Electronic Band Structure and Fermi Surface of Heavy-Fermion Neptunium Superconductor NpPd5Al2

Abstract

Electronic band structure calculations were carried out for a new neptunium superconductor NpPd 5 Al 2 using a relativistic linear-augmented plane wave method within a local density approximation. The Fermi energy in the band structure is found to be located just on the 5 f -bands of the j =5/2 state with the extremely narrow band width and therefore the theoretical electronic specific heat coefficient γ b is extremely large, being γ b = 74.0 mJ/(K 2 ·mol), which is compared to γ= 390 mJ/(K 2 ·mol) estimated experimentally. NpPd 5 Al 2 is an uncompensated metal. The main electron Fermi surface corresponds to a doughnut-like flat Fermi surface centered at the Γ point which is connected with cylindrical Fermi surfaces elongated along the X–W–P line.