摘要:
运用以密度泛函理论为基础的相对论性离散变分方法(DV-Xα)模拟计算了完整的和含有F心、F~+心以及F_2心的碘化铯(CsI)晶体的电子结构,得到了含F心和F~+心以及F_2心的CsI晶体电子态密度分布以及它们可能产生的光学跃迁模式.计算结果表明,含F心和F~+心的CsI晶体的禁带宽度明显变窄,F心和F_2心的能级都出现在禁带中并且作为施主能级位于导带底部,利用过渡态理论计算得到其能级向Cs的5d轨道发生光学跃迁,能量跃迁值分别为1.69 eV和1.15 ev,该结果与实验结果完全一致,F~+心没有能级出现在禁带中.计算结果从理论上成功地解释了碘化铯晶体经过辐照后电子型色心所产生的吸收带起源问题.
Abstract:
The electronic structures of the perfect CsI crystal and the crystal containing iodine vacancy and F, F_2 color centers are studied within the framework of the fully relativistic self-consistent Dirac-Slater theory, by using a numerically discrete variational (DV-Xα) method. Calculated results reveal that the existence of the iodine vacancy results in the band gap widening and does not introduce the new energy level in the forbidden band. However, the crystal containing F color centers and F_2 color centers have their donor energy levels introduced in the forbidden band. The transition energy from energy level of F color center and F_2color center to the bottom of conduction band is 1.69 eV (736 nm) and 1.15 eV, respectively, which are consistent with the experimental results. This result indicates that the 750 nm absorption band originates from the F color center and the 1.1 eV absorption band originates from F_2 color center.
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