理论探索二维X_(2)UO_(4)(X=K,Rb,Cs)的力学特征、电子结构和声子输运特征

Theoretical investigation of the mechanical properties,electronic structure and phonon transport characteristics of 2D X_(2)UO_(4)(X=K,Rb,Cs)

本文用基于密度泛函理论的第一性原理计算方法,研究了三种建议的二维材料X_(2)UO_(4)(X=K,Rb,Cs)的稳定性、弹性、电子结构和声子振动特性.计算结果显示,三种材料同时具备较好的热力学、动力学和机械稳定性.电子结构表明,三种材料属于宽禁带间接半导体,其计算能隙分别是3.90、3.79和3.42 eV,并且在300 K时有着71.31-174.23 cm^(2)/Vs的电子迁移率.声子输运特性表明,三种材料的声子色散均没有虚频出现,声学模和低频光学模呈现强烈耦合,且有着低频率low-lying声子,这使得材料具备很强的声子非谐效应、低声子群速度和强声子散射率,从而表现出很低晶格热导率,在300 K温度下时仅为0.16-0.19 W/mK.这些特性表明,二维X_(2)UO_(4)(X=K,Rb,Cs)在纳米电子和热电器件领域具备应用潜力.

Based on the first principles of density functional theory,we proposed three novel two-dimensional materials,KU_(2)O_(4),RbU_(2)O_(4) and CsU_(2)O_(4),and further investigated their stabilities,elastic,electronic structure and phonon vibration characteristics.The calculation results show that the three 2D materials are wide-gap indirect semiconductors,with band-gaps of 3.90,3.79,and 3.42 eV,respectively,and deliver electron mobilities of 71.31~174.23 cm^(2)/Vs at 300 K.The phonon transport results show that all phonon dispersions have no virtual frequency,in which acoustic and low-frequency optical modes are strongly coupled,as well as low-frequencies for low-lying phonons,resulting in strong phonon-phonon anharmonic effect,low phonon group velocities and strong phonon scattering rates.As a result,they exhibit low lattice thermal conductivities of 0.16~0.19 W/mK at 300 K.All these properties indicate that 2D X_(2)UO_(4)(X=K,Rb,Cs)have high potential applications in the field of nanoelectronics and thermoelectric devices.