Structural and chemical mechanisms governing stability of inorganic Janus nanotubes

TL;DR

This study uses Density Functional Theory to understand how asymmetric Janus sheets self-assemble into inorganic nanotubes, revealing key mechanisms and identifying over 100 small-radius nanotubes with potential unique properties.

Contribution

It uncovers the lattice mismatch and chemical bond differences as mechanisms driving nanotube formation in Janus sheets, and introduces descriptors and Bayesian methods for predicting nanotube radii.

Findings

Over 100 nanotubes with radii below 35 Å identified

Lattice mismatch drives isovalent Janus nanotube formation

Chemical bond strength differences influence non-isovalent nanotube formation

Abstract

One-dimensional inorganic nanotubes hold promise for technological applications due to their distinct physical/chemical properties, but so far advancements have been hampered by difficulties in producing single-wall nanotubes with a well-defined radius. In this work we investigate, based on Density Functional Theory (DFT), the formation mechanism of 135 different inorganic nanotubes formed by the intrinsic self-rolling driving force found in asymmetric 2D Janus sheets. We show that for isovalent Janus sheets, the lattice mismatch between inner and outer atomic layers is the driving force behind the nanotube formation, while in the non-isovalent case it is governed by the difference in chemical bond strength of the inner and outer layer leading to steric effects. From our pool of candidate structures we have identified more than 100 tubes with a preferred radius below 35 {\AA}, which we hypothesize can display unique properties compared to their parent 2D monolayers. Simple descriptors have been identified to accelerate the discovery of small-radius tubes and a Bayesian regression approach has been implemented to assess the uncertainty in our predictions on the radius.