Molecular simulations of the thermal conductivity of liquid water using the TIP4P/Ice and TIP4P/2005 models

Relying on the Green-Kubo linear response theory, equilibrium molecular dynamics simulations are performed to estimate the thermal conductivity of liquid water. First, using two rigid TIP4P-like water models, the density of liquid water is determined under various temperature (250-350 K) and pressure (1-100 bar) conditions. With an appropriate density, the thermal conductivity of liquid water is then estimated from the heat flux auto-correlation function. In line with previous simulation studies, the thermal conductivities determined using the two water models are found to be very close but higher than the experimental data. Moreover, the power spectrum analysis and regression procedure are performed to extract the acoustic and optical-like/intramolecular modes shown in the heat flux auto-correlation function. Despite many limitations, the analytical expression for energy transfer times between neighboring water molecules explains well the rapid convergence of thermal conductivity as a result of the reduced optical-like contribution being compensated by the acoustic component. In addition, the impacts of temperature and pressure on the thermal conductivity of liquid water are also assessed.