  We study the pairwise concurrences, a measure of entanglement, of the ground
states for the frustrated Heisenberg ring to explore the relation between
entanglement and quantum phase transition associated with the momentum jump.
The groundstate concurrences between any two sites are obtained analytically
and numerically. It shows that the summation of all possible pairwise
concurrences is an appropriate candidate to depict the phase transition. We
also investigate the role that the momentum takes in the jump of concurrence at
the critical points. We find that an abrupt momentum change rusults in the
maximal concurrence difference of two degenerate ground states.
