  The analytical forms of the interaction potentials between one S-wave and one
P-wave heavy mesons as well as the potentials between two P-wave heavy mesons
are deduced based on a chiral quark model. Our results explicitly show the
attractive property between two heavy mesons. Consequently, a series of
possible molecular states are obtained. It is expected that our study might
shed some light on the popular discussions of the newly observed XYZ states.
