Stability and formation of hydroxylated <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>α</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi>Al</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mn>0001</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math> surfaces at high temperatures
Jiachen Chen, Dmitry Sharapa, Philipp N. Pleßow
Abstract
We report a type of termination of the $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}(0001)$ surface with low concentration of hydroxyl groups. Using density functional theory calculations, we show that this termination is more stable than previously reported structures for low chemical potentials of water. This means that hydroxyl groups remain thermodynamically stable up to much higher temperatures than predicted previously, for example, up to around 1000 K at 1 mbar partial pressure of water. We also study the formation of these hydroxylated surfaces from adsorbed water and show that the initial steps for surface reconstruction are favorable thermodynamically and also proceed with accessible barriers.