A first-principles investigation of the physical properties and radiation damage behavior of thorium-based compounds (ThX; X = C, N, P, As, Sb, O, S, Se)

This study establishes a comprehensive relationship between first-principles investigation of the structural, electronic, phonon spectrum, bonding, mechanical, and thermophysical property calculation and ion-implantation study of thorium-based compounds, ThX (X = C, N, P, As, O, S, Sb, Se). The DFT-based study reveals that the optimized lattice parameters show excellent agreement with available experimental and theoretical data, confirming the accuracy of the calculations. To predict the stability of the studied compounds, the formation energy has been calculated. Electronic band structure and density of states analyses reveal metallic behavior across the series. The Phonon dispersion curve confirms the dynamical stability of ThC, ThN, ThP, ThO, and ThS. Furthermore, bond population and charge density analyses indicate mixed ionic–covalent bonding, with covalent character most pronounced in ThC. Elastic constants satisfy the Born stability criteria, with all compounds exhibiting ductile behavior and varying degrees of elastic anisotropy. For the first time, the lattice thermal conductivity (using Slack’s equation) and diffusion thermal conductivity of the compounds have been evaluated. Thermophysical assessments identify ThN as the most promising candidate for high-temperature energy applications, exhibiting the highest Debye temperature (389.5 K), melting point (~2919 K), and lattice thermal conductivity (18.38 W m⁻¹ K⁻¹ at 300 K), alongside minimal thermal expansion. IRAD-based radiation damage analysis revealed that ThC and ThN exhibit deeper hydrogen penetration depths (~0.055 cm with ~0.015% atomic fraction and ~0.0015 DPA), accompanied by more uniformly distributed defect profiles. These results provide a unified dataset for ThX compounds, supporting materials selection for extreme-environment applications.