Thermal Contraction and Disordering of the Al(110) Surface
Nicola Marzari (1), David Vanderbilt (1), Alessandro De Vita (2), and, M.C. Payne (3) ((1) Department of Physics, Astronomy, Rutgers University,, (2) INFM, Department of Material Engineering, Applied Chemistry,, University of Trieste, (3) Cavendish Laboratory (TCM)
TL;DR
This study investigates the thermal behavior of the Al(110) surface up to 900 K, revealing anomalous contraction due to anharmonicity and free-electron-gas bonding, which may lead to surface disordering and premelting.
Contribution
It provides the first detailed molecular dynamics analysis of Al(110) surface contraction and disordering mechanisms at high temperatures.
Findings
Al(110) exhibits negative thermal expansion due to anharmonicity.
Shallow oscillation channels facilitate adatom-vacancy formation.
Surface disordering is linked to free-electron-gas bonding effects.
Abstract
Al(110) has been studied for temperatures up to 900 K via ensemble density-functional molecular dynamics. The strong anharmonicity displayed by this surface results in a negative coefficient of thermal expansion, where the first interlayer distance decreases with increasing temperature. Very shallow channels of oscillation for the second-layer atoms in the direction perpendicular to the surface support this anomalous contraction, and provide a novel mechanism for the formation of adatom-vacancy pairs, preliminary to the disordering and premelting transition. Such characteristic behavior originates in the free-electron-gas bonding at a loosely packed surface.
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