Investigation on the electronic structure of the actinide dioxide by the relativistic band calculation incorporating the effect of CEF potential.

本课题的主要目的是研究强相关电子系的相关二氧化锕系，并发展基于晶体电场势效应的相对论能带计算。AnO_2（An=U, Np, Pu, Am）的电子结构可以用适当的能带结构计算技术在局部密度近似（LDA）中简单地理解，但实际上，在LDA中正确地再现半导体行为并不容易。由于在立方对称的二氧化锕系的萤石结构中，在LDA方法中Γ_7能级应该低于Γ_8能级，所以当我们在这种能级方案中简单地容纳4个f电子时，我们不能得到AnO_2的Γ_1单重态基态。为了改善这种情况，我们提出了一种新的思路，即在用LDA计算带结构时明确考虑晶体电场（CEF）电位的影响。将RLAPW方法与CEF方法相结合，开发了相对论能带计算程序。该方法应用于锕系二氧化物。因此，我们在强相关电子系统中研究二氧化锕系元素的策略被证明是有用的，并且已经得到了发展。

The main purposes of this project were to study related actinide dioxide of strongly correlated electron systems, and to development the relativistic band calculation based on the effect of crystalline electric field potential. The electronic structure of AnO_2(An=U, Np, Pu, Am) is simply understood with the use of an appropriate band-structure calculation technique in a local density approximation (LDA), but in actuality, it is not so easy to reproduce correctly semiconducting behavior in the LDA. Since in the fluorite structure of actinide dioxide with cubic symmetry, Γ_7 level should be lower than Γ_8 one in the LDA approach, we do not obtain the Γ_1 singlet ground state for AnO_2, when we simply accommodate four f electrons in such a level scheme. In order to improve the situation, we proposed a new idea to consider explicitly the effect of crystalline electric field (CEF) potential in the band-structure calculation with the LDA. The relativistic band calculation program was developed by the combination of the RLAPW and the CEF method.The method was applied to actinide dioxides. Thus our strategy to study the actinide dioxide in strongly correlated electron systems is shown to be useful and has been developed.