Antiphase domain boundaries at the Fe₃O₄(001) surface

Abstract

Antiphase domain boundaries (APDBs) in the (√2 × √2)R45° reconstruction of the Fe₃O₄(001) surface were investigated using scanning tunneling microscopy (STM) and density functional theory [(DFT) + U] calculations. The equilibrium structure of the APDBs is interpreted in terms of the distorted B-layer model for the (√2 × √2)R45° reconstruction in which a lattice distortion couples to charge order in the subsurface layers. The APDBs are observed after prolonged annealing at 700 °C, indicating that they are extremely stable. DFT + U calculations reveal that the APDB structure is linked to a disruption in the subsurface charge-order pattern, leading to an enrichment of Fe²⁺ cations at the APDB. Simulated STM images reproduce the appearance of the APDBs in the experimental data and reveal that they are preferential adsorption sites for hydrogen atoms.