lecture04.pdf

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TheNutsandBoltsofFirst-PrinciplesSimulationDurham,6th-13thDecember20014:

TheNewCASTEPCASTEPDevelopersGroupwithsupportfromtheESFkNetworkNewCAmbridgeSerialTotalEnergyPackageAnintroductionTheNutsandBoltsofFirst-PrinciplesDurham,6th-13thDecember2001Lecture4:

NutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

3WhatNewCASTEPisnot?

ItsnotjustCAmbridge?

ItsnotjustSerial?

ItsdoesntjustcalculateTotalEnergies?

However,itisstillaPackage!

NutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

4So,WhatisitThen?

IntroductiontotheCASTEPDevelopersGroup?

ThegoalsoftheNewCASTEPproject?

AbriefhistoryofNewCASTEP?

Thefeaturesofthepackage?

Howtousethecode（commandline）?

Philosophyanddesignofthecode?

ThefutureofNewCASTEPNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

5TheCASTEPDevelopersGroup?

MikePayne（Cambridge）?

MattProbert（York）?

ChrisPickard（Cambridge）?

StewartClark（Durham）?

PhilHasnip（Cambridge）?

PhilLindan（KentatCanterbury）?

MattSegall（Cambridge,CamitroUKLtd.）NutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

6TheGoalsofNewCASTEP?

Easeofmaintenance?

Easeoffuturedevelopment?

Portability?

EfficiencyThesegoalsaresometimesconflicting,thereforeacompromisemustbefoundNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

7ABriefHistoryofNewCASTEP?

July99:

Ameetingofinterestedparties.IsthereaneedforanewPWpseudopotentialcode?

July99-Jan.00:

Informalspecificationgroupoutlinesthespec.ofanewcode.?

Feb.00:

Implementationofnewcodebegins.CDGformed.?

May01:

AgreementreachedwithMSI（NowAccelrys）tocommercialiseNewCASTEP.?

Dec.01:

CodefreezeonfirstversionofNewCASTEP.NutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

8NewCASTEPFeatures?

Parallel,portablecode?

GeometryOptimisation?

BFGS?

DampedMD?

MolecularDynamics?

NVE?

NVT?

LinearResponseforPhononspectraNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

9CASTEPFeaturesContinued?

Transitionstatesearch?

LST/QST?

Electronicproperties?

OpticalSpectra?

DOS?

PopulationAnalysisNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

10CASTEPTechnicalFeatures?

Ultrasoft/Norm-conservingpseudopotentials?

Pseudopotentialgenerationon-the-fly?

Doublegridtechniqueforcharge/potentialgrid?

Multipleelectronicminimisers?

All-bandsCG?

RMM/DIISNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

11TechnicalFeaturesCont?

Metalstreatedby?

Densitymixing?

EnsembleDFT?

Exchange-CorrelationPotentials?

LDA?

Perdew-Wang91GGA?

PBE/RPBEGGA?

Non-linearcorecorrectionsNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

12HowtoUsetheCode:

TheCellFile!

ExamplecellfileforprimitiveSiC%blockLATTICE_ABC3.0745003.0745003.07450060.060.060.0%endblockLATTICE_ABC%blockPOSITIONS_FRACSi0.00000.00000.0000C0.25000.25000.2500%endblockPOSITIONS_FRACNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

13MoreCellFileKeywordsKPOINTS_MP_GRID444%blockSYMMETRY_OPS%endblockSYMMETRY_OPS%blockSPECIES_POTCmy_C_pot.usp%endblockSPECIES_POTNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

14ControllingtheCalculation:

TheParameterFileTask:

GeometryOptimizationXC_functionalPW91Basis_precisionPreciseElectronic_minimiserCGElec_energy_tol=0.000001eVNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

15MoreParametersGeom_methodBFGSGeom_force_tol:

0.01hartree/bohrFix_occupancies=TRUEContinuation=my_last_run.checkEnergy_unit=kcal/molNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

16ExampleOutputSummaryofcellandparametersinput-SCFSCFloopEnergyEnergygainTimer-SCFperatom（sec）-SCF-SCFInitial6.99675047E+0024.22-SCF1-8.56371636E+0021.94505835E+00223.70-SCF2-8.57260747E+0021.11138925E-00142.59-SCF3-8.57286394E+0023.20580434E-00362.00-SCF4-8.57286462E+0028.55207285E-00680.91-SCF5-8.57286463E+0023.12287085E-00898.20-SCF-tokineticenergycontributioncallwave_add（wvfn_temp,H_wvfn）!

Applythenon-localpotentialtothewavefunctioncallnlpot_apply（wvfn,wvfn_temp）!

AddVnl|psitogetfinalH|psicallwave_add（wvfn_temp,H_wvfn）NutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

27CodingStyle?

Clearcode?

Meaningfulvariableandsubroutinenames?

Lotsofcomments?

Goodstructure?

Carewithperformanceissues?

SomefeaturesofFORTRAN90sub-optimal?

UseBLAS/LAPACKwhereapplicableNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

28ExampleproblemwithF90!

Findingthetraceofasub-arrayreal,dimension（N,N）:

A!

Passasub-arrayofAofdimensionmtr=bad_trace（A（1:

m,1:

m）,m）!

Passthewholearraywithdimensionofsub-arraytr=good_trace（A,m,N）NutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

29Timingsforbad_traceNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

30Timingsforgood_traceNutsandBolts2001Lecture4:

IntroductiontoNewCASTEP?

31TheFutureofNewCASTEP?

NPTMolecularDynamics?

Free-energyintegrationforreactionbarriers?

Newnon-localXCfunctionals?

NMRchemicalshifts?

EELS?

Ramanspectro