A first-principles study of the mechanical and thermodynamic properties of WTi, WV, W2Zr, WVTi, WVZr alloys

Determination of the site preference on the structure, magnetism and mechanical anisotropy properties of Mo-containing alloy carbide M6C (MFe, Mo)

First-principles calculations are used to study the structure, magnetism and mechanical anisotropy properties of M₆C (M = Fe, Mo) carbides. The stability of alloy carbide M₆C can be improved when Mo atoms occupy the 48f Wyckoff position. Fe₃Mo₃C with Mo atoms occupying 48f position and Fe atoms occupying 16d and 32e positions has the best structural stability. The magnetic moment is triggered when the Fe content is approximately 0.5, suggesting that there exists a critical value between the paramagnetic nature and ferromagnetism. Carbides with Fe content above 0.5 have stronger magnetism. Higher Fe content corresponds to the stronger chemical bonding of carbides, resulting in improved elastic properties when Mo atoms are held in 48f position. The special carbides Fe₄Mo₂C and Fe₃Mo₃C (Fe at 48f site, Mo at 16d and 32e sites) correspond to the excellent mechanical properties. These results are helpful in providing a theoretical foundation of the possible direction for the advances of the excellent physical properties in Mo-containing steel.

Theoretical Screening of Transition Metal Doped Defective MoS2 as Efficient Electrocatalyst for CO Conversion to CH4

CO is a key intermediate during electrochemical CO₂ conversion. The deep reduction of CO to value-added chemical products is a crucial strategy for effective carbon utilization. Single transition metal atoms supported by two-dimensional material present a novel paragon for various catalytic reactions. Herein, we employ first principle theory to study a series of single 3d-transition metal atoms supported by monolayered MoS₂ with S vacancy as efficient electrocatalyst for CO electroreduction to CH₄ . The screening result indicates that Cr doped defective MoS₂ (labeled as Cr/S_v -MoS₂ ) is beneficial to electroreduction of CO to CH₄ , with even less negative limiting potential (-0.32 V) than Cu that has been widely studied as the most promising electrocatalyst in experiment. The outstanding activity is derived from the regulation of the d-band-center of doped Cr and Mo atoms exposed on the surface. This discovery provides a theoretical basis for the preparation of future electrocatalysts for CORR.