| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1987: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1986: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1985: ¥600,000 (Direct Cost: ¥600,000)
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| Research Abstract |
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.
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