Density Functional Calculations of Metal Clusters: Structure, Dynamics, and Reactivity - Metallic Systems: A Quantum Chemist's Perspective - page 334

calculation.of.polarizabilities.presents.its.own.challenges.to.DFT.and.ADFT.meth-
ods.. Here. the. need. to. consider. inite. temperature. effects. (through. BOMD. for. the.
case.of.sodium.clusters).contains.a.lesson.that,.we.believe,.has.considerable.general-
ity..Finally,.the.use.of.DFT.in.the.arena.of.TM.cluster.catalysis.has.been.explored..
The.catalytic.clusters.are.still.very.small.in.these.studies,.and.the.general.reliability.
of. the. methodology. still. requires. further. validation.. Nonetheless,. the. results. most.
likely.provide.valid.insight.into.the.catalytic.mechanisms.
Although.the.ield.has.progressed.greatly.since.the.Xα-scattered.wave.days,.much.
remains.to.be.done..The.currently.available.functionals.are.still.not.entirely.adequate.
for.the.case.of.many-electron,.multi-determinantal.systems.such.as.the.TM.clusters..
Even.the.meta-GGA.and.hybrid.functionals.only.represent.some.sort.of.mean-ield.
approximation..Perhaps.the.future.will.see.a.better.combination.of.DFT.and.wave.
function.methodology;.work.in.this.direction.is.certainly.needed..Although.the.sys-
tems.reviewed.in.this.chapter.have.considerable.complexity,.they.are.all.in.the.“small”.
category.when.one.considers.applications.in.the.main.forefront.areas.of.experimental.
science:.materials.science,.nanoscience,.and.systems.biology..Although.we.have.not.
reviewed.work.in.these.disciplines.in.this.chapter,.many.of.the.deMon.developers.are.
highly.interested.in.the.next.level.of.complexity,.and.considerable.progress.has.been.
made.toward.inding.the.proper.role.for.DFT.and.deMon.within.a.broader.context.of.
multi-method.multiscale.modeling..The.tight-binding.DFT.method,.which.has.been.
implemented. in. deMon2k,. allows. systems. with. up. to. a. few. hundred. atoms. to. be.
treated.(so.far.not.including.TMs).in.full.dynamics.mode..Various.coarse-graining.
approaches. are. being. explored. as. is. QM/MM. methodology. (with. CHARMM. and.
deMon. being. linked,. in. the. irst. instance). as. well. as. QM/QM′. approaches,. which.
combine.real.DFT.with.TBDFT..The.results.of.such.coarse-grained.approaches.will,.
in.the.fullness.of.time,.be.linked.to.even.more.“macroscopic”.approaches,.such.as.
the.kinetic.Monte.Carlo.method,.to.inally.yield.predictions.on.rate.processes.that.
have.DFT.results.at.the.heart.of.the.methodology,.but.also.have.the.other.techniques.
that.are.needed.for.a.full.description.of.the.complex.systems.
We. hope. that. this. personal. overview. will. give. the. reader. a. sense. of. what. has.
been.accomplished.in.the.area.of.DFT.calculations.for.metal.clusters.over.the.last.
two. decades. or. so.. More. importantly,. we. hope. that. some. readers. will. rise. to. the.
challenge. of. taking. the. theory. to. the. next. level,. either. along. some. of. the. lines.
.mentioned.in.the.previous.paragraph.or.along.other.directions.that.have.not.been.
listed. or. have. not. been. thought. of. yet.. We. think. the. next. decade. will. be. a. most.
exciting.one!

REFERENCES
. 1.. R.. G.. Parr,. W.. Yang,. Density-Functional Theory of Atoms and Molecules, . Oxford.

University.Press,.New.York.(1989).

. 2.. R.. M.. Dreizler,. E.. K.. U.. Gross,. Density Functional Theory ,. Springer-Verlag,. Berlin.

(1990).

. 3.. M.. Levy,. J.. P.. Perdew,. Density Functional Methods in Physics ,. Plenum,. New.York.

(1985).