Structure of Liquid Metal Surfaces: A First Principles Perspective - Metallic Systems: A Quantum Chemist's Perspective - page 152

the. ixed. layer,. precluding. the. possibility. of. such. atoms. driving. rearrangements.
leading.to.layer.formation.

5.3.3.3 Friedel Oscillations in Sodium
To.ascertain.whether.the.Friedel.oscillations.that.were.observed.at.the.solid.Mg(10 ‾ 0).
surface.in.Ref..[45].persist.at.liquid.metal.surfaces,.the.density.subtraction.procedure.
used.by.Cho.et.al..for.solid.surfaces.was.adapted.to.consider.the.formation.of.a.liquid.
surface.
The. method. of. calculating. the. charge. redistribution. upon. surface. formation. is.
illustrated.in.Figure.5.9.for.a.crystalline.system:.the.valence.electron.density.for.the.
system.in.which.a.surface.has.been.created.is.subtracted.from.the.density.for.the.bulk.
system.in.which.there.is.no.vacuum.region..Valence.charge.density.redistributions.
upon.surface.formation.for.solid.surfaces.of.sodium.are.shown.in.Figure.5.10..Strong.
Friedel. oscillations. are. found. to. exist. in. the. redistribution. of. charge. upon. surface.
formation.for.solid.sodium.surfaces.
A.similar.procedure.was.followed.to.extend.the.study.of.Friedel.oscillations.at.the.
liquid.surface..Though.it.has.been.shown.(for.instance.by.the.work.of.Chacón.et.al..
[46],.Tarazona.et.al..[47],.and.Velasco.et.al..[48]).that.layered.atomic.surface.density.
proiles.can.be.obtained.without.taking.into.account.the.quantum.mechanics.of.the.
electrons,.computation.of.the.response.of.the.electronic.system.to.surface.formation.
requires.an.accurate.quantum.mechanical.treatment..First,.a.series.of.snapshots.were.
taken.from.a.simulation.of.bulk.liquid.sodium.and.a.vacuum.region.was.added.to.

Vacuum

z

Bulk-truncated Bulk

x

FIGURE 5.9 Unit.cells.used.to.calculate.the.charge.redistribution.upon.surface.formation..
The.unit.cell.on.the.left.is.the.“bulk-truncated”.cell.that.contains.a.vacuum.region.and.that.on.
the.right.is.the.bulk.cell.that.contains.no.vacuum.region,.and.so.no.surfaces.