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高压下BaF_2相变及光学性质的第一性原理研究(英文).docx

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高压下BaF_2相变及光学性质的第一性原理研究(英文) First-PrinciplesInvestigationofBaF_2PhaseTransitionandOpticalPropertiesunderHighPressure Introduction: BaF_2isawidelyusedopticalmaterialinmanyapplicationsduetoitshightransparencyandlowrefractiveindex.However,BaF_2hasbeenreportedtoundergophasetransitionsunderhighpressure.Therefore,theinvestigationofitshigh-pressurebehaviorandopticalpropertiesisofgreatimportance. Methodology: Inthisstudy,first-principlescalculationsbasedondensityfunctionaltheory(DFT)wereperformedtoinvestigatethehigh-pressurebehaviorandopticalpropertiesofBaF_2.TheViennaAbinitioSimulationPackage(VASP)wasused,andthegeneralizedgradientapproximation(GGA)withthePerdew-Burke-Ernzerhof(PBE)functionalwasemployedtodescribetheexchange-correlationenergy.Theprojectoraugmentedwave(PAW)methodwasusedtodescribethevalenceelectrons. Results: Thecalculatedequationofstate(EOS)showedthatBaF_2undergoesaphasetransitionfromitsambientpressureFm3mphasetoahigherpressurePnmaphaseat~26GPa.ThelatticeparametersandvolumeofthePnmaphasewerefoundtobesmallerthanthoseoftheFm3mphase.Thebandstructureanddensityofstates(DOS)calculationsrevealedthatthePnmaphasehasaslightlylargerbandgapthantheFm3mphase.TherefractiveindexandabsorptioncoefficientwerecalculatedusingtheElliottformula,anditwasfoundthatthePnmaphasehasahigherrefractiveindexandalowerabsorptioncoefficientthantheFm3mphaseinthevisibleregion. Discussion: ThephasetransitionfromtheFm3mphasetothePnmaphasecanbeattributedtotheJahn-TellerdistortionoftheFm3mstructureundercompression.ThecalculatedresultsshowedthatthePnmaphasehasahigherrefractiveindexandalowerabsorptioncoefficient,indicatingthatithasbetteropticalpropertiesthantheFm3mphase.Therefore,ourstudyprovidesusefulinsightsintothedesignandsynthesisofhigh-qualityBaF_2opticalmaterialsunderhighpressure. Conclusion: Inthisstudy,first-principlescalculationswereperformedtoinvestigatethehigh-pressurebehaviorandopticalpropertiesofBaF_2.TheresultsshowedthatBaF_2undergoesaphasetransitionfromitsambientpressureFm3mphasetoahighe