Ψ Ψ is a complex number of magnitude | Ψ Ψ ( r → → ) | ≤ ≤ 1 and the orientation of the six-folded director is given by the phase. In a hexagonal crystal, this is nothing else but the crystal-axes. The local director field disappears for a particle with five or seven nearest neighbours, as given by dislocations and disclinations Ψ Ψ ∼ ∼ 0 , except a small contribution due to thermal motion. The orientational correlation function between two particles i and k at distance r → → = r → → i − − r → → k is now defined using the local director field: