A model for the phase separation controlled by doping and the internal   chemical pressure in different cuprate superconductors
  In the framework of a two-band model, we study the phase separation regime of different kinds of strongly correlated charge carriers as a function of the energy splitting between the two sets of bands. The narrow (wide) band simulates the more localized (more delocalized) type of charge carriers. By assuming that the internal chemical pressure on the CuO$_2$ layer due to interlayer mismatch controls the energy splitting between the two sets of states, the theoretical predictions are able to reproduce the regime of phase separation at doping higher than 1/8 in the experimental pressure-doping-$T_c$ phase diagram of cuprates at large microstrain as it appears in overoxygenated La$_2$CuO$_4$. 
K.I. Kugel, A.L. Rakhmanov, A.O. Sboychakov, Nicola Poccia, and   Antonio Bianconi