920860.fig.0013a
(a)
920860.fig.0013b
(b)
Figure 13: Phonon dispersion curves (a) in the instability (0.28,0.86) direction and (b) in the (1,1) direction, for  eV, ,  eV,  eV, and  eV. The solid curves correspond to the critical doping , the dot-dashed and the dotted curves correspond to and , respectively.