Enhancing structural stability and mechanical performance of Pmmn-phase U2Mo alloy through V and Ti Doping: Insights from density functional theory

Abstract

Given the urgent demand for high-performance nuclear fuels driven by advanced reactor technologies, in-depth investigations into uranium-based alloys have garnered significant attention. This study employs density functional theory (DFT) to systematically investigate the effects of vanadium (V) and titanium (Ti) doping on the structural stability, electronic properties, mechanical characteristics, and thermodynamic behaviors of Pmmn-phase U2Mo alloys. Through structural optimization and phonon spectrum analysis, dynamically stable doped configurations were successfully constructed. These doped systems exhibit enhanced thermodynamic stability compared to the pristine U4Mo2 matrix. Density of states (DOS) analysis reveals intensified hybridization of V-4d orbitals above the Fermi level. Mechanically, U4VMo demonstrates substantial improvements, including enhanced shear modulus (G) and Young's modulus (E), along with an 11 % increase in tensile strength along the [100] crystallographic direction. Thermodynamic evaluations underscore superior high temperature performance, with U4MoTi displaying an increase in thermal expansion coefficient at 950 K relative to the matrix. Volumetric expansion analysis identifies lattice distortion relaxation induced by Ti/V doping, resulting in a 15–18 % elevation in ΔL/L₀ ratios. These findings establish a theoretical foundation for optimizing uranium-molybdenum nuclear fuels through transition metal doping, offering critical insights for advanced nuclear fuel design and application.