Electronic energy band structure calculations for uranium compounds by a relativistic APW method

利用f电子的流动模型计算了典型铀化合物的电子能带结构。基于密度泛函理论在局域密度近似下构造了单电子势，并采用考虑自旋轨道相互作用的相对论增广平面波方法计算了能带。为了比较，用同样的方法对典型的铈化合物进行了能带计算。对于铀与元素周期表中第四族元素USi_3和UGe_3形成的aucu_3型化合物，费米能级的理论态密度与低温电子比热常数的实验值在定量上符合较好，费米表面可以较好地解释观测到的de Haas-van Alphen效应。理论与实验结果的一致性与三维过渡金属的结果一致。然而，能带理论不能很好地解释USn_3和UPb_3的实验结果。在CeSn_3中，4f电子与Sn的p态杂化强烈，被认为是一个典型的价涨落体系。然而，由于费米能级位于p波段，所以费米能级上的态密度不能变得很大。因此，由4f电子引起的异常在CeSn_3中并不明显。相比之下，CePd_3中的费米能级位于f带的底部附近，并且在4f带中存在小的电子和空穴费米面，其块态以几乎纯4f特征为主。简单分析表明，这些小费米面可能在CePd_3的电阻率异常行为中起重要作用。

Electronic energy band structures for typical uranium compounds were calculated using an itinerant model for f-electrons. One-electron potential was constructed based on the density-functional theory in a local-density approximation, and the energy bands were calculated by a relativistic augmented plane-wave method that takes into account the spin-orbit interaction. For the sake of comparison, band calculations were carried out also for typical cerium compounds by the same method.For the AuCu_3-type compounds which uranium forms with the elements of the group IV in the periodic table, such as USi_3 and UGe_3, the theoretical density of states at the Fermi lefel agrees quantitatively well with the experimental value derived from the low-temperature electronic specific heat constant, and the Fermi surface can explain reasonably well the observed de Haas-van Alphen effects. The agreement between theory and experiment is as good as those obtained for the 3d transition metals. However, band theory could not explain well experimental results for USn_3 and UPb_3.In CeSn_3, which is considered as a typical valence-fluctuation system, 4f electrons hybridise strongly with p states of Sn. Since the Fermi level, however, lies in the p bands, the density of states at the Fermi level cannot become very large. Therefore, anormalies due to 4f electrons in CeSn_3 are not sharp. In contrast, the Fermi level in CePd_3 is located near the botton in the f bands, and there exist small electron and hole Fermi surfaces in the 4f bands the block states on which consist dominantly with almost pure 4f character. Simple analysis suggests that these small Fermi surfaces may play an essential role in anomalous behaviours of the electrical resistivity of CePd_3.