Theoretical investigations on structural and thermo-mechanical properties of layered ternary carbide Th–Al–C systems

Abstract With the concept of accident tolerant fuel systems being proposed, the new generation of nuclear fuels have attracted wide attention. In this work, a novel type of layered ternary carbides Th–Al–C are found by first-principles calculations via the density functional theory and the structures, electronic structures, thermal and mechanical properties are predicted. The calculation results show that all the Th–Al–C materials inspected are elastically and dynamically stable. From the decomposition reaction analysis, the ThAl3C3 phase is thermodynamically stable and Th2Al3C4 might also be obtained in the laboratory. These compounds have good elastic moduli and thermal properties. Th2AlC is a ductile material whereas others are brittle. The shear modulus and Debye temperature of Th–Al–C series decreases as the thickness of Th–C or Al–C slabs increases. The lattice thermal conductivity of the Th–Al–C system increases in the sequence of Th3Al4C6, Th2AlC, Th2Al3C5, Th2Al4C5, Th3Al3C5, Th4Al3C6, Th2Al3C4 and ThAl3C3. Moreover, both the ThAl3C3 and Th2Al3C4 not only have satisfactory mechanical properties, but also exhibit excellent thermal properties, which are comparable to those of Zr/Hf–Al–C compounds. The current theoretical investigations may promote the exploration of the novel layered ternary actinide carbides and may provide a new clue for finding high performance nuclear fuels.