  Orbital-ordering instability arising due to the intrapocket nesting is
investigated for the tight-binding models of pnictides in the presence of
orbital-lattice coupling. The incommensurate instabilities with small momentum,
which may play an important role in the nematic-ordering transition, vary from
model to model besides being more favorable in comparison to the spin-density
wave instability in the absence of good interpocket nesting. We also examine
the doping dependence of such instabilities. The electron-phonon coupling
parameter required to induce them are compared with the first-principle
calculations.
