  We investigate how the quantum correlations (quantum discord) of a two-qubit
one dimensional XYZ Heisenberg chain in thermal equilibrium depends on the
temperature (T) of the bath and also on an external magnetic field B. We show
that the behavior of the thermal quantum discord (QD) differs in many
unexpected ways from the thermal entanglement. For example, we show situations
where QD increases with T when entanglement decreases, cases where QD increases
with T even in regions with zero entanglement, and that QD signals a quantum
phase transition even at finite T. We also show that by properly tuning B or
the interaction between the qubits we get non-zero QD for any T and we present
a new effect not seen for entanglement, the regrowth of thermal QD.
