Properties of pure water and sodium chloride solutions at high temperatures and pressures: a simulation study

Abstract

The structural and thermodynamic properties of pure water and sodium chloride solutions at high temperatures and pressures are studied by using molecular dynamics simulations and quantum molecular simulations. Properties are calculated as functions of temperature and pressure. The results show that the structure of pure water becomes looser as temperature increases from 298 to 400 K, with the collapse of the traditional tetrahedral structure. For sodium chloride solutions, the same collapse is also found with the increased concentration. Moreover, a critical point for the diffusion coefficient of and is evident when the temperature increases linearly under 100 atm. At the critical points, the ions are abnormally clustered, due to the weakly hydrogen-bonded water molecules. The cluster size of the ions is synchronous with the corresponding diffusion coefficients.

Keywords::

• NaCl
• water solution
• molecular dynamics simulation
• quantum chemical simulation
• high temperature and pressure

Acknowledgements

This work was supported by the National Natural Science Foundation of China [grant number 11025524], [grant number 11161130520], National Basic Research Program of China [grant number 2010CB832903] and the European Commissions 7th Framework Programme (FP7-PEOPLE-2010-IRSES) [grant agreement project number 269131].

Disclosure statement

No potential conflict of interest was reported by the authors.