wurger,from coherent tunneling to relaxation dissipative quantum--dynamics of interacting defects

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1、2.TunnelingofaSingleDefect2.1EnergySpectrumandTunnelingStatesSubstitutionaldefectsinalkalihalidesprovideamodelsystemforthestudyofquantumtunnelinginacrystallineenvironment.AsexampleswenoteLi,CN,andOHinpotassiumchlorideandsimilarcrystals.Tunnelingarisesfromdefectswhichdonotfitproperlyint

2、hesitesofferedbythehostlattice.Thepotentialexperiencedbythedefectionismainlydeterminedbythesymmetryofthehostcrystal.Potassiumchlorideshowsafccstructurewithtwopositiveionsperunitcell;nearest-neighborpotassiumsitesareatadistanceof4.5/~.Theionicradiusofalithiumdefect,rLi----0.60~.,isbyafa

3、ctoroftwosmallerthanthatofthepotassiumionforwhichitsubstitutes,rK=1.33/~;thusthecageformedbythesixnearestchlorideionsistoolargeforalithiumion.WhereasthelatticevertexconstitutestheenergeticallymostfavorablepositionforK+,thesmallerlithiumionencountersamore7Fig.2.1.Off-centerposi-tionsofa

4、LithiumimpurityinKC1.Ionradiiarereducedbyafactorofg1forvisibility.Open,hatched,andfullcir-clesrepresentC1,K,andLi--ions,respectively.Thesmall.cubeindicatestheeightLi,{~"(positions;thearrowshows9thedirectionofthedipolef,~moment.BycourtesyofM.k)Tornow[99]2.TunnelingofaSingleDefect2.1Ene

5、rgySpectrumandTunnelingStatesSubstitutionaldefectsinalkalihalidesprovideamodelsystemforthestudyofquantumtunnelinginacrystallineenvironment.AsexampleswenoteLi,CN,andOHinpotassiumchlorideandsimilarcrystals.Tunnelingarisesfromdefectswhichdonotfitproperlyinthesitesofferedbythehostlattice.T

6、hepotentialexperiencedbythedefectionismainlydeterminedbythesymmetryofthehostcrystal.Potassiumchlorideshowsafccstructurewithtwopositiveionsperunitcell;nearest-neighborpotassiumsitesareatadistanceof4.5/~.Theionicradiusofalithiumdefect,rLi----0.60~.,isbyafactoroftwosmallerthanthatofthepot

7、assiumionforwhichitsubstitutes,rK=1.33/~;thusthecageformedbythesixnearestchlorideionsistoolargeforalithiumion.WhereasthelatticevertexconstitutestheenergeticallymostfavorablepositionforK+,thesmallerlithiumionencountersamore7Fig.2.1.Off-centerposi-tionsofaLithiumimpurityinKC1.Ionradiia