A compound made up of elements $\mathrm{A}$ and $\mathrm{B}$ (with a general formula ${\mathrm{A}}_{\mathrm{x}}{\mathrm{B}}_{\mathrm{y}}$), where $\mathrm{B}$ form a hcp lattice and A occupy$2/3^{\mathrm{rd}}$ of the tetrahedral voids. The formula of the compound is