A repulsive interaction model of superconductivity (SC) is studied for tight-binding models with three-fold degenerate molecular orbitals. Taking a weak-coupling approach, we derive dimensionless coupling constants for various symmetries of SC pairs. In addition to anisotropic SC pairs, the s-wave (A g) pairing can also be formed. With the purely repulsive interaction, however, the Ag pair is not the most stable in both bcc and fcc lattices. The most stable SC pair for the bcc lattice has the Tg symmetry, which is favored by a strongly nesting Fermi surface. In the fcc lattice, various SC symmetries have comparable coupling strengths. With the electron-phonon interaction combined, it is likely that the Ag pair becomes the most stable.
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