Abstract
Density functional theory calculations have been used to investigate CO adsorption on three surface terminations of χ-Fe5C2 in the presence of carbon vacancy sites. CO did not show a strong energetic preference for a particular adsorption site on each surface, since similar adsorption energies were obtained for structurally distinct adsorption configurations. In addition, it was found that the adsorption of CO in a vacancy site is not necessarily more favorable energetically, compared with adsorption in alternative Fe sites. The presence of a subsurface carbon atom directly below a 4-fold site was found to inhibit or significantly destabilize adsorption of CO in that site. The role of step sites in activating CO has been investigated by comparing the calculated adsorption energies, structural properties, and vibrational stretching frequencies of CO adsorbed in equivalent sites in the presence or absence of steps. Coordination of CO to the surface through both ends of the molecule was associated with a len...
Published Version
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