Abstract
The stability, mechanical properties and anisotropic properties of sound velocities of Ga2Mg5, GaMg2, GaMg, O-Ga2Mg, H-Ga2Mg and Ga5Mg2 are investigated systematically by the first-principles calculation. The cohesive energy and formation enthalpy are obtained and used to estimate the stability of the Ga-Mg binary compounds. GaMg compound is the most stable and has the lowest formation enthalpy as -0.162eV/atom of those GaxMgy compounds. The elastic constants of single crystal, hardness, bulk, shear, Young's modulus and Poisson's ratio of the polycrystalline crystal are obtained and used to estimate the mechanical properties. Ga5Mg2 and H-Ga2Mg have the lager bulk, shear and Young’s modulus and corresponding B/G is low. H-Ga2Mg is harder than the other compounds from the results of Poisson’s ratio. The anisotropic mechanical properties are discussed using the anisotropic index, two-dimensional planar projections on different planes of the bulk and Young's modulus. The Young's modulus of H-Ga2Mg shows the strongly anisotropy of mechanical properties and GaMg2 has the weakest anisotropy among all the compounds.
Highlights
Pure gallium is a soft metal with a low temperature melting point of 29.8 oC, in recent years, gallium is mainly used in liquid metal alloys with a variety of applications, including chip cooling[1,2,3,4], waste heat recovery5,6, electrical interconnects and contacts[7,8], biomedical equipment[9], kinetic energy harvesting[10], thermal interface material[11,12] or printed electronics[13,14,15,16]
The whole calculations are carried out by first principle calculations which are based on density functional theory (DFT) as implemented in Cambridge sequential total energy package (CASTEP) code[29,30,31]
The chemical stability, elastic properties, anisotropy of mechanical properties and anisotropic sound velocity of the Ga-Mg binary compounds have been investigated by first principles calculations
Summary
Pure gallium is a soft metal with a low temperature melting point of 29.8 oC, in recent years, gallium is mainly used in liquid metal alloys with a variety of applications, including chip cooling[1,2,3,4], waste heat recovery5,6 , electrical interconnects and contacts[7,8], biomedical equipment[9], kinetic energy harvesting[10], thermal interface material[11,12] or printed electronics[13,14,15,16]. Due to the particular characteristics of gallium, the addition of other elements to the gallium alloy will open up new possibilities for design and applications, such as magnesium. In Ga-Mg alloys, the effect of secondary phases (Mg5Ga2) and impurities on the localized corrosion mechanism using AFM/ SKPFM is studied[23]. The fundamental number of studies on Ga-Mg alloys is rather limited. Thermodynamics is the key component of Ga-Mg alloy, one of critically important thermodynamic data is the enthalpy of formation of the compounds, which can be obtained by first-principles calculations[28]
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