Electronic properties of the novel 18-K superconducting Y_2C_3 as compared with 4-K YC_2 from first principles calculations

摘要

The electronic band structure and ground state properties of the recently discovered 18-K superconducting Y_2C_3 material (Akimitsu et al., 2004) have been examined by the full-potential linear muffin-tin method-generalized gradient approximation method and compared with those of the 4-K superconductor YC_2. The calculations show that the growth of T_C for the yttrium sesquicarbide as compared with 4-K YC_2 may be due to the electronic factor: the near-Fermi DOS for Y_2C_3 was found to be about 36.7% higher that for YC_2. The Fermi level of the 'ideal' Y_2C_3 is located near the local DOS minimum, and the superconductivity of Y_2C_3-based materials will be very sensitive to synthesis conditions (for example, pressure and annealing effects) and the presence of various impurities and lattice vacancies. Probably these factors may be used to vary the superconductivity of the Y_2C_3 phase over a wide range.