First-principles modeling of oxygen interaction with SrTiO3(001) surface: Comparative density-functional LCAO and plane-wave study

TL;DR

This study uses first-principles DFT calculations with two different methods to analyze oxygen adsorption, migration, and electronic effects on SrTiO3(001) surfaces, relevant for various technological applications.

Contribution

It compares atomic orbital and plane wave DFT methods to provide detailed insights into oxygen interactions with SrTiO3 surfaces, highlighting the role of surface vacancies.

Findings

Atomic O binds strongly at bridge sites forming peroxide ions.

Molecular oxygen adsorption is weak (~0.25 eV) and dissociative adsorption is unfavorable.

Oxygen migration barrier is ~1 eV, higher than vacancy formation energy.

Abstract

Large scale first-principles calculations based on density functional theory (DFT) employing two different methods (atomic orbitals and plane wave basis sets) were used to study the energetics, geometry, the electronic charge redistribution and migration for adsorbed atomic and molecular oxygen on defect-free SrTiO3(001) surfaces (both SrO- and TiO2-terminated), which serves as a prototype for many ABO3-type perovskites. Both methods predict substantial binding energies for atomic O adsorption at the bridge position between the oxygen surface ions and an adjacent metal ion. A strong chemisorption is caused by formation of a surface molecular peroxide ion. In contrast, the neutral molecular adsorption energy is much smaller, ~0.25 eV. Dissociative molecular adsorption is energetically not favourable, even at 0 K. Adsorbed O atoms migrate along the (001) direction with an activation energy of ~1 eV which is much larger than that for surface oxygen vacancies (0.14 eV). Therefore, the surface O vacancies control encounter with the adsorbed O atoms and oxygen penetration to the surface which is the limiting step for many applications of ABO3-type perovskites, including resistive oxygen sensors, permeation ceramic membranes and fuel cell technology.