Structural and anisotropic elastic properties of Zintl M2Pb (M = Ca, Sr and Ba) compounds as a function of pressure

By means of first-principles calculations within the generalized gradient approximation, the structural properties, phase stabilities and anisotropic elastic properties of binary Zintl compounds Ca2Pb, Sr2Pb and Ba2Pb as a function of pressure have been investigated. Results of formation enthalpies show that they are energetically stable at ground state, and the stability of Ca2Pb is better with the increasing pressure. Based on the calculated elastic constants C-ij, elastic properties, including bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratios nu, were evaluated by the use of Voigt-Reuss-Hill (VRH) approximation. The mechanical anisotropies were characterized by several anisotropic indexes and three-dimensional surface construction, and the results indicate that these Zintl compounds exhibit anisotropic mechanical properties. Finally, the Debye temperatures and sound velocities along [100], [010] and [001] directions under high pressure were also calculated. (C) 2014 Elsevier B.V. All rights reserved.