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This study explored the physical properties of MAX phase borides, M2GaB (M = Sc, V, Nb, Ta), aided by the density functional theory (DFT) for the first time. The optimized lattice constants were obtained by minimizing the total energy. We checked the thermodynamic stability by computing the formation energies. We calculated the electronic band structure, density of states (DOS), and charge density mapping to reveal the electronic ground state and bonding nature. The computed stiffness constants (Cij) confirmed the mechanical stability of the investigated compounds. Young's modulus, shear modulus, bulk modulus, and Poison's ratio have been computed using Cij. We calculated the Pugh's ratio, Poisson's ratio, and Cauchy pressure to judge the ductility/brittleness. The Vickers hardness values were calculated. The anisotropic properties of M2GaB compounds were studied by the elastic moduli's directional projections and the anisotropy indices' calculations. We have discussed the acoustic behavior of the M2GaB phases. We have also investigated the Grüneisen parameter, the Debye temperature ϴD, the thermal expansion coefficient, the specific heat, the Helmholtz free energy, the entropy, the internal energy, and the lattice thermal conductivity (Kph) of these borides. To determine the suitability as thermal barrier coating (TBC) materials or whether the compounds are appropriate for high-temperature applications, the minimum thermal conductivity (Kmin) and melting temperature (Tm) have also been calculated. The compounds' dynamical stability was examined using the phonon dispersion curves. The optical parameters have been studied, and it has been found that these compounds are compatible as coating materials to reduce solar heating.

In this paper, a first-principles study of the newly known MAX phase borides Zr2AB2 (A = In, Tl) has been carried out. The stiffness constants, elastic moduli, mechanical anisotropy, thermal and optical properties are investigated for the first time. The structural lattice parameters are found to be consistent with previous study. The dynamical and mechanical stability of the titled compounds have been checked. Fundamental insights into the stiffness constants, elastic moduli, hardness parameters, brittleness and anisotropy indices are presented. The variation of these mechanical properties is explained based on the Mulliken population analysis and charge density mapping (CDM). The metallic nature and anisotropy in conductivity has been confirmed from the electronic band structure. The analysis of DOS revealed the dominant contribution from Zr-d orbitals to the conductivity. The higher values of ΘD and Tm, and lower value of Kmin for Zr2AB2 (A = In, Tl) compared to those of Zr2AC (A = In, Tl) suggest enhanced thermal properties of the compounds under study for practical applications. Besides, the specific heat capacities (Cv, Cp), thermal expansion coefficient, and different thermodynamic potential functions have been calculated. The technologically important optical constants have been studied with an intention to reveal their possible relevance for application purposes. The reflectivity spectra revealed the applicability of Zr2AB2 (A = In, Tl) as cover materials to diminish the solar heating. The studied physical properties of Zr2AB2 (A = In, Tl) are compared with those of other relevant 212 and 211 MAX phase nanolaminates.

In this article, a detailed study of the recently synthesized MAX phase borides M2SB (M = Zr, Hf and Nb) has been performed via first principles technique. Investigation of mechanical properties, elastic anisotropy, optical properties, dynamical stability and thermal properties are considered for the first time. The estimated values of stiffness constants and elastic moduli are found in good agreement with available results. The Vickers hardness is also calculated using Mulliken population analysis. The electronic density of states and charge density mapping are used to explain the variation of stiffness constants, elastic moduli and hardness parameters among the studied ternary borides. The Nb2SB compound is found to show the best combination of mechanical properties. Mixture of covalent and ionic bonding within these borides is explained using Mulliken population analysis. The direction dependent values of Young's modulus, compressibility, shear modulus and Poisson's ratio are visualized by 2D and 3D representations and different anisotropic factors are calculated. The important optical constants are calculated and analyzed. The metallic nature of the studied borides is confirmed from the density of states (DOS) and optical properties. The reflectivity spectra reveal the potential use of Zr2SB as coating materials to diminish solar heating. The studied borides are dynamically stable as confirmed from the phonon dispersion curves. The characteristic thermodynamic properties have also been calculated and analyzed. The physical properties of corresponding 211 MAX phase carbides are also calculated for comparison with those of the titled ternary borides.

The thermodynamic, dynamic, and mechanical stabilies of newly proposed 211 MAX phase borides, M 2 CuB (M = Zr, Mo, and W), was investigated. This exploration involved calculating formation energies, examining phonon dispersion curves, and analyzing elastic constants using first principle calculations. Electronic band structures and density of states were determined, revealing the metallic nature of these compounds. The study delved into Young's modulus and linear compressibility (β) values, visually represented in 2D and 3D formats, indicating anisotropy within the (x - z) plane for all investigated MAX phases. Moreover, all compounds exhibited ductility according to Vickers hardness calculations. Employing Slack's model, lattice thermal conductivity was predicted, suggesting these MAX phases as promising candidates for thermal barrier coating applications. Various thermal parameters, including Debye temperature, melting temperature, and minimum thermal conductivity, were employed to assess the thermal properties of these materials. Additionally, the study explored the optical properties, leading to discussions on potential applications for the studied MAX phases. [Display omitted] • Investigated stability of three new 211 MAX phases borides: M 2 CuB (M = Zr, Mo, and W). • Demonstrated stability through formation energies, phonon dispersion, and elastic constants. • Identified ductile nature in all three borides: M 2 CuB (M = Zr, Mo, and W). • Predicted lattice thermal conductivity, indicating potential thermal barrier coating (TBC) applications [ABSTRACT FROM AUTHOR]

• Physical properties of Hf 2 AB 2 (A = In, Sn) have been studied using first-principles technique. • Hf 2 AB 2 (A = In, Sn) compounds have higher mechanical strength and Vickers hardness compared to those of Hf 2 AC (A = In, Sn). • The charge density mapping discloses the existence of very strong B‒B covalent bonds in Hf 2 AB 2 (A = In, Sn). • Hf 2 AB 2 (A = In, Sn) have superior thermal properties compared to Hf 2 AC (A = In, Sn). • Hf 2 AB 2 (A = In, Sn) has the potential to be used as reflecting coating to diminish solar heating. ga1 212 MAX phase borides are new additions to the MAX phase family with enhanced thermo-mechanical properties. In this article, first-principles calculations have been carried out to explore the mechanical properties, Vickers hardness, elastic anisotropy, thermal properties, and optical properties of predicted thermodynamically stable MAX compounds Hf 2 AB 2 (A = In, Sn). The structural properties are compared with the available data to assess the validity of calculations. The mechanical stability of Hf 2 AB 2 (A = In, Sn) compounds is established with the help of the computed stiffness constants (C ij). The possible reason for enhanced mechanical properties and Vickers hardness of Hf 2 SnB 2 is explained based on the analysis of bonding strength, followed by the electronic density of states. Higher mechanical strength and Vickers hardness of Hf 2 AB 2 (A = In, Sn) compared to Hf 2 AC (A = In, Sn) are also indicated in the light of charge density mapping. The values of Pugh ratio, Poisson's ratio and Cauchy pressure predict brittle character of the studied compounds. Besides, the anisotropic nature of the titled borides is investigated by 2D and 3D plots of elastic moduli along with some well established anisotropy indices. Thermal properties were investigated by calculating the Debye temperature, minimum thermal conductivity, Grüneisen parameter, and melting temperature. The thermal properties of Hf 2 AB 2 (A = In, Sn) are also superior to Hf 2 AC (A = In, Sn). The optical constants such as real and imaginary parts of the dielectric function, refractive index, extinction coefficient, absorption coefficient, photoconductivity, reflectivity, and loss function are investigated. [ABSTRACT FROM AUTHOR]