CuI晶体及其缺陷态电子结构的模拟

利用相对论密度泛函理论和嵌入分子团簇方法,模拟计算了具有闪锌矿结构的γ态CuI晶体及其缺陷态的电子结构。结果显示晶体的本征能级结构:价带顶主要由I5p和Cu3d轨道杂化组成,导带底由Cu4s轨道组成,禁带宽度为3.1eV,该结果与实验相符。在不同缺陷态的计算中,四面体间隙铜缺陷相对其他间隙缺陷更易于在晶体中形成,其中Cu3d→4s跃迁能量为3.2eV,推测与CuI晶体发光密切相关。

Simulation of Electronic Structures of CuI Crystal and Its Point Defects

The electronic structures of copper iodide crystal in γ phase and point defects associated with iodine and copper have been studied with relativistic density functional theory and embedded cluster method(DVM).Through the electronic densities of states of copper iodide crystal and its point defects,the emission and absorption mechanism are studied.The effects of all kinds of point defects on the emission spectrum of copper iodide crystal are also discussed.By the DVM method,(I₁₄Cu₁₆)²⁺ cluster is used in the simulations of pure copper iodide crystal.In addition,on the basis of(I₁₄Cu₁₆)²⁺ cluster,other clusters,such as copper vacancies,iodide vacancies,copper interstitial defects and iodide interstitial defects,have been studied as the main forms of its point defects.The excitation energy between different orbits is calculated by the transition state method,regarding the relaxation effect produced by the electronic transition in the crystal.Subsequently the computational result is compared with the experiments and the results by other simulation methods.The results of simulation of the pure copper iodide crystal show that the top of the valence band is consisted of I5p and Cu3d,and the bottom of the conduct band is consisted of Cu4s.The simulation result for the band gap of the pure crystal is 3.1eV,which is in good agreement with the experiment result.The calculation for point defects shows that the defects associated with the tetrahedron interstitial copper formed easier than that of other interstitial atoms in copper iodide crystal.The transition energies between Cu3d and Cu4s in copper tetrahedron interstitial defects are 3.2eV,which is presumed to be related to the broad luminescence bands of CuI crystal.The electronic structure of defects in CuI crystal is firstly calculated by DVM method.By the results,it can give some helpful clues for choosing certain dopants in copper iodide crystal to improve its scintillation charcteristic.And also it is very significative for the growth of super fast CuI sintillator.