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.
%0 Journal Article
%1 Ertl1977
%A Ertl, G.
%A Neumann, M.
%A Streit, K. M.
%D 1977
%J Surface Science
%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 = {2009-10-01T16:01:09.000+0200},
author = {Ertl, G. and Neumann, M. and Streit, K. M.},
biburl = {https://www.bibsonomy.org/bibtex/21d248edf940430a7dddacbabe74f8f37/jfischer},
doi = {10.1016/0039-6028(77)90052-8},
interhash = {93df0a536e687306dff82b6be26a3994},
intrahash = {1d248edf940430a7dddacbabe74f8f37},
journal = {Surface Science},
keywords = {science surface},
pages = {393-410},
timestamp = {2009-10-01T16:01:10.000+0200},
title = {Chemisorption of CO on the Pt(111) surface},
volume = 64,
year = 1977
}