Single-file mobility of water-like fluid in a generalized Frenkel-Kontorova model

TL;DR

This study investigates how water molecule mobility inside carbon nanotubes varies with substrate potential and commensuration, revealing complex regimes and dependencies through simulations and analytical modeling.

Contribution

It introduces a generalized Frenkel-Kontorova model to analyze water mobility in nanotubes, uncovering non-monotonic behaviors and multiple mobility regimes.

Findings

Mobility decreases monotonically with increasing substrate potential amplitude.

Mobility exhibits non-monotonic behavior with respect to commensuration ratio.

Three distinct mobility regimes are identified based on the commensuration ratio.

Abstract

In this work we used a generalized Frenkel-Kontorova model to study the mobility of water molecules inside carbon nanotubes with small radius at low temperatures. Our simulations show that the mobility of the confined water decreases monotonically increasing the amplitude of the substrate potential at fixed commensurations. On the other hand, the mobility of the water molecules shows a non-monotonic behavior when varying the commensuration. This result indicates that the mobility of the confined fluid presents different behavior regimes depending on the amplitude of the water-nanotube interaction. In order to understand qualitatively these results, we study analytically the driven Frenkel-Kontorova model at finite temperatures. This analysis allows us to obtain the curves of the mobility versus commensurations, at fixed substrate potentials. Such curves shows the existence of three regimes of mobility behavior as a function of the commensuration ratio. Additionally, our study indicates a nontrivial and strong dependence of the mobility with a quantity that can be interpreted as an effective amplitude of the substrate potential, depending on the bare amplitude of the substrate potential, the commensuration ratio and temperature.