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Electronic structure and STM images of Na on Al(111)
Author(s) -
Máca F.
Publication year - 1999
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/(sici)1096-9918(199905/06)27:5/6<555::aid-sia507>3.0.co;2-i
Subject(s) - scanning tunneling microscope , low energy electron diffraction , chemistry , electronic structure , ab initio , crystallography , surface (topology) , molecular physics , surface reconstruction , ab initio quantum chemistry methods , electron diffraction , diffraction , geometry , condensed matter physics , computational chemistry , physics , molecule , optics , mathematics , organic chemistry
Recently, extensive ab initio calculations predicted a veryunusual ordered‐surface alloy structure for the adsorbatesystem Na on Al(111) at a coverage of Θ=0.5.For this surface structure a surprisingly strong intermixing of Naand Al atoms has been reported. Subsequently, this complicatedgeometry was confirmed in great detail by low‐energy electrondiffraction and surface‐extended x‐ray adsorption finestructure experiments. However, a scanning tunnelling microscopy(STM) study arrived at a significantly differentinterpretation for the surface geometry. Using the full‐potential linearized‐augmentedplane‐wave method we have evaluated the surface electronicstructure and valence densities for the theoretically predictedgeometry and we simulated STM images by employing theTersoff–Hamann approach. The calculated STM images exhibit onlyone corrugation per surface unit cell (for a bias up to −1eV), which is in accord with the experimental STM results. Thecharge transfer from alkali atoms to the substrate makes Na atoms inthis imaging regime nearly invisible in STM. Thus, theTersoff–Hamann interpretation scheme starting from correctsurface geometry is consistent with the STM data, and the difficultyin identifying structures in measured STM images with atoms issolved. The interpretation of the STM image is in agreement with theabove‐mentioned experiments and calculations. We also comparethese results to those of additional calculations forΘ=1/3, i.e. the (√3×√3)structure of Na on Al(111). Copyright © 1999 JohnWiley & Sons, Ltd.