Chemistry Reference
In-Depth Information
methods..Remarkable.progress.was.achieved.for.the.calculation.of.nuclear.magnetic.
shielding.tensors.[24].and.excited.states.via.time-dependent.density.functional.the-
ory. (TD-DFT). [25].. The. calculation. of. many. one-electron. properties. like. electro-
static. potentials. [26],. nuclear. quadrupole. coupling. constants. [27],. and. others. was.
realized,.too..A.drawback.of.the.irst.deMon-KS.release,.deMon-KS1,.was.its.rather.
bad.self-consistent.ield.(SCF).convergence..At.that.time,.it.was.not.obvious.if.this.
was.due.only.to.technical.problems.or.if.the.itting.of.the.Coulomb.and.exchange-
correlation.potential.represented.a.fundamental.problem.for.the.SCF.convergence..
However,.it.had.already.been.proven.that.the.energy.gradients.were.not.variational.
due.to.the.least-squares.it.of.the.exchange-correlation.potential.according.to.Sambe.
and.Felton.[28-30].
Triggered.by.these.concerns,.the.original.deMon-KS.version.was.further.devel-
oped.in.Montpellier.by.A..Goursot.and.in.Stockholm.by.L.G.M..Pettersson..A.major.
achievement.was.the.implementation.of.accurate.numerical.integration.algorithms.
for.the.calculation.of.exchange-correlation.potentials..In.this.way,.the.least-squares.
it. could. be. avoided.. However,. the. computational. demands. associated. with. the.
numerical.integration.algorithm.made.this.approach.impractical.for.routine.applica-
tions..Nevertheless,.the.variational.nature.of.the.resulting.gradients.resolved.some.of.
the.basic.problems.encountered.with.deMon-KS1..At.the.beginning,.the.Montpellier.
and.Stockholm.efforts.were.independent.from.each.other..In.1997,.they.merged.into.
the.deMon-KS3.program.version..In.cooperation.with.K..Hermann.from.the.Fritz-
Haber.Institut.in.Berlin,.the.deMon.branch.from.Stockholm.was.further.modiied.for.
the.calculation.of.core-level.spectra..It.is.distributed.under.the.name.StoBe.[31].and.
is.particularly.well.suited.for.the.calculation.of.core-level.spectra.
Independently. from. the. deMon. development,. the. AllChem. [32]. project. was.
started. by. the. group. of. A.M.. Köster. in. Hannover. in. 1995.. The. aim. of. this. proj-
ect.was.to.write.a.well-structured.DFT.code.for.the.further.study.of.auxiliary.den-
sity. approaches. from. scratch.. The. irst. AllChem. calculations. appeared. in. 1997. in.
the.literature..The.structured.programming.of.AllChem.proved.very.useful.for.the.
development.and.testing.of.new.auxiliary.function.DFT.approaches.and.algorithms..
On.the.other.hand,.AllChem.was.used.more.and.more.for.standard.computational.
chemistry.applications..However,.the.primitive.input.structure.made.the.program.use.
rather.cumbersome.and.prone.to.input.errors.
Based.upon.an.initiative.of.D.R..Salahub,.A..Goursot,.and.A.M..Köster,.the.irst.
deMon. developers. meeting. was. held. in. Ottawa. in. March. 2000.. At. this. meeting,.
the.deMon.and.AllChem.developers.agreed.to.merge.their.codes.in.order.to.keep.a.
Tower.of.Babel.from.rising..As.a.result,.a.new.code.that.couples.the.deMon.func-
tionality. and. input. utilities. with. the. stable. and. eficient. integral. and. SCF. branch.
from. AllChem. was. developed.. This. code,. which. was. named. deMon2k. [33],. was.
presented. for. the. irst. time. at. the. third. deMon. developers. meeting. in. Geneva. in.
2002..Over.the.next.3.years,.the.beta.version.of.this.code.was.distributed.and.tested.
within.the.deMon.developers.community..The.annual.meetings.of.this.community.
at.the.deMon.developers.workshops.were.used.to.discuss.the.code.structure.and.to.
exchange.algorithmic.developments.
Since.the.sixth.deMon.developers.workshop.in.2005.in.Dresden,.deMon2k.has.
been.distributed.to.the.public.under.a.license.agreement..The.2.2.6.release.served.
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