Thermodynamic response functions and Stokes-Einstein breakdown in superheated water under gigapascal pressure

Liquid water is the most intriguing liquid in nature, both because of its importance to every known form life, and numerous anomalous properties, largely magnified under supercooled conditions. Among properties seeming divergence thermodynamic response functions dynamic below homogenous nucleation temperature (~ 232 K). Furthermore, exhibits an increasingly decoupling viscosity diffusion, upon cooling, resulting breakdown Stokes-Einstein relationship (SER). At high temperatures pressures, however, behaves more like a “simple” liquid. Nonetheless, experiments at 400 K GPa pressures (Bove et al. (2011) Phys. Rev. Lett., 111:185,901) showed that although diffusion decreases monotonically with pressure, opposite pressurized water, larger than found normal observed. Here, we studied validity SER different pressure-dependent functions, exhibit abnormal behavior including density, isothermal compressibility, thermal expansion coefficient along isotherm up 3 through molecular dynamics simulations. Seven models were investigated. A monotonic increase density 50%) decrease compressibility 90%) 65%) found. Our results also show compressed hot has various resemblances cool pressure inducing formation new second coordination sphere coefficients. Whereas all provide good account viscosity, magnitude violation (> ~ 1 GPa) significantly smaller experiments. Thus, simulations comparable observed for indicating possible limitations local structure self-diffusion superheated above GPa.