Magnetism and superconductivity in C15 compounds from self-consistent band calculations

All-atom all-electron self-consistent semirelativistic linear muffin-tin orbital energy-band studies are reported for TiBe2, ZrZn2 (at ambient and high pressures), the high-Tc superconductor ZrV2, and the ultralow-Tc superconductor YAl2. Total and partial (by atom type and l values) density of states, Stoner-like parameters, electron-phonon coupling parameter and superconducting transition temperatures Tc (determined within the rigid muffin-tin approximation and McMillan's strong coupling theory with and without paramagnon contributions), and their behavior under applied pressure are used to discuss the origin of their observed magnetism and/or superconductivity. From an analysis of the results, we suggest possible high-Tc superconductivity at high pressure for ZrZn2, and its unlikely occurrence for TiBe2 unless dominant soft phonon modes exist.