Abstract:
Self-consistent electronic structure calculations have been performed on ordered
cubic-based magnesium-lithium (Mgx-Li1−x) alloys spanning the concentration range
0 ≤ x ≤ 1, using an ab initio plane wave pseudopotential (PWP) method. The first
principle pseudopotential planewave approach is used within the local density approximation
(LDA) and generalized-gradient approximation (GGA)of the density functional
theory (DFT) framework. We have calculated the binding energy curves and the systematic
trends in various cohesive and elastic properties at zero temperature, as a function
of Li concentration. The calculated equilibrium lattice parameters show a large
deviation from Vegard’s rule in the Li-rich region whilst the bulk moduli decrease
monotonically with increase in Li concentration. The heats of formation for different
ground state superstructures predict that the DO3, B2 and DO22 structures would
be the most stable at absolute zero amongst various phases having the Mg3Li, MgLi
and MgLi3 compositions, respectively. This stability is reflected in the electronic density
of states (DOS). Because of the special significance of the isotropic bulk modulus,
shear modulus, Young’s modulus and Poisson’s ratio for technological and engineering
applications, we have also calculated these quantities from the elastic constants.
The elastic constants indicate the softness of the material as more Li is added with
the bcc-based phases becoming mechanically less stable for Li concentration less than
50%. Our results show good agreement within the estimated uncertainty with both
experimental and previous theoretical results.
