Elastic properties of MgxTi1-xB2(0 ≤ x ≤ 1) studied by first-principles calculations

The elastic properties, including elastic constants, bulk, and shear moduli, and anisotropic index of hexagonal MgxTi1-xB2 (0 <= x <= 1) are obtained using a first-principles density-functional-theory method. A difference in chemical bonding occurs between Ti-rich and Mg-rich diborides, leading to significantly different elastic properties: a small elastic anisotropy with relatively large bulk and shear moduli for Ti-rich diborides with x < 0.25, and a large elastic anisotropy and relatively small bulk and shear moduli for Mg-rich diborides with x > 0.25. The calculated results reveal a dominant role of the interplanar metal-metal bonds in predicting the extent of shear elastic anisotropy in MgxTi1-xB2 (0 <= x <= 1).