Revisiting the (110) Surface Structure of TiO2: A Detailed Theoretical Analysis

TL;DR

This paper provides a detailed theoretical reanalysis of the TiO2 (110) surface structure, resolving previous discrepancies with experimental data through improved computational methods and insights into slab modeling.

Contribution

It offers a refined theoretical approach that aligns closely with high-precision experimental results and discusses best practices for modeling and reporting surface structures of covalent solids.

Findings

Achieved excellent agreement with experimental LEED-IV data.

Bond lengths converge faster with slab thickness than atomic positions.

Freezing bottom layers in models can be effective for surface simulations.

Abstract

A detailed reexamination of the (110) surface structure of rutile TiO2 has been carried out using first-principles total-energy methods. This investigation is in response to a recent high-precision LEED-IV measurement revealing certain significant quantitative discrepancies between experiment and previous theoretical calculations. We have been able to resolve these discrepancies and achieve excellent quantitative agreement with experiment by judicious attention to reducing computational approximation errors. Our analysis also reveals that bond lengths converge much faster with slab thickness than do relaxed absolute atomic positions, which are the structural parameters typically reported in the literature for this and related systems. The effect this observation has on both the choice of slab models and the way in which surfaces structures should be reported for covalently bonded solids is discussed. Finally, the efficacy of freezing the lowest several atomic layers of TiO2 slab models in their bulk-like positions is examined.