On a molecular origin of properties of water

Using the Reference-Average-Mayer perturbation theory, effective temperature-dependent site-site potentials are constructed from a realistic water model to provide a missing direct link between complex force fields (intermolecular interaction models) and artificial simple theoretical models used to explain properties of supercooled water. It is shown, using the TIP4P interaction model, that the effective site-site interactions change qualitatively their character with changes of thermodynamic conditions and assume, at low temperatures, the form of a double well which gives rise to the existence of two meta-stable forms of supercooled water. Since the theory possesses capacity to provide the site-site correlation functions even in an analytic form it may form a basis for developing a molecular-based equation of state of water. (C) 2022 Elsevier B.V. All rights reserved.