Polar or not polar? The interplay between reconstruction, Sr enrichment, and reduction at the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">La</mml:mi><mml:mrow><mml:mn>0.75</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Sr</mml:mi><mml:mrow><mml:mn>0.25</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>MnO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> (001) surface
Franziska Heß, Bilge Yildiz
Abstract
Polar surfaces created upon truncation of a crystal are unstable and give rise to surface reconstruction and defect segregation. Employing a computational approach, we identify an unpolar reconstruction of the La${}_{0.75}$Sr${}_{0.25}$MnO${}_{3+\ensuremath{\delta}}$ perovskite (001) surface. Its main characteristics are the association of cation and oxygen vacancies, and presence of the dopant, Sr, at the surface. This surface structure can be a key puzzle piece to understand the interaction of perovskite oxide surfaces with small molecules in the gas phase, such as O${}_{2}$, H${}_{2}$O, and CO${}_{2}$. And finding this surface structure and the conditions that stabilize it is an important step for rationally designing materials with long term stability in energy conversion and catalysis.