Topological and real charge of Bjerrum defects in ices Ih and Ic

Abstract

Two mechanisms for the interaction of Bjerrum defects in ices are considered. (i) In the lattice ice models, the defects are topological charges interacting by the entropy of proton disorder. The charge magnitude is calculated by fitting the potential of mean force of a pair of defects (minus log of the simulated 3D distribution function) in the periodic boundary conditions to the Ewald summation energy. (ii) At the atomic level, the effective Coulomb charges for several classical water models are calculated as a sum of Gaussian-smoothed partial charges. The topological charge is equivalent to $\sim 20$% of the Bjerrum defect real charge.

GRAPHICAL ABSTRACT

Keywords:

• Bjerrum defect
• topological charge
• configurational entropy
• Gauss law

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by the Czech Science Foundation, project 18-16577S.