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1、ABeginner’sGuidetoMaterialsStudioandDFTCalculationswithCastepP.Hasnip(pjh503@york.ac.uk)September18,2007MaterialsStudiocollectsallofitsfilesinto“Projects”.We’llstartbycreatinganewproject.1Nowwe’vegotablankproject,andwewanttodefineasimulationcelltoperformaCastepcalc
2、ulationon.Firstweadda“3DAtomisticdocument”.23We’regoingtostartbysimulatinganeightatomsiliconFCCcell,sorenamethefileac-cordingly.Firstwe’llcreatetheunitcell.45ThedefaultisspacegroupP1,i.e.nosymme-try.Siliconhasthediamondstructure(spacegroupFD3M).BytellingMaterialsS
3、tudiothissymmetryitwillautomaticallyapplyittotheatoms,thusgeneratingatomsatthesymmetrypoints.6Nowtoaddthelatticeconstant–clickonthe“Lattice”tabnearthetopofthe“BuildCrystal”window.SinceFD3Miscubic(FCC)MaterialsStudioknowsonlyahastobeset,andtheanglesandotherlattice
4、constantsaregreyed-out.Enter“5.4”,andthenclickon“Build”.7Nowwe’lladdasinglesiliconatom...8Addasiliconatomattheorigin,bychang-ingthe“element”fromitsdefaultandclick-ing“Add”.Bydefaulttheco-ordinatesareinfractionals,butyoucanchangethisonthe“Options”tab.9Sincewe’dalr
5、eadytoldMaterialsStudiowhatthesymmetryofthecrystalwas,oursinglesil-iconatomisreplicatedateachsymmetrysiteandwenowhaveashinyneweight-atomsili-conunitcell.Youcanrotatetheviewbyholdingdowntheleftorrightmousebuttonanddragging,ormoveitbyholdingdownthemiddlebutton.Uset
6、hemousewheel,orboththeleftandrightbuttonssimultaneously,tozoominandout.10Bydefaulttheatomsareshownaslittlecrosseswithlinesforbonds,andsiliconatomsarecolouredbrownishorange.Youcanalwayschangethisifyoudon’tlikeit.The“bonds”arejustguessesmadebyMaterialsStudiobasedon
7、theele-ment’stypicalbond-lengths.We’renowreadytorunCasteptofindthegroundstatechargedensity.ClickontheCastepicon,whichisasetofthreewavylines(torep-resentplane-waves),andselect“Calculation”.11MaterialsStudiooffersahigh-levelinterfacetoCastep,withcut-offenergy,k-points
8、ampling,convergencetolerancesetc.allsetbythesin-glesetting“Quality”.We’lllookathowtospecifythesethingslater,butfornowwe’lljustdoaveryquick,roughcalculationofth
