Design and characterization of structural, mechanical, electronic, and optical properties of Cr_xMo_1-xS₂ alloys for advanced material applications

This study presents a comprehensive analysis of the electronic, mechanical, and optical properties of Cr_xMo_1-xS₂, a bulk transition metal dichalcogenide. Using density functional theory with spin–orbit interaction, we employed both the generalized gradient approximation (GGA) and the modified Becke–Johnson potential (mBJ-GGA) to evaluate these properties. Our results confirm that all Cr_xMo_1-xS₂ alloys are nonmagnetic and thermodynamically stable, as evidenced by cohesive energy calculations. Mechanical assessments comply with Born’s criteria, further affirming their stability. Interestingly, lower concentrations of Cr, particularly in Cr_0.125Mo_0.875S₂, significantly enhance atomic bond strength and elastic stiffness. Additional mechanical analysis, including the universal elastic anisotropy index, microhardness, machinability index, and Pugh’s criterion, reveals that all alloys are anisotropic and brittle, with Cr_0.375Mo_0.625S₂ and Cr_0.625Mo_0.375S₂ demonstrating superior machinability. On the electronic front, the addition of Cr substantially modifies the MoS₂ bandgap and the density of states near the Fermi level. Even at low Cr concentrations, a significant reduction in the energy bandgap is observed, with notable contributions from Cr- \({d}_{{z}^{2}}\) $d_{z^2}$ orbitals to the valence and conduction bands. Optically, we examined the dielectric constant ε(ω) components, along with absorption (α(ω)), reflection (R(ω)), and refraction (n(ω)) coefficients in both X and Z directions. An increase in Cr concentration leads to a redshift in these properties, with prominent peaks in the visible light spectrum, especially in the yellow and blue light energies. The thorough examination of electronic, mechanical, and optical properties suggests that Cr_xMo_1-xS₂ alloys hold significant potential for various applications in electronic and optical technologies, particularly in areas requiring bandgap engineering.