Computational Investigations of Metal Oxide Surfaces - Metallic Systems: A Quantum Chemist's Perspective - page 206

surface. phase. diagrams. dependent. on. temperature. and. partial. pressure. of. oxygen.
and.hydrogen.for.instance,.have.explored.a.variety.of.low.index.surfaces.and.their.
different.terminations. 22 .Additional.work.has.looked.at.details.of.the.surface.atomic.
and.electronic.structure. for.reconstructions. of.this.plane,.which.may.hold.techno-
logical.signiicance. 23,24
As.mentioned,.it.is.often.thin.ilms.rather.than.bulk.crystalline.material.of.metal.
oxides. that. are. important. from. an. application. standpoint,. and. this. may. require. a.
good.model. and.understanding.of.interfacial.interactions.. A.general.review.of.the.
theory. of. metal. ceramic. interfaces. was. provided. by. Finnis. in. 1996. 25 . The. impor-
tance.of.interfaces.is.particularly.appropriate.for.alumina,.which.forms.an.Angstrom.
self-terminating.coating.when.formed.via.Al,.NiAl,.or.Ni 3 Al.oxidation. 26-28 .Jennison.
and.coworkers.performed.several.DFT.studies.of.thin.ilm.alumina.on.various.met-
als.and.determined.that.the.thin.ilm.phase.is.most.similar.to.κ-Al 2 O 3 . 29-31 .A.more.
recent.DFT.study.by.Kresse,.which.included.a.detailed.comparison.to.scanning.tun-
nel.microscope.(STM).experiments,.determined.that.the.alumina.overlayer.structure.
on.bulk.NiAl.(110).had.a.larger.number.of.simulated.atoms.than.in.previous.studies.
and. concluded. that. the. ilm. structure. differed. from. all. bulk. phases. of. alumina. 32 .
Numerous.additional.DFT.studies.of.interfaces.between.α-alumina.and.metals.have.
improved. our. understanding. of. atomic-level. interactions. and. electronic. structure.
modiications.at.these.interfaces. 33-36
Many. of. the. most. recent. DFT. studies. of. α-alumina. surfaces. are. interested. in.
small.molecule.adsorption.with.alumina.serving.as.the.support.rather.than.on.the.
detailed.surface.structure.of.alumina.itself..For.instance,.Casarin.et.al..investigated.
chemisorption. of. CO. on. the. basal. plane. of. alumina. (α-Al 2 O 3 . (0001).). in. 2000. 37 .
Gamallo.and.Sayos.looked.at.atomic.oxygen.and.nitrogen.adsorption.on.the.clean.
UHV.surface.(aluminum.terminated), 38 .and.Hernandez.and.coworkers.compared.the.
adsorption.of.several.metals.on.the.clean.surface. 39 .In.2005,.Chatterjee.and.cowork-
ers.explored.the.deposition.of.Ag.on.the.basal.plane.of.alumina.while.attempting.to.
account.for.the.complexity.of.this.surface.in.non-UHV.conditions. 40 .Similarly,.Yang.
and. Rendell. modeled. adsorption. of. Ga. on. clean. alumina 41 . and. surfaces. contami-
nated.through.hydrogen.chemisorption.and.physisorption. 42 .Recently,.DFT.studies.
intending.to.model.larger.molecule.chemisorption,.such.as.quinizarin, 43 .nitrometh-
ane,. and. 1,1-diamino-2,2-dinitroethylene, 44 . the. luorination. of. dichloromethane, 45 .
uranyl. (hydrated), 46 . Pd. nanoclusters, 47 . and. ZnO. growth 48 . on. α-Al 2 O 3 . (0001). have.
been.undertaken.
Calculations.of.alumina.surfaces, 49 .adsorption.on.alumina.surfaces,.and.with.alu-
mina. surfaces. serving. as. a. support. have. begun. to. focus. on. γ-Al 2 O 3 ,. which. is. fre-
quently.a.more.relevant.phase.due.to.experimental.growth.conditions,.temperatures,.
and.pressures..Because.of.computational.size.constraints,.it.is.common.to.see.cluster.
models.employed.instead.of.periodic.models,.when.phases.other.than.α-Al 2 O 3 .are.
modeled;. however,. current. studies. are. able. to. employ. periodic. models. of. γ-Al 2 O 3 ..
Several.recent.studies.have.looked.at.γ-Al 2 O 3 .with.adsorbates.such.as.heavy.metals.
including. Pd, 50 . Pb. (on. hydrated. surfaces), 51 . oxides. of. Ba 52 . and. Mo, 53 . small. mol-
ecules. including. CO. and. C 2 H 4 . on. supported. Pd. clusters, 50,54 . and. MoS 2 . sheets. 55,56 .
Recent.studies.are.able.to.address.adsorption.of.larger.and.more.complex.molecules.
and. reactivity,. such. as. phosphonyl. reagents. on. γ-Al 2 O 3, 57 . chemical. warfare. agents.