全国功能材料量子设计和量子物理研究生培训

全国功能材料量子设计和量子物理研究生培训OverviewofComputationalMaterialsScienceFirst-principles(abinitio)Method

basicconceptsandapproximationsparallelimplementationedgedislocationinSiMolecularDynamicsSimulation

carbonnanotubesMesoscopicSimulation

self-assembly/self-organizationofquantumdotsquantumwiresOutline第二页，共41页。Experiment---Theory---ComputationTheoryNewtonianmechanicsStatisticalmechanicsQuantummechanicsComputationnanoscopicAtomisticElectronicExperiment第三页，共41页。AdvanceofComputerPower(FromF.F.Abraham)第四页，共41页。MissionToexplorethevariousmaterialspropertiesbycomputationalmodelingandsimulationPhysicalmodel+algorithmmaterialsproperties第五页，共41页。ObjectiveNotonlytoelucidateexistingexperimentalresultsbutalsotopredictnewmaterialsandnovelmaterialspropertiestobeexploredbyexperimentsETC第六页，共41页。Self-assemblyandself-organizationofNanostructures(quantumdotsandquantumwires)Nanofabrication:MechanicalpropertiesofnanoscalethinfilmsandofcarbonnanotubesNanomechanics/nanomechanicalarchitecture:Computationaldesigningofnanoscalethin-filmandCNTdevices(sensors,switches,…)Nanoelectronics:First-principlessimulationofAFMandSTMimagingNanoimaging:NanoclusterengineeringofcatalyticsurfacesNanocatalysis:Current&Near-FutureResearchTopics第七页，共41页。ComputationalSoftware(theory/modeling/simulationpackages)First-principlesandempiricalelectronicandatomicsimulationsofstructural,dynamic,mechanical,electronic,transportandmagneticpropertiesofnanomaterialsandnanodevicesNanoscopicsimulationsofgrowthandformationofthinfilmsandnanostructuresandself-assembly/self-organizationofquantumwiresandquantumdotsAnalyticaltheoryandcontinuummodelofnanostructuresandnanomechanics第八页，共41页。ComputationalHardware(in-houseBeowulfclusters)I/ORouterSimple-Construction---Cost-effective---Expandable第九页，共41页。VISCOComputationalInterface(VisualInteractiveScientificcomputing)VISCOWeb-BasedvisualizationinterfacecomputingResearch/EducationApplications:Provideaweb-basedvisualandinteractiveplatformforcomputationProvideacomputationalserverforabroadrangeofusers,(expertsornon-experts)Goscience,engineering,andbeyond第十页，共41页。SimulationatDifferentLengthScalesE=E({Ri})fi=dE/dRi

(short-range)Equationofmotionofatoms{Ri}AtomicE=E({Li})fi=dE/dLi

(long-range)Equationofmotionofboundaries{Li}Mesoscopic第十一页，共41页。ComplexitiesofInteratomicPotentialsAbInitio(First-principles)Methods:Etot=Eele-ele+Eele-ion+Eion-ionInput:atomicspeciesSemi-Empirical(Classical)Methods:Etot=V2(R1-R2)+V3(R1,R2,R3)+…Input:potentialparameters第十二页，共41页。ComparisonofAtomicSimulationMethodsmethod abinitio

empiricalmechanics quantum classical

electroniceffect yes no/approximate accuracy good fairefficiency fair good(systemsize) (10-103) (102-108)第十三页，共41页。SimulationofMaterialsPropertiesEnergetics:

cohesiveenergy,bondingenergy...StructuralProperties:

crystalstructure,bondingconfiguration...ElasticProperties:

modulus,elasticconstants,straindistribution...ElectronicProperties:

bandstructure,chargedensity…DynamicProperties:

latticedynamics,phasetransition...第十四页，共41页。SimulationofDifferentMaterialsSystemsPointandExtendedDefectsThinFilms,Surfaces,andInterfacesMoleculesandClustersBulkMaterials第十五页，共41页。CombineSimulationsatDifferentLengthScalesThermodynamicSimulationKineticSimulationMechanicalSimulationAbInitioBondingEnergies

