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(1DepartmentofPhysics,SouthChinaUniversityofTechnology,Guangzhou510640,China;2StateKeyLaboratoryofLuminescentMaterialsandDevices,SouthChinaUniversityofTechnology,Guangzhou510640,China;3NanostructureInstituteforEnergyandEnvironmentalResearch,DivisionofPhysicalSciences,SouthUniversityofScienceandTechnologyofChina,Shenzhen518055,China;4TheoreticalChemistry,ChemicalCentre,P.O.Box124,S-22100Lund,Sweden)Bymodelanalysisandthefirst-principlescalculations,wehaveperformedasystematicinvestigationofhydrogenatedsiliconnanocrystals(H-SiNCs)withvarioussize,shape,andsurfacereconstruction.WedemonstratedthatH-SiNCswiththesmallestH/Siratioareenclosedby(lll)facetsbeforereconstruction,andtwotypicalsurfacereconstructionswilldramaticallydecreasetheH/Siratio,involvingdimersandstepson(lOO)and(lll)facets,respectively.Withthefirst-principlescalculations,wedeterminedthestableH-SiNCs(upt0200Siatoms)andfoundthatthesurfacemorphologiesvarywiththesizeandhydrogenchemicalpotential.Inaddition,wealsostudiedtheelectronicpropertiesofH-SiNCsfocusedonthegapvariationsandchargedistributionsasafunctionofsize,shape,andsurfacereconstruction.ThedimerandstepreconstructionsnotonlybringsignificantdecrementofthegapvaluesandtheH/Siratio,butalsomodulatethechargedistributionsandinducethespatialseparationofnear-gaplevels. |
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