Chemistry Reference
In-Depth Information
TABLE 11.3
Isomers of Lithium Clusters
Li
n
This Work (Big Bang)
Jones
[40]
Gardet
[41]
3
C
2v
P
,.D
∞h
L
C
2v
P
,.D
∞h
L
C
2v
P
4
D
2h
P
D
2h
P
D
2h
P
5
C
2v
,.C
2v
P
C
2v
,.C
2v
P
C
2v
,.C
2v
P
6
D
4h
,.C
5v
,.D
3h
,.(D
2d
)
D
4h
,.C
5v
,.D
3h
D
4h
,.C
2v
,.D
3h
7
D
5h
,.C
3v
,.(C
s
)
D
5h
,.C
3v
D
5h
8
T
d
,.(C
3v
),.(C
s
)
D
5h
,.T
d
,.C
2v
T
d
,.C
2v
,.C
s
9
C
4v
,.C
2v
,.C
s
C
s
,.C
4v
C
2v
,.C
s
10
(D
2d
),.(C
s
),.(C
4v
),.(T
d
)
C
1
,.C
2V
C
1
,.C
2V
11
C
2
,.(C
2v
),.(C
2
),.(C
s
)
C
2
12
C
s
,.(C
s
),.(C
2v
)
C
s
13
(C
s
),.(C
s
),.(C
2
),.(C
1
),.(C
1
),.(C
3v
)
C
s
,.C
1
14
(C
2
),.(C
s
),.(C
3v
),.(C
s
),.(C
1
),.(C
1
)
15
(C
4v
),.(C
1
),.(C
2
),.(C
s
),.(C
1
),.(C
s
),.(C
s
)
16
(C
s
),.(C
1
),.(C
1
),.(C
1
),.(C
1
)
17
(C
1
),.(C
s
),.(C
1
)
18
(C
s
),.(C
1
),.C
5v
,.(C
1
),.(C
1
),.(C
1
),.(C
s
),.(C
1
),.(C
4v
)
C
5v
,.D
5h
,.D
3h
,.C
1
19
(C
2v
),.(C
s
),.(C
1
),.(C
1
)
D
5h
20
C
s
,.(C
1
),.C
2v
,.(C
1
),.(C
1
),.(C
1
)
C
2v
,.C
s
11.4 ANALYSIS OF THE CHEMICAL BONDING AND
REACTIVITY OF ATOMIC CLUSTERS
Most.atomic.clusters.possess.very.labile.bonds.that.do.not.follow.the.ordinary.chem-
ical.rules.describing.the.bonding.and.geometry.of.ordinary.molecules.such.as.hydro-
carbons..For.instance,.they.can.present.a.lower.or.higher.coordination.than.the.one.
dictated. by. the. number. of. valence. electrons:. the. simple. octet. rule. is. almost. never.
followed..Therefore,.the.number.of.possible.isomers.increases.dramatically.(usually.
exponentially). with. the. number. of. atoms,. and. chemical. intuition. does. not. help. in.
predicting.the.most.stable.isomer..This.presents.two.issues.to.the.theoretical.calcula-
tions..First,.how.can.one.ind.the.most.stable.isomers.(global.minima).when.most.
optimization. techniques. do. not. guarantee. that. a. global. minimum. will. be. found?.
Second,.how.can.one.understand.the.bonding.between.the.atoms.in.a.cluster?.Once.
the.geometric.parameters.of.the.lowest.energy.isomers.of.a.given.cluster.are.known,.
the.task.is.to.try.and.understand.the.way.the.atoms.are.bonded.to.one.another..This.
knowledge.permits.the.prediction.of.new.geometries.and.the.prediction.of.the.class.
of. reactivity. the. cluster. can. undergo.. Unfortunately,. this. is. not. an. easy. task,. and.
until.recently.there.has.been.no.simple.model.for.understanding.bonding.in.atomic.
clusters..Generally,.the.Lewis.electron.pair.model.does.not.work.and.one.has.atomic.
clusters.that.are.either.electron.deicient.or.hypervalent..Often.it.is.dificult.to.predict.
the.multiplicity.of.the.ground.state..In.addition,.the.widely.popular.Mulliken.popula-
tion.analysis.tends.to.predict.the.incorrect.electron.charge.distribution.in.atom.pairs,.
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