A liquid–liquid critical point (or LLCP) is the endpoint of a liquid–liquid phase transition line (LLPT); it is a critical point where two types of local structures coexist at the exact ratio of unity.
This hypothesis was first developed by Peter Poole, Francesco Sciortino, Uli Essmann and H. Eugene Stanley in Boston[1] to obtain a quantitative understanding of the huge number of anomalies present in water.
The ratio between HD and LD configurations is determined according to the thermodynamic equilibrium of the system, which is often governed by external variables such as pressure and temperature.
[3] The liquid–liquid critical point theory can be applied to several liquids that possess the tetrahedral symmetry.
The study of liquid–liquid critical points is an active research area with hundreds of articles having been published, though only a few of these investigations have been experimental[4][5][6][7][8][9] since most modern probing techniques are not fast and/or sensitive enough to study them.