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1、ressureInducedHydrogenressureInducedHydrogenDominantMetallicStateDominantMetallicState压力力诱导氢占主占主导地位地位的金属状的金属状态ContentsIntroduction theoretical prediction of hydrogen under high pressure why hydrides previous studies on AlH3Experimental methodResult & discussionSummaryHydrogenInteresting physical pro
2、pertiesMetallic conductivity High-temperature superconductivity Tc room temperatureMolecular hydrogenHydrogen dense stateexperimentally difficult.Theoretical predictionMore than 400500 GPa is required.under high pressurehydridesInterstitial hydridesCovalent hydridesM: rare earth metalM: Al, Si.The M
3、-H bonding is covalent.Insulator at ambient pressureHydrogen atoms are in the interstitial site of metal lattice.For the model of dense metallic hydrogen, hydrides (for example MHx) are paid attention.hydridesMHx ; YH3, AlH3Hydrogen molecular is contained 1.5 mol per 1.0 mol of M.Hydrogen in MHx is
4、precompressed at ambient pressure.The partial hydrogen volume in MHx That volume in H2.At much lower pressure, hydrogen dense metallic state could be observed.引去Hydrogen atomic volume in MHx from subtraction of atomic volume of M.AlH3R-3c structure Two AlH6-units share this H atom.AlH6 octahedrons l
5、inked by Al-H-Al bridgesThe partial hydrogen volume per H atom in AlH3 (5.5 A3) is smaller than that in H2 (7.5 A3).Hydrogen in AlH3 is precompressed !P ambient pressureHH Al-H distance: 1.7 A H-H distance: 2.5 A Volume per formula unit in AlH3: 33 A3Previous studies on AlH3P 100 GPa)Purpose of this
6、 experiment the insulator to metal transition in AlH3To observe the crystal structure under high pressure X-ray diffraction measurement electrical resistance measurementwere performed under high pressure.Experimental methodl X-ray diffraction measurement ( at European Synchrotron Radiation Facility)
7、 ( P 110 GPa , T = 300 K)l Electrical resistance measurement ( P 164 GPa , 4 K T 100 GPaAl-H distance: 1.72 H-H distance: 1.54 At 110 GPa,Calculated enthalpy in the R-3C, Im-3m, Pm-3nDiscussionPhase IIIPartial hydrogen volume per H atom in AlH3 at 100 GPa Partial hydrogen volume per H atom in molecu
8、lar hydrogen at 300 GPa.Phase III is a hydrogen dense phase !Equal toResult (electrical resistance) Sample becomes dark. Electrical resistance sharply drops.At 100 GPaAt 120, 164 GPa, on coolingElectrical resistance shows typical metallic behavior.insulator to metal transition SummaryCrystal structureElectrical propertyR-3c63 100insulatormetalP1Pm-3n0P (GPa)At over 100 GPa, Pressure-Induced Hydrogen-Dominant metallic state was observed in AlH3.Hydrogen dense stateThats all. Thank you for your attention. Al-H distance: 1.7 H-H distance: 2.5 结束结束
