Phase Diagram for Ionic Liquids

Abstract

Abstract Dimensionless reduced melting point T* (thermal energy at the melting point related to the energy of Coulombic interaction) and volume V* (molar volume related to the volume occupied by ions) were calculated from experimental data available in the literature. Calculations were performed for a number of 1:1 valent salts, having melting points in the range from 254 K (room temperature ionic liquid [EtMeIm+][NTf2 −]) and 1268 K (NaF). While the reduced melting temperature was approximately constant (0.12 ± 0.03), the reduced molar volume differed considerably (0.255–1.050). Pairs of V*;T* parameters were used for the construction of a V* = f(T*) phase diagram, which showed one vertical line, indicating regions of salt existence in the solid and liquid states. All V*, T* points, calculated for salts of different melting points, were at the same line.