Surface of aqueous solutions of alkali halides: layer by layer analysis

ABSTRACT

Interfacial layers of both vapour/liquid and crystal/liquid aqueous solutions of sodium and caesium halides have been analysed in detail using four different methods for the identification of interfacial molecules and layers, and both non-polarisable and polarisable models. It is found that each of the methods yields a somewhat different result with the best mutual agreement found between the ITIM (Identification of Truly Interfacial Molecules) and α-shape-based USTI (Universal Scheme for Triangulated Interfaces) methods. Concerning the water models, the commonly used JC [I. S. Joung, T. E. Cheatham, J. Phys. Chem. 112 (2008) 9020] model predicts the structural properties of the vapor/liquid interface different from both the non-polarisable MADRID and polarisable AH/BK3 models, and also from experiment. The same applies also to the structural properties of the solid–liquid interface; although the AH/BK3 and JC models yield a surplus of chlorine ions, a segregation of Na${}^{+}$ and Cl⁻ ions in the interfacial layers predicted by the JC model is not observed in the polarisable model.

KEYWORDS:

• Solutions of electrolytes
• sodium halides
• caesium halides
• interfacial layers analysis
• vapor–liquid interface
• solid–liquid interface

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Ivo Nezbeda http://orcid.org/0000-0003-1882-0587

Additional information

Funding

Support for this work was provided by the Czech Science Foundation [grant no. 16-02647S]. Access to computing and storage facilities owned by parties and projects contributing to the National Grid Infrastructure MetaCentrum provided under the programme ‘Projects of Large Research, Development, and Innovations Infrastructures’ (CESNET LM2015042) is greatly appreciated.