  We study the doping dependence of the spin-density-wave (SDW) state in four
models of the 1111 pnictides. The random-phase approximation is used to
determine the ordering temperature and the ordering vector as functions of
doping, and to evaluate the contribution of the various orbitals to the SDW
instability. In addition to the usual assumption of orbitally
rotation-invariant interactions, we consider the effect of reduced interactions
involving the xy orbital, which are anticipated by crystal-structure
considerations. We find that changing the relative strength of the interaction
in the xy orbital tunes the system between different nesting instabilities
leading to similar SDW order. We identify two models as showing reasonable
agreement with experiments, while the other two display significant
discrepancies, and discuss the underlying differences between the models.
