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1、CharacteristicfeaturesofanharmoniceffectsinthelatticedynamicsoffccmetalsM.I.Katsnelson1,A.V.Trefilov2,andK.Yu.Khromov2.1InstituteofMetalPhysics,UralsBranchoftheRussianAcademyofSciences,620219Ekaterinburg,Russia2RussianResearchCenter”KurchatovInstitute”,123182Moscow,Russ
2、iaAbstractThedispersionintheentireBrillouinzoneandthetemperaturede-pendence(rightuptothemeltingtemperature)oftheanharmonicfrequencyshiftandphonondampinginanumberoffccmetalsisinvestigatedonthebasisofmicroscopiccalculations.Itisfoundthattheanharmoniceffectsdependsharplyo
3、nthewavevectorinthedirectionsΓ-X,X-W,andΓ-Land,incontrasttobccmetals,themagnitudeoftheeffectsisnotduetothesoftnessoftheini-tialphononspectrum.Itisshownthattherelativefrequencyshiftsandthephonondampingnearmeltingdonotexceed10-20%.Therelativeroleofvariousanharmonicproces
4、sesisexamined,andtherelationbetweentheresultsobtainedandexistingexperimentaldataisdiscussed.Theinvestigationofanharmoniceffects(AEs)inlatticedynamicsisaclassicproblemofsolid-statephysics.Itisimportant,specifically,becauseoftherolethatsucheffectstheycanplayinphenomenaasso
5、ciatedwithstructuralphasetransitionsandmeltingincrystals(see,forexample,Refs.1-3).Atthesametime,obtaininganyinformationaboutthemagnitudeandscaleofAEsfromexperimentandtheoryisadifficultproblem.Theexperimentalstudyofsuch”basic”AEsasthefrequencyshiftanddampingofphononsisve
6、rydifficultarXiv:cond-mat/0006205v113Jun2000andleadstoalargeuncertaintyintheresults(see,forexample,thedatapresentedinRefs.4and5forbccandfccmetals,respectively).Uptonowfirst-principlesmicroscopiccalculationsofAEshavebeenperformedforonepointoftheBrillouinzone(N)inthebccpha
7、seofZrandfourpoints(N,P,ω,G)inMo.(Ref.6)DetailedinformationaboutAEsintheentireBrillouinzoneandtheirtemperaturedependencehasbeenobtainedinRefs.4and7onthebasisofpseudopotentialtheoryforthebccphasesofalkaliandalkaline-earthmetals.Forthesemetalsthemoststrikingmanifestatio
8、nsofAEsareduetothe”soft-modebehavior”(theanomaloustemperaturedependenceofthephononfrequencies)oftheΣ4branch.Itisofinterestto