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本文采用第一性原理和半经典玻尔兹曼理论相结合的方法研究了La_2CuBiS_5的基本性质.电荷差分密度图显示电子积聚在Bi-S原子之间,这意味着Bi和S之间成共价键.Cu和S之间的电荷差分密度与Bi-S的相似,表明Cu-S之间成共价键.计算表明La_2CuBiS_5的最小热导率非常小,这有利于材料的热电特性.受热激发引起的双极化效应的影响,材料的塞贝克系数在T=800 K时明显下降,n型和p型掺杂对应的最大S~2σ/τ值分别是-1.71×10~(11)和1.837×10~(11)WK~(-2)ms~(-1).沿Γ-Y方向上能带的大的弥散性和较高简并度有利于S_y和σ/τ_y.因此,La_2CuBiS_5展现出各向异性的热电特性,并且沿y方向上的热电特性最佳.
In this paper, the basic properties of La_2CuBiS_5 were studied by the combination of the first principle and the semi-classical Boltzmann theory.The charge-difference density diagram shows that the electrons accumulate between the Bi-S atoms, which means that Bi and S The difference in charge between Cu and S is similar to that of Bi-S, indicating a covalent bond between Cu and S. Calculations show that the minimum thermal conductivity of La 2 CuBiS 5 is very small, which is favorable for the thermoelectric properties of the material. The Seebeck coefficient of the material obviously decreases at T = 800 K, and the maximum S ~ 2σ / τ values corresponding to n-type and p-type doping are -1.71 × 10 ~ (11) And 1.837 × 10 ~ (11) WK ~ (-2) ms ~ (-1). The large dispersivity and high degeneracy of the band in the Γ-Y direction are in favor of S_y and σ / τ_y. Therefore, La 2 CuBiS_ 5 exhibits anisotropic thermoelectric properties and has the best thermoelectric properties along the y-direction.