高能量,大注量中子辐照下α-Al_2O_3中的F_3聚集型色心电子结构及其吸收光谱研究

THE ELECTRONIC STRUCTURE AND ABSORPTION SPECTRUM OF HIGH-ENERGY AND GREAT FLUX NEUTRON RADIATION INDUCED F 3 CENTER IN α-Al 2O 3

利用嵌入原子簇模型结合Ｆ心的类Ｈ离子波函数研究了α－Ａｌ２Ｏ３晶体中Ｆ３聚集型色心存在时，晶体的能带结构，态密度，Ｍｕｌｉｋｅｎ电荷布居的变化，讨论了色心的光学吸收跃迁模式。结果表明，由于Ｆ３聚集心的存在，在α－Ａｌ２Ｏ３中引入了１个单能级和１个２重简并色心能级，产生了一个３．５４ｅＶ的从色心能级到导带底的新的吸收跃迁。经与高能量，大注量中子辐照后的刚玉晶体的光学吸收实验结果比较，我们认为实验测得的０．３５６μｍ（３．４８３ｅＶ）处的吸收峰是由于Ｆ３聚集心的电子的吸收跃迁所引起的。同时，也发现Ｆ３聚集心的格点处的电荷布居比单Ｆ心格点处的电荷布居小。

This paper study the various of energy band structure,density of state, Mulliken charge density when the F 3-center is in the alumina by using the embedded-cluster of Al 2O 3 and H-like wave function of F-center,also discuss the optical transition models of color center.We find existing one single energy level and one doubly-degenerate energy level in the fundamental gap when the F 3-center in the crystal,and there is a new 3.54 eV transition from defect energy level to condition band.Comparing with the absorption spectrum of alumina by high-energy and great flux neutron radiation,we think that the 0.356 μm(3.483 eV)absorption peak is due to the F 3-center. Also,we find the charge density is more little in the site of F 3-center Than F-center in alumina crystal.