  Molecular Dynamic and Monte Carlo studies are performed in a family of
core-softened (CS) potential, composed by two length scales: a repulsive
shoulder at short distances and the another a variable scale, that can be
repulsive or strongly attractive depending on the parameters used. The density,
diffusion and structural anomalous regions in the pressure versus temperature
phase diagram shrink in pressure as the system becomes more attractive. The
liquid-liquid transition appears as a consequence of the non monotonic behavior
of the density versus pressure isotherms with the increase of the attraction
well. We found that the liquid-gas phase transition is Ising-like for all the
CS potentials and its critical temperature increases with the increase of the
attraction. No Ising-like behavior for the liquid-liquid phase transition was
detected in the Monte Carlo simulations what might be due to the presence of
stable solid phases.
