Electronic Properties of Transuranium Compounds with HoCoGa${}_5$-Type Tetragonal Crystal Structure

Abstract

By using a relativistic linear augmented-plane-wave method with the one-electron potential in the local-density approximation, we investigate energy band structures and the Fermi surfaces of transuranium compounds NpTGa${}_5$, PuTGa${}_5$, and AmCoGa${}_5$ with transition metal atoms T. It is found in common that the energy bands in the vicinity of the Fermi level are mainly due to the large hybridization between $5f$ and Ga $4p$ electrons. For PuTGa${}_5$, we observe several cylindrical sheets of Fermi surfaces with large volume for T=Co, Rh, and Ir. The de Haas-van Alphen (dHvA) frequencies are theoretically estimated for PuCoGa${}_5$. It is also found that the Fermi surfaces of NpFeGa${}_5$, NpCoGa${}_5$, and NpNiGa${}_5$ are similar to those of UCoGa${}_5$, UNiGa${}_5$, and PuCoGa${}_5$, respectively, except for small details. For AmCoGa${}_5$, the Fermi surfaces are found to consist of large cylindrical electron sheets and small closed hole sheets, similar to PuCoGa${}_5$. The similarity is basically understood by the change of electron numbers inside the Fermi surfaces on the basis of a rigid-band picture. We discuss our theoretical Fermi surfaces with the dHvA experimental results on NpTGa${}_5$.

13 pages, 20 figures