  We study an extended Hubbard model with the nearest-neighbor Coulomb
interaction on the pyrochlore lattice at half filling. An interaction-driven
insulating phase with nontrivial Z_2 invariants emerges at the Hartree-Fock
mean-field level in the phase diagram. This topological insulator phase
competes with other ordered states and survives in a parameter region
surrounded by a semimetal, antiferromagnetic and charge ordered insulators. The
symmetries of these phases are group-theoretically analyzed. We also show that
the ferromagnetic interaction enhances the stability of the topological phase.
