First-principles calculations on structural and electronic properties of Al18Mg3M2 phases (M = Sc, Ti, Cr, Mn and Zr)

The plane-wave ultrasoft pseudopotential method based on the density-functional theory has been used to calculate the crystal, electronic structures and the stability of Al18Mg3M2 (M = Sc, Ti, Cr, Mn and Zr) compounds with cubic structure. The calculated results show that stability of Al18Mg3M2 componds decreases in the order Al18Mg3Mn2 < Al18Mg3Cr2 < Al18Mg3Ti2 < Al18Mg3Sc2 < Al18Mg3Zr2. The density of states and charge density analyses show that the bondings of Al18Mg3M2 compounds have both covalent and ionic properties and the all crystals exhibit a metallic feature. The bonding nature of Al18Mg3M2 compounds is investigated, showing stronger covalent bonding between transition metal atoms and Al than between Al and Al, between Mg and Al.