Chemical bond formation showing a transition from physisorption to chemisorption
Abstract
Surface molecules can transition from physisorption through weak van der Waals forces to a strongly bound chemisorption state by overcoming an energy barrier. We show that a carbon monoxide (CO) molecule adsorbed to the tip of an atomic force microscope enables a controlled observation of bond formation, including its potential transition from physisorption to chemisorption. During imaging of copper (Cu) and iron (Fe) adatoms on a Cu(111) surface, the CO was not chemically inert but transited through a physisorbed local energy minimum into a chemisorbed global minimum, and an energy barrier was seen for the Fe adatom. Density functional theory reveals that the transition occurs through a hybridization of the electronic states of the CO molecule mainly with s-, pz-, and dz2-type states of the Fe and Cu adatoms, leading to chemical bonding.
- Publication:
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Science
- Pub Date:
- October 2019
- DOI:
- 10.1126/science.aay3444
- Bibcode:
- 2019Sci...366..235H
- Keywords:
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- CHEMISTRY