钆掺杂La_(2)Ce_(2)O_(7)电子结构和性能的第一性原理计算

First-Principles Calculation of Electronic Structure and Properties of Gd Doped La_(2)Ce_(2)O_(7)

利用基于密度泛函理论的第一性原理计算方法,研究了不同钆掺杂量(La_(1−x)Gd_(x))_(2)Ce_(2)O_(7)(x为物质的量分数,取0,0.25,0.50,0.75,1.00)的几何结构、电子结构、力学和热学性能。结果表明:(La_(1−x)Gdx)_(2)Ce_(2)O_(7)能带结构为Γ-X间接带隙,带隙随着x的增加而减小;随着x的增加,(La_(1−x)Gdx)_(2)Ce_(2)O_(7)的晶格常数和体积先减小后增大,相对分子质量增大,密度先增大后减小;(La_(1−x)Gdx)_(2)Ce_(2)O_(7)的力学性能均符合Born-Huang稳定性判据,说明(La_(1−x)Gdx)_(2)Ce_(2)O_(7)具有良好的力学稳定性;Pugh比(剪切模量与体模量之比)小于0.571,泊松比大于0.26,说明(La_(1−x)Gdx)_(2)Ce_(2)O_(7)具有良好的韧性,具备承受热循环应力的能力;(La_(1−x)Gdx)_(2)Ce_(2)O_(7)的最小热导率在0.98~1.26 W·m^(−1)·K^(−1)之间,低于氧化钇稳定氧化锆,表明(La_(1−x)Gdx)_(2)Ce_(2)O_(7)具有良好的热学性能,可以作为热障涂层的候选材料。

The geometric structure,electronic structure and mechanical and thermal properties of(La_(1−x)Gdx)_(2)Ce_(2)O_(7)(x was mole fraction with values of 0,0.25,0.50,0.75 and 1.00)were studied with different Gd doping amounts by firstprinciples calculation based on density functional theory.The results show that the band structure of(La_(1−x)Gdx)_(2)Ce_(2)O_(7)wasΓ-X indirect band gap,and the band gap decreased with the increase of x.With the increase of x,the lattice constant and volume of(La_(1−x)Gdx)_(2)Ce_(2)O_(7)first decreased and then increased,the relative molecular mass increased,and the density first increased and then decreased.The mechanical properties of(La_(1−x)Gdx)_(2)Ce_(2)O_(7)all agreed with the Born-Huang stability criterion,indicating that(La_(1−x)Gdx)_(2)Ce_(2)O_(7)had good mechanical stability.The Pugh's ratio(ratio of shear modulus to bulk modulus)was less than 0.571,and the Poisson's ratio was greater than 0.26,indicating that(La_(1−x)Gdx)_(2)Ce_(2)O_(7)had good toughness and could withstand thermal cycling stress.The minimum thermal conductivity of(La_(1−x)Gdx)_(2)Ce_(2)O_(7)ranged from 0.98 W·m^(−1)·K^(−1)to 1.26 W·m^(−1)·K^(−1),which was lower than that of yttria-stabilized zirconia,indicating that(La_(1−x)Gdx)_(2)Ce_(2)O_(7)had good thermal properties and could be used as a candidate material for thermal barrier coatings.