  Previous studies of the structure of liquid water under pressure performed by
neutron diffraction, allowed us to establish two structural limits in liquid
water. These two limits are closely connected to the two known forms of
amorphous ice : the low density amorphous ice (LDA) and the high density
amorphous ice (HDA). In the present paper, we propose some interpretation of
our data in terms of a two level type model of water. This leads to show some
evidence of a liquid-liquid phase transition in liquid supercooled water. The
result looks in agreement with recent computer simulations that incorporate the
two forms of amorphous ice.
