Liquid–liquid phase transitions: analytical approaches

Abstract

We consider liquid-liquid phase transitions as an indication of the local structure of condensed substances and investigate their statistics and thermodynamics. In this area there are two analytical approaches which describe the transitions: the first is purely phenomenological, while the second deals with intermolecular couplings. In the present work, we discuss the features of the above approaches and their applicability to metallic liquids.

Terahertz Signatures of Hydrate Formation in Alkali Halide Solutions

“…However, for K + , Rb + , Cs + , Cl – , Br – , and I – ions, the first ion–water binding energies are 17.9, 15.9, 13.7, 13.1, 12.6, and 10.6 kcal/mol, respectively. These binding energies are smaller than the binding energy of ice . As a result, these ions are extruded out of the hydrogen bond networks and tend to form many micro nonhydrated salt crystals.…”

“…The first binding energies of Li + , Na + , and F – ions to water molecules are 34, 24, and 23.3 kcal/mol, respectively . The binding energies of these ions are stronger than the total binding energy of 22.2 kcal/mol for the four saturated hydrogen bonds of each H 2 O in Ih ice . Thus, even at the eutectic temperature where these ions are recombined with other oppositely charged ions, the strongly bonded water molecules remain and are complementarily filled into their lattice vacancies to make the system the most stable (to minimize the Gibbs free energy of the system) and thereby form a salt hydrate.…”

“…46 The binding energies of these ions are stronger than the total binding energy of 22.2 kcal/mol for the four saturated hydrogen bonds of each H 2 O in Ih ice. 47 Thus, even at the eutectic temperature where these ions are recombined with other oppositely charged ions, the strongly bonded water molecules remain and are complementarily filled into their lattice vacancies to make the system the most stable (to minimize the Gibbs free energy of the system) and thereby form a salt hydrate. For example, for the NaCl solution, the binding energy of Na + is high enough to interact with the hydrating water molecules to develop many micro NaCl•2H 2 O crystals.…”

“…These binding energies are smaller than the binding energy of ice. 47 As a result, these ions are extruded out of the hydrogen bond networks and tend to form many micro nonhydrated salt crystals.…”

A polymerization scenario of the liquid–liquid transition of GeI4

“…These liquid states are thus said to be thermodynamically stable low-density liquid (Liq-II) and high-density liquid (Liq-I) phases. An LLCP scenario as represented by the pseudo-binary regular-solution model [10], a coarse-grained Potts model [11], and the Franzese-Stanley model [12] could capture equally well the location of these amorphous states and liquid phases on the pressure-temperature phase diagram [13]. Assuming that the breakpoint (located at 1.5 GPa and 950 K) of the melting curve of the crystalline phase (CP-I) is the triple point among the two liquid and crystalline phases, all these models consistently predicted that the LLCP that terminates the negatively sloped Liq-II-Liq-I phase boundary is closely located to the breakpoint [13].…”