongs to the hexagonal crystal system, and it consists of two interpenetrating triangular lattices.

The AlN unit cell contains two atoms: one aluminum atom at the lattice site (0,0,0), and one nitrogen atom at the lattice site (1/3, 2/3, 3/4). The lattice parameters for AlN are a = b = 3.112 Å and c = 4.979 Å.

In the wurtzite structure, each aluminum atom is surrounded by four nitrogen atoms arranged in a tetrahedral configuration, and each nitrogen atom is surrounded by four aluminum atoms arranged in a tetrahedral configuration as well. This results in a three-dimensional network of covalent bonds between the aluminum and nitrogen atoms.

The wurtzite structure also exhibits polarity due to the asymmetric arrangement of the atomic positions along the c-axis. The aluminum ions are located closer to the base of the unit cell, while the nitrogen ions are located closer to the apex. This creates a dipole moment along the c-axis, which can affect the electrical and optical properties of the material.

Overall, the wurtzite structure of AlN is important for its unique properties, such as its high thermal conductivity, high hardness, and excellent dielectric properties. It also has potential applications in optoelectronics, microelectronics, and power electronics due to its wide bandgap energy and high breakdown voltage.