Abstract
A pressure-induced phase transition of Mg2Sr intermetallics from the low-pressure C14-type phase to an orthorhombic phase (space group Cmcm, Z = 4) at a high pressure of 21.0 GPa was firstly predicted using first-principles calculations combined with unbiased swarm structure searching techniques. The phase transition was identified as a first-order nature with a volume drop of 4.7%, driven by the softening of elastic behavior at high pressure. Further phonon calculations indicate that the newly predicted orthorhombic phase is dynamically stable at high pressure and ambient pressure. The mechanical properties including the elastic anisotropy of this orthorhombic phase were thus fully studied at ambient pressure. The elastic anisotropy behavior of this orthorhombic phase was investigated by the distributions of elastic moduli. The evidence of the bonding nature of Mg–Sr was also manifested by density of states (DOS) and electronic localization function (ELF) calculations.
Highlights
The study of Mg intermetallics has been attracting much attention because of their important applications in the automobile and aerospace industries [1,2]
In the Mg–Sr system is a typical Laves phase Mg2 Sr, the heat formation of which was firstly measured by King and Kleppa [14] by means of tin solution calorimetry
The heat formation of Mg2 Sr reported by Aljarrah and Medraj is in agreement with that of Yang et al [16], who investigated the elastic property and density of state (DOS) of this intermetallic phase
Summary
The study of Mg intermetallics has been attracting much attention because of their important applications in the automobile and aerospace industries [1,2]. Mg–Ba have been investigated for a long time, and different stable intermetallics have been found in these systems [5,6,7,8] Due to their importance, extensive studies have been undertaken of crystal structures and lattice parameters [9,10,11], as well as thermodynamic properties [12,13] for these. Aljarrah and Medraj [15] reoptimized the Mg–Sr system in the CALPHAD approach considering all the available experimental data on the phase diagram and provided the crystallographic data, heat formation, and lattice parameters of four intermetallic compounds (Mg2 Sr, Mg38 Sr9 , Mg23 Sr6 , and Mg17 Sr2 ). The heat formation of Mg2 Sr reported by Aljarrah and Medraj is in agreement with that of Yang et al [16], who investigated the elastic property and density of state (DOS) of this intermetallic phase
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