DiffusionBarriersElasticConstants第十六页，共41页。MultiscaleSimulationContinuumClassicalAbinito第十七页，共41页。EdgeDislocationsinSiAlarge-ScaleAbInitioAtomicSimulationbyparallelcomputing第十八页，共41页。PseudopotentialTotal-EnergyMethodDensityFunctionalTheory:

modelelectron---electroninteractionPseudopotentialTheory:

modelelectron---ioninteractionSupercellTechnique:

modelsystemswithaperiodicgeometryIterativeMinimizationTechnique:

optimizeelectroniccoordinates!ParallelImplementation!第十九页，共41页。DensityFunctionalTheoryInteractingmany-electronproblemSingleelectroninaneffectivepotential1.HohenbergP.andKohnW.,Phy.Rev.136,864B(1964).2.KohnW.andShamL.J.,Phy.Rev.140,1133A(1965)Kohn-ShamEquation:Localdensityapproximation:Structuralparameters:atenthofanÅTotalenergydifference:afewpercentCohesiveenergy:>10%第二十页，共41页。SupercellTechniquePeriodicboundaryconditionPlane-wavebasisexpansion第二十一页，共41页。AllelectronValenceelectronStrongionicpotentialWeakpseudopotentialPseudopotentialTheoryrpsVpsyaeyrZ第二十二页，共41页。Matrixdiagonalizationcpu~Np3IterativeMinimizationConventionalapproach:1.CarR.andParrinelloM.,Phy.Rev.Lett.55,2471(1985)Matrixmultiplicationcpu~Nb2NpIterativeapproach:第二十三页，共41页。ParallelImplementationPlane-waverepresentation:1.Clarke,Stich,andPayne,Comp.Phys.Comm.72,14(1992)Distributingthecomplexarray:第二十四页，共41页。ComputationalTechnicalDetailsLocalDensityApproximation:

Ceperley-AlderformforexchangeandcorrelationPseudopotential:Kerker’snorm-conservingpseudopotentialSupercell:Plane-waveenergycutoffof8ryd.Twospecialk-pointstosampleBrillouinzoneIterativeMinimization:Preconditionedconjugate-gradientmethodParallelComputing:128nodesonIntelParagon第二十五页，共41页。ParallelSupercomputer+AdvancedAlgorithmLarge-ScaleAbInitioModelingandSimulation1.90opartialdislocation,Biggeretal,PRL,69,2224(92).2.ScrewDislocation,AriasandJoannopoulos,PRL,73,680(1994)第二十六页，共41页。MotivationTocarryoutalarge-scaleabinitiocalculationofedgedislocationsinSi,usingparallelcomputingElasticPropertiesElectronicPropertiesMechanicalBehaviorDevicePerformance第二十七页，共41页。(a/2)[110]EdgeDislocationinSiXTEM(M.Chisholm)ball-n-stickmodel-[110]projection第二十八页，共41页。ModelSystem:a/2<110>edgedislocation[110]projectionofdiamondSilattice-第二十九页，共41页。DislocationCoreFormation:iif第三十页，共41页。Supercell:Dislocationdipole[110]projectionofa128-atomunitcell-第三十一页，共41页。StrainEnergy:

periodiclatticesummationd2duvEc~coreenergycoefficient,rc~coreradiusb(r)~Burgersvector,K~elasticconstant,第三十二页，共41页。Properties:corestructure,coreenergy,strainfield,interactionenergy,electronicstructureSystemSizes:64atoms128atoms256atoms400atoms576atoms64atoms256atoms576atoms第三十三页，共41页。CoreStructure:MaximumDeviationinBondLengthNo.ofringsofseparationD%第三十四页，共41页。CoreStructure:MaximumDeviationinBondAngleNo.ofringsofseparationD%第三十五页，共41页。StressintheCore:MaximumAtomicLevelStressNo.ofringsofseparationsii(eV/Å3)第三十六页，共41页。DislocationStrainEnergyEc=0.75eV/Å,rc=4.1Å第三十七页，共41页。ElectronicStructureZXYKzKyKx400