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Title: Density functional theory investigations of surface structure and surface stress in adsorbate layers on Cu, Pd and Ir surfaces
Author: Bradley, Matthew K.
ISNI:       0000 0004 2726 4858
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2012
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An introduction to surface structure and plane wave density functional theory (DFT) is presented along with theoretical studies of seven adsorbate systems. A new energetically favourable structure of low symmetry is found for furan on Pd(111) that is entirely consistent with previous experimental findings from scanned-energy mode photoelectron diffraction (PhD). In addition, it is found that the C3H3 decomposition product of furan on the same surface is likely to be adsorbed in a propargyle conformation (CH-C-CH2) although some cooccupation of the molecule in a half benzene conformation (CH-CH-CH) is also possible. Methoxy is found to adsorb at local short bridge sites only on Cu(110), occupying locations both above the clean surface and above pairs of surface Cu adatoms. Simulated scanning tunneling microscope (STM) images of the (5×2) reconstruction are found to be in qualitative agreement with previous images recorded experimentally. The experimentally determined local structure of cytosine on the same surface is confirmed and models are proposed for the (6×6) reconstruction. An increased tensile surface stress is found to be associated with the Ir(001)(1×1) ! Ir(001)(5×1)-hex phase transition, thus confirming that the reconstruction is not a consequence of the large surface stress of bulk terminated Ir(001). In contrast, H adsorption on Ir(001) (5×1)-hex does lead to a reduction of the surface stress in the range 1.76-2.06 Nm−1 for a H coverage range 0.6-0.8 ML in excellent agreement with the experimentally-determined value of 1.7 Nm−1. The energetically favourable structure for methanethiolate adsorption on Cu(100) is found to be a c(6×2) missing row structure that allows effective relief of surface stress. On Cu(111) several complex overlayer models for methanethiolate adsorption have similar associated surface energy, suggesting that the local structure is dependent on the availability of Cu adatoms. For adsorption on both surfaces, agreement with previous STM images and MEIS results is discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics