Chemistry Reference
In-Depth Information
19.34 Å
3.8
Å
Sixfold
Disorder
19.34 Å
Five- to sixfold
FIGURE 5.15  Illustration.of.removal.of.atoms.from.perfectly.ordered.hexagonal.arrange-
ment. in. 2D,. followed. by. disordering. to. obtain. an. arrangement. with. remnant. order,. as. a.
model.for.the.in-plane.structure.of.the.surface.layers.seen.in.the.ab.initio.MD.simulations.of.
Na..(Adapted.with.permission.from.Walker,.B.G..et.al.,. J. Chem. Phys .,.127,.134703,.2007,.
American.Institute.of.Physics.)
5.5  SUMMARY
In. this. chapter,. we. have. discussed. the. properties. of. liquid. metal. surfaces,. focus-
ing. particularly. on. characterization. and. understanding. of. surface. structure. from.
computer. simulations. and. experiments.. The. liquid. surfaces. of. metals. demonstrate.
the.interesting.phenomenon.of.surface-induced.layering;.this.has.been.irmly.estab-
lished. on. the. basis. of. simulations—the. most. accurate. being. quantum. mechanical.
simulations. based. on. density. functional. theory—as. well. as. extensive. x-ray. relec-
tivity. measurements.. At. least. three. formation. mechanisms. were. suggested. on. the.
basis.of.earlier.simulation.work..These.were.assessed.by.more.recent.simulations.on.
liquid.sodium.surfaces.using.the.rigorous.ensemble.density.functional.theory.tech-
nique..Combining.simulations.of.the.free.liquid.surfaces.of.sodium.with.computer.
“experiments”.(e.g.,.simulation.of.the.liquid.in.contact.with.a.ixed.layer.of.sodium.
atoms).favors.the.explanation.that.the.rapid.decay.of.the.electronic.density.across.the.
free.surface.or.liquid-vapor.interface.acts.like.a.hard.wall,.geometrically.conining.
the.electrons.and.resulting.in.the.formation.of.atomic.layers..Friedel.oscillations.as.
potentially.driving.layer.formation.was.ruled.out.by.the.observation.of.layers.when.
a.rigid.layer.is.inserted.into.the.bulk.liquid..Friedel.oscillations.were.seen.at.solid.
surfaces. of. sodium. (an. observation. similar.to. that. seen. for. Mg(10 0). earlier. [45]);.
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