The Investigation On Electronic Structure And Properties Of Actinide/Lanthanide Containing Layered Carbides

The ternary layered transition metal carbides and their two-dimensional(2D)derivatives(MXenes)have attracted increased attention due to their unique physiochemical properties and widespread potential applications.The ternary layered transition metal carbide has the metal-like electrical and thermal conductivity,and favorable machinability;and possesses the ceramic-like high temperature strength and excellent oxidation resistance.In addition,the previous studies have shown that the ternary layered carbide exhibits good radiation resistance.These excellent properties allow potential application of this type material in the field of nuclear energy.Due to the abundant elements,and versatile structures and properties,MXenes exhibit excellent performance inadsorbing radionuclides from nuclear waste treatment.Therefore,further exploration of new ternary layered structures and their 2D derivatives is of great significance.Currently,the layered transition metal carbides and theirderivative MXenes investigated are mainly restricted to those structures with early transition metals.The corresponding configurations with lanthanide or actinide metal are seldom reported.Based on first-principles density functional calculations,the electronic structures,dynamically stabilities and mechanical properties of the actinide-containing layered ternary carbides are investigated.According to the results,all the UAl₃C₃,U₂Al₃C₄,Pu Al₃C₃,Th Al₃C₃ and U₂CF₂ are determined to be dynamical stable,which provides new candidates for accident-tolerant nuclear fuel systems.Theoretical prediction of the thermal conductivity values of UAl₃C₃ and U₂Al₃C₄ at 1500K high temperature reached 23.1 and 22.9 w/(m·K),respectively.The carbon atom shows a strong interaction with uranium in the actinide-containing layeredternary carbides.UAl₃C₃ and U₂Al₃C₄are both metallic,and possess favorable mechanical properties.The stabilities,structural parameters and electronic properties of lanthanide-based MXenes,including the F and OH terminated,and bare configurations,are comprehensively investigated based on first-principles density functional calculations.To determine the stable functionalized structure,six possible configurations with functional groups on different sites are investigated.According to the theoretical calculation,the carbon-centered configuration is most stable for all the fluorine and hydroxyl functionalized configurations investigated.Most of the fluorine and hydroxyl functionalized MXenes except for La₂CT₂ and Lu₂CT₂(T=F,OH)are generally magnetic semiconductors with bandgap values in the range of 0.173 to 2.17e V.The room-temperature electron mobility in the zigzag direction and armchair direction of Lu₂C(OH)₂ is as high as 95.19×10³and 217.1×10³ cm² V^-1 s^-1,respectively.In addition,the211 MAX phase Lu₂AC(A=Al,Si and Sn)are investigated respectively.The results show that the elastic properties of these three Lu-based MAX phases are anisotropic,and the mechanical processing performance of Lu₂AlC is better than that of Lu₂SnC and Lu₂SiC.