Carbon adsorption on V(100) was studied by both experimental methods and density functional theory. At low carbon coverages of thetaC = 0.18 ML and oxygen below the experimental detection limit, measured scanning tunneling microscopy (STM) images show both areas of local c(2x2) structure and <010> oriented rows of C atoms. At higher coverages of thetaC = 0.41 ML, mainly <010> oriented C rows with some local p(1x2) patterns are formed. The observed c(2x2) pattern is attributed to the presence of oxygen, since a mixture of carbon and oxygen favours the c(2x2) superstructure according to both the STM and the ab initio results. The calculations show that for thetaC = 0.50 ML the p(1x2) structure is more stable than c(2x2) by 0.13 eV per adsorbed atom. From the ab initio results it is predicted that p(1x2) changes into c(2x2) at a mixed coverage of about thetaC ~ 0.37 ML and thetaO ~ 0.13 ML. The geometry of the c(2x2) structure was determined using quantitative LEED showing good agreement with the ab initio data. Also the simulated STM images agree well with the experimental STM data.
Corresponding author: W. Bergermayer. Reprints also available from P. Varga (varga).
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