The College of Education for Pure Sciences, Department of Physics, University of Basra, discussed a master’s thesis entitled (Structural composition, thermoelectric properties and semi-metallic properties of X:Mg, K) XCaB (surface and boundary)
The thesis presented by the researcher (Wad Abdel Qader Abdel) included important clarifications about the electronic, magnetic and thermodynamic properties of the volumetric structures of the MgCaB and KCaB semi-Heussler compounds at the lattice equilibrium constant (6.27Ǻ) and (7.027Å), respectively, as well as the surfaces (001) and ( 111) for both compounds and the boundary MgCaB/AlSb (111), based on first-principles calculations and using generalized regression approximation (GGA), which is included within the DFT approximations.
In this work, the method of initial calculations based on the theory of functional density was used to study the properties of the volumetric and surface structure (111) and (001) of the two compounds MgCaB and KCaB, which are Half Heusler alloys, as well as the study of the interface between the compound MgCaB with AlSb surface ( 111), and this study included knowing the properties of semi-metallic materials, especially half-Heussler compounds, due to the importance of these materials, as they are considered as promising materials because of their importance in applications for twisting electronics devices.
We conclude that in the case of the volumetric structure, we noticed that both compounds exhibit the semi-metallic property with an energy gap of (0.74 eV) for MgCaB, while the energy gap of KCaB is (0.82 eV). The total magnetic moment of both compounds when the volumetric structure is equal to (B1μ). As for the surfaces (001) and (111), we noticed that they preserved the semi-metallic property at the Ca end only in both compounds, but at the rest of the ends the energy gap was broken. By studying the electronic and magnetic properties of the boundary of the compound MgCaB (111) with AlSb (111), it was found through the calculations that the forms Ca-Sb and Ca-Al have lost the semi-metallic character. In addition, we calculated the adhesion energies (γ) of the boundary and found that the form Ca-Sb is more stable than Ca-Al. We also note that the value of the magnetic moment of the Ca atom at the Ca-Al interface increases due to the large twisting decay of the density of the atomic states of the Ca atom, and we can notice the decrease in the magnetic moment of the Mg atom at the secondary interface in Ca-Al.
The study recommended that it is possible to study many other properties of the semi-Heussler alloys KCaB and MgcaB, including thermal conductivity, specific heat, elasticity, hardness and emissivity.....etc.
In order to be used in bromine electronics and materials engineering technology, we can also in the future study the different physical properties of alloys under certain external influences such as pressure and different temperatures.....etc.
