Biomedical Engineering Reference
In-Depth Information
specifically choose the thirteen most closely packed combinations
of three atoms adsorbed on C atom “top” sites. Upon reconstruction,
hydrogen atom lateral positions generally do not deviate much from
the positions of the receiving C atoms shown in Fig. 5.5. A trimer is
so named because of its smallest H pairing component (o = ortho,
m = meta, and p = para) and distance of the trimer's third member
from the pair center. It means, for example, that the trimer labeled
1 is a three-hydrogen cluster, comprised of a pair of adjacently
adsorbed (ortho) hydrogen and a third H atom, adsorbed at the
closest distance from the aforementioned pair.
The pair energies have been computed using
E
= [
E
s
gr+2H(ads)
- (
are the
total energies for a graphene sheet, a gas phase H atom and a system
formed by an adsorbed H pair and graphene, respectively. Table 5.1
shows the trimers, arranged by adsorption energy, starting from the
most stable geometry.
E
+ 2
E
)]/2, where the terms
E
,
E
, and
E
gr
H(g)
gr
H(g)
gr+2H(ads)
Table 5.1
H trimer adsorption energies on graphene. Cells without
numeric values indicate that the specific pair (o = ortho, m =
meta, and p = para) is not part of the given trimer
E
s
E
o
E
m
E
p
to1
-1.39
-1.45
-2.60
—
to4
-1.39
-1.45
—
-1.43
tp1
-1.33
—
—
-1.23
to2
-1.24
-1.00
-2.15
-0.98
tm3
-1.22
—
-2.07
-0.90
to3
-1.19
-0.84
-1.99
—
to5
-1.18
-0.81
—
—
tm6
-1.17
—
-1.93
-0.76
to6
-1.14
-0.70
—
—
tm5
-0.80
—
-0.82
—
tm4
-0.79
—
-0.78
—
tm2
-0.78
—
-0.77
—
tm1
-0.74
—
-0.63
—
The values in the table have been computed by the following
expressions:
E
=
E
- (
E
+ 3
E
);
E
=
E
/3;
E
=
E
ads
gr+3H(ads)
gr
H(g)
s
ads
o
gr+3H(ads)
- (
E
+
E
);
E
=
E
+
- (
E
+
E
);
and
gr+2H(ortho)
H(g)
m
gr
3H(ads)
gr+2H(meta)
H(g)
