Relationship between Structure, Entropy, and Diffusivity in Water and Water-Like Liquids

Abstract

Anomalous behavior of the excess entropy (S(e)) and the associated scaling relationship with diffusivity are compared in liquids with very different underlying interactions but similar water-like anomalies: water (SPC/E and TIP3P models), tetrahedral ionic melts (SiO(2) and BeF(2)), and a fluid with core-softened, two-scale ramp (2SRP) interactions. We demonstrate the presence of an excess entropy anomaly in the two water models. Using length and energy scales appropriate for onset of anomalous behavior, we show the density range of the excess entropy anomaly to be much narrower in water than in ionic melts or the 2SRP fluid. While the reduced diffusivities (D*) conform to the excess-entropy-scaling relation, D* = A exp(alphaS(e)) for all the systems (Rosenfeld, Y. Phys. Rev. A 1977, 15, 2545), the exponential scaling parameter, alpha, shows a small isochore dependence in the case of water. Replacing S(e) by pair correlation-based approximants accentuates the isochore dependence of the diffusivity scaling. Isochores with similar diffusivity-scaling parameters are shown to have the temperature dependence of the corresponding entropic contribution. The relationship between diffusivity, excess entropy, and pair correlation approximants to the excess entropy are very similar in all the tetrahedral liquids.

Group Contribution Method for Viscosities Based on Entropy Scaling Using the Perturbed-Chain Polar Statistical Associating Fluid Theory

“…Goel et al 31 showed, that these scaling parameters can be correlated to the molecules chain length. Subsequent research on increasingly complex substances confirmed the monovariable relation for further n-alkanes [33][34][35] , for dumbbell-shaped particles 38 and water 32,36,39 . Limitations to the concept of transferable parameters were pointed out by Chopra et al 37 , which suggests that the entropy-scaling as a monovariable relation between dimensionless viscosity and residual entropy is a powerful, but component-specific concept.…”

“…For non-monoatomic fluids, the Rosenfeld-scaling does not obey a universal relation; for molecular substances the entropy scaling leads to component-specific, but still monovariable relations between the dimensionless viscosity and the residual entropy [31][32][33][34][35][36][37][38][39][40][41][42] . Using molecular simulations Goel et al 31 demonstrated a monovariable behaviour for Lennard-Jones chains.…”

Analytical model for three-dimensional Mercedes-Benz water molecules

“…11 The excess entropy is often used as a measure of the fluid’s structural order. Water’s excess entropy shows nonmonotonic trends along isotherms at low temperature, exhibiting a density range where compression anomalously increases excess entropy [58–62]. This trend is intimately related to water’s anomalous density trends in diffusivity [58–62], shear viscosity [58,61], and thermal conductivity [58].…”

Slow Dynamics and Structure of Supercooled Water in Confinement

“…This equation was tested by computer simulation in different liquid systems [62][63][64][65][66][67][68][69][70]. We considered in our work an equation similar to Equation (2) for the relaxation time τ in connection with the MCT.…”