  We consider a model of an optical cavity with a nonequilibrium reservoir
consisting of a beam of identical two-level atom pairs (TLAPs) in the general
X-state. We find that coherence of multiparticle nonequilibrium reservoir plays
a central role on the potential work capability of cavity. We show that no
matter whether there are quantum correlations in each TLAP (including quantum
entanglement and quantum discord) or not the coherence of the TLAPs has an
effect on the work capability of the cavity. Additionally, constructive and
destructive interferences could be induced to influence the work capability of
cavity only by adjusting the relative phase with which quantum correlations
have nothing to do. In this paper, the coherence of reservoir rather than the
quantum correlations effectively reflecting the effects of reservoir on the
system's work capability is demonstrated clearly.
