详解calculate xrd powder patterns计算粉末图.pdfVIP

CalculateXRDPowderPatterns

Onceyouhavethedesiredcrystalstructureeitherloadedfromastructurefileordatabaseorentered

bykeyboard,youarereadytocalculateitsXRDpowderpattern.Thispowderpatternisfirstofall

representedbyalistofpossiblereflectionswiththeirintegratedintensitiesI(hkl)calculatedusingthe

equation:

I(hkl)=KLpTAGmF^2

where

KisascalingconstantrelatedtotheintensityofX-raybeam.Sinceitsusuallyanunknown,I(hkl)is

normalizedtothestrongestreflectioninthelistandreportedasrelativepercentageI%.ThisI%is

thenidentifiedasI(f)forfixed-slitgeometry,andasI(v)forvariable-slit(i.e.theta-compensatingslit)

geometry.

LpistheLorentzandpolarizationfactorwhichisdependentonthediffractiongeometryspecified

ontheCalctab:

Lp=(1+Pcos(2)^2)/sin()/sin(2)Bragg-BrentanoDiffractometry(Fixed-Slit),

Debye-ScherrerCamera.

Lp=(1+Pcos(2)^2)/sin(2)Bragg-BrentanoDiffractometry(Variable-Slit),

Debye-ScherrerCamera.

Lp=(1+Pcos(2)^2)/sin()/sin(4)SymmetricGuinier(Frontor

Back-Reflection)Camera.

Lp=(1+Pcos(2)^2)/sin()/cos(2)/sin(2)AsymmetricGuinier,Seemann-Bohlin

Diffractometry.

Lp=(1+Pcos(2)^2)/sin()FlatImagePlatewithintegralrings(plete

diffractioncones).

where2isthediffractionangleofareflectionwithMillerindices(hkl),PistheX-raypolarization

parameteryoucanspecifyonthesimulationdialog,andisthebeam-inclinationanglefromthe

centeroffocusingcircleforasymmetricGuinierdiffractometry.Youcanviewtheschematicsof

thesediffractiongeometriesandