Newly synthesized MAX phase Zr2SeC: DFT insights into physical properties towards possible applications

DFT Insights into MAX Phase Borides Hf2AB [A = S, Se, Te] in Comparison with MAX Phase Carbides Hf2AC [A = S, Se, Te]

In this work, density functional theory (DFT)-based calculations were performed to compute the physical properties (structural stability, mechanical behavior, and electronic, thermodynamic, and optical properties) of synthesized MAX phases Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, and Hf2TeB and the as-yet-undiscovered MAX carbide phase Hf2TeC. Calculations of formation energy, phonon dispersion curves, and elastic constants confirmed the stability of the aforementioned compounds, including the predicted Hf2TeC. The obtained values of lattice parameters, elastic constants, and elastic moduli of Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, and Hf2TeB showed fair agreement with earlier studies, whereas the values of the aforementioned parameters for the predicted Hf2TeC exhibit a good consequence of B replacement by C. The anisotropic mechanical properties are exhibited by the considered MAX phases. The metallic nature and its anisotropic behavior were revealed by the electronic band structure and density of states. The analysis of the thermal properties-Debye temperature, melting temperature, minimum thermal conductivity, and Grüneisen parameter-confirmed that the carbide phases were more suited than the boride phases considered herein. The MAX phase's response to incoming photons further demonstrated that they were metallic. Their suitability for use as coating materials to prevent solar heating was demonstrated by the reflectivity spectra. Additionally, this study demonstrated the impact of B replacing C in the MAX phases.

Structural, Electronic, and Mechanical Properties of Zr2SeB and Zr2SeN from First-Principle Investigations

MAX phases have exhibited diverse physical properties, inspiring their promising applications in several important research fields. The introduction of a chalcogen atom into a phase of MAX has further facilitated the modulation of their physical properties and the extension of MAX family diversity. The physical characteristics of the novel chalcogen-containing MAX 211 phase Zr2SeB and Zr2SeN have been systematically investigated. The present investigation is conducted from a multi-faceted perspective that encompasses the stability, electronic structure, and mechanical properties of the system, via the employment of the first-principles density functional theory methodology. By replacing C with B/N in the chalcogen-containing MAX phase, it has been shown that their corresponding mechanical properties are appropriately tuned, which may offer a way to design novel MAX phase materials with enriched properties. In order to assess the dynamical and mechanical stability of the systems under investigation, a thorough evaluation has been carried out based on the analysis of phonon dispersions and elastic constants conditions. The predicted results reveal a strong interaction between zirconium and boron or nitrogen within the structures of Zr2SeB and Zr2SeN. The calculated band structures and electronic density of states for Zr2SeB and Zr2SeN demonstrate their metallic nature and anisotropic conductivity. The theoretically estimated Pugh and Poisson ratios imply that these phases are characterized by brittleness.

Overview of structural, electronic, elastic, thermal, optical, and nuclear properties of Zr2AC (A= Al, Si, P, S, Ge, As, Se In, Sn, Tl, and Pb) MAX phases: A brief review

The Zr2AC MAX phases are a family of ternary carbides ceramics that possess layered structures and exhibiting exceptional properties resulting from combining the most desirable features of metals and ceramics. In addition, the Zr2AC MAX-phases exhibit numerous physical and chemical properties due to their chemical and structural characteristics, a tendency for multiple basal dislocations and exhibiting mobility under ambient conditions. This review extensively analyzes the properties of the Zr2AC MAX phase, as they are closely linked to the exceptional and potential applications of the MAX phase. For the first time, the present study analyzed various properties of Zr2AC MAX phases, including structural, electronic, elastic, thermal, optical, self-healing, nuclear, oxidation, and corrosion characteristics. Furthermore, this review included experimental and theoretical work with comparison. It's found that the Zr2AC lattice parameters a and c are deviations theoretically from 0.1 to 2% and 0.15-2.87% compared with experimental work. Also, the Zr2AC MAX phases are metallic characters and the conductivity differs depending on the type of the Zr2AC(different A element) MAX phases. Its concluded that the Zr2AC MAX phases are stiff, isotropic elastic properties and high machinability with damage tolerance and hardness levels ranging from 3.5 to 13.02 Gpa. The Zr2AC MAX phases are also resistant to corrosion, thermal shock, and oxidation as well as lightweight. In addition, at elevated temperatures the transition from brittle to plastic behavior can be occurred in the Zr2AC MAX phase. The Zr2AC MAX phase's optical properties are anisotropic such as electrical conductivity and mechanical properties. This review study provides a comprehensive details assisting researches to deal with Zr2AC MAX phase potentially for different applications.

DFT insights into Nb-based 211 MAX phase carbides: Nb2AC (A = Ga, Ge, Tl, Zn, P, In, and Cd)

In this study, we performed the first-principles calculations to study the 211 MAX phase carbides: Nb₂AC (A = Ga, Ge, Tl, Zn, P, In, Cd, and Al). The structural characteristics are in good agreement with those of the prior studies. The mechanical behavior has been explored by calculating the stiffness constants, elastic moduli, and Vickers hardness. The stiffness constants and phonon dispersion curves were used to check the structural stability of the selected compounds. 2D and 3D plotting of elastic moduli and calculated anisotropy indices disclosed the anisotropy of the elastic properties. We utilized the Mulliken atomic and bond overlap population to explain the mixture of ionic and covalent bonding among these carbides. The metallic behavior has been confirmed by calculating the band structure and density of states (DOS). Partial DOS was also used to discuss the bonding nature and strength among the different states. The optical properties of these phases have also been computed and analyzed to reveal possible relevance in diverse fields. The Debye temperature (Θ _D), Grüneisen parameter (γ), melting temperature (T _m), and minimum thermal conductivity (K _min) were studied to bring out their possible relevance in high-temperature technology. The outcomes of this research indicate that the titled carbides are suitable for use as solar radiation-protecting coating and thermal barrier coating (TBC) materials.

The Rise of 212 MAX Phase Borides: DFT Insights into the Physical Properties of Ti2PB2, Zr2PbB2, and Nb2AB2 [A = P, S] for Thermomechanical Applications

In this article, ab initio calculations of unexplored Ti₂PB₂, Zr₂PbB₂, and Nb₂AB₂ [A = P, S] were performed wherein Ti₂PB₂ along with its 211 boride phase Ti₂PB was predicted for the first time. The stability was confirmed by calculating the formation energy, phonon dispersion curve, and elastic stiffness constants. The obtained elastic constants, elastic moduli, and Vickers hardness values of Ti₂PB₂, Zr₂PbB₂, and Nb₂AB₂ [A = P, S] were found to be significantly larger than those of their counterparts 211 borides and carbides. The studied compounds are brittle, like most MAX and MAB phases. The electronic band structure and density of states revealed the metallic nature of the titled borides. Several thermal parameters were explored, certifying the suitability of Ti₂PB₂, Zr₂PbB₂, and Nb₂AB₂ [A = P, S] to be used as efficient thermal barrier coating materials. The response of Ti₂PB₂, Zr₂PbB₂, and Nb₂AB₂ [A = P, S] to the incident photon was studied by computing the dielectric constant (real and imaginary parts), refractive index, absorption coefficient, photoconductivity, reflectivity, and energy loss function. In this work, we have explored the physical basis of the improved thermomechanical properties of 212 MAX phase borides compared to their existing carbide and boride counterparts.

Exploration of the physical properties of the newly synthesized kagome superconductor LaIr3Ga2 using different exchange-correlation functionals

LaIr₃Ga₂ is a kagome superconductor with a superconducting temperature (T_c) of 5.16 K. Here, we present the physical properties of the LaIr₃Ga₂ kagome superconductor computed via the DFT method wherein six different exchange-correlation functionals were used. The lattice parameters obtained using different functionals are reasonable, with a slight variation compared to experimental values. The bonding nature was explored. The elastic constants (C_ij), moduli (B, G, Y), and Vickers hardness (H_v) were computed to disclose the mechanical behavior. The H_v values were estimated to be 2.56-3.16 GPa using various exchange-correlation functionals, indicating the softness of the kagome material. The Pugh ratio, Poisson's ratio, and Cauchy pressure revealed the ductile nature. In addition, mechanical stability was ensured based on the estimated elastic constants. The anisotropic mechanical behavior was confirmed via different anisotropic indices. The Debye temperature (Θ_D), melting temperature (T_m), and minimum thermal conductivity (k_min) were calculated to characterize the thermal properties and predict the potential of LaIr₃Ga₂ as a thermal barrier coating material. The electronic density of states was investigated in detail. The McMillan equation was used to estimate T_c, and the electron-phonon coupling constant (λ) was calculated to explore the superconducting nature. The important optical constants were also calculated to explore its possible optoelectronic applications. The values of reflectivity in the IR-visible region are about 62% to 80%, indicating that the compound under study is suitable as a coating to reduce solar heating. The obtained parameters were compared with previously reported parameters, where available.