# A two-dimensional hexagonal sheet of TiO$_2$

## TL;DR

This paper reports the discovery of a novel two-dimensional hexagonal TiO$_2$ sheet with unique properties, stable against stress, chemically inert, and with a tunable large bandgap, using ab initio methods and neural network potentials.

## Contribution

The study introduces a new stable 2D TiO$_2$ structure based on a honeycomb lattice, identified through advanced computational searches, with potential for various applications.

## Key findings

- Hexagonal TiO$_2$ sheet is energetically favorable compared to known structures.
- The sheet is mechanically stable and chemically inert.
- It exhibits a large, strain-tunable bandgap of 5.05 eV.

## Abstract

We report on the ab initio discovery of a novel putative ground state for quasi two-dimensional TiO$_2$ through a structural search using the minima hopping method with an artificial neural network potential. The structure is based on a honeycomb lattice and is energetically lower than the experimentally reported lepidocrocite sheet by 7~meV/atom, and merely 13~meV/atom higher in energy than the ground state rutile bulk structure. According to our calculations, the hexagonal sheet is stable against mechanical stress, it is chemically inert and can be deposited on various substrates without disrupting the structure. Its properties differ significantly from all known TiO$_2$ bulk phases with a large gap of 5.05~eV that can be tuned through strain engineering.