%0 Journal Article %1 Ertl1977 %A Ertl, G. %A Neumann, M. %A Streit, K. M. %D 1977 %J Surf. Sci. %K science surface %P 393-410 %R 10.1016/0039-6028(77)90052-8 %T Chemisorption of CO on the Pt(111) surface %V 64 %X The system CO/Pt(111) was studied by means of LEED, thermal desorption and work function measurements. At 170 K a sqrt (3 )� sqrt(3)/R30� structure at theta = 1/3 is continuously transformed with increasing coverage into a c4 � 2 structure at theta = 1/2 and finally into a hexagonal close-packed layer with saturation at about theta = 0.68. Due to a decrease of the adsorption energy by about 4 kcal/mole at theta = 0.5 (=7.5 � 1014 molecules/cm^2) adsorption is completed at this coverage at room temperature. The initial adsorption energy is about 33 kcal/rnole. A strong tendency for disordering far below room temperature manifests itself with the LEED patterns and with the "Delta phi" data. The work function at first decreases, exhibits a (temperature-dependent) minimum at theta = 1/3, attains nearly the value of the clean surface at theta = 1/2 and again exhibits a second (shallow) minimum around theta = 0.6. A detailed discussion reveals that the observed effects may be explained by assuming the occupation of two different adsorption sites at theta less-than-or-equals, slant 0.5 with different dipole moments (presumably bridge (A) and threefold coordinated (B)) whose adsorption energy differs by only 0.5 kcal/mole. At low temperatures at theta = 1/2 sites A and at theta = 1/3 sites B are preferentially occupied whereas their small energy difference favours disordering at increasing temperature.

@article{Ertl1977, abstract = {The system CO/Pt(111) was studied by means of LEED, thermal desorption and work function measurements. At 170 K a sqrt (3 )� sqrt(3)/R30� structure at theta = 1/3 is continuously transformed with increasing coverage into a c4 � 2 structure at theta = 1/2 and finally into a hexagonal close-packed layer with saturation at about theta = 0.68. Due to a decrease of the adsorption energy by about 4 kcal/mole at theta = 0.5 (=7.5 � 1014 molecules/cm^2) adsorption is completed at this coverage at room temperature. The initial adsorption energy is about 33 kcal/rnole. A strong tendency for disordering far below room temperature manifests itself with the LEED patterns and with the "Delta phi" data. The work function at first decreases, exhibits a (temperature-dependent) minimum at theta = 1/3, attains nearly the value of the clean surface at theta = 1/2 and again exhibits a second (shallow) minimum around theta = 0.6. A detailed discussion reveals that the observed effects may be explained by assuming the occupation of two different adsorption sites at theta less-than-or-equals, slant 0.5 with different dipole moments (presumably bridge (A) and threefold coordinated (B)) whose adsorption energy differs by only 0.5 kcal/mole. At low temperatures at theta = 1/2 sites A and at theta = 1/3 sites B are preferentially occupied whereas their small energy difference favours disordering at increasing temperature.}, added-at = {2009-10-30T10:04:05.000+0100}, author = {Ertl, G. and Neumann, M. and Streit, K. M.}, biburl = {https://www.bibsonomy.org/bibtex/2eea57c3440f91aa638d7d9f47f08f596/jfischer}, doi = {10.1016/0039-6028(77)90052-8}, interhash = {93df0a536e687306dff82b6be26a3994}, intrahash = {eea57c3440f91aa638d7d9f47f08f596}, journal = {Surf. Sci.}, keywords = {science surface}, pages = {393-410}, timestamp = {2009-10-30T10:04:11.000+0100}, title = {Chemisorption of CO on the Pt(111) surface}, volume = 64, year = 1977 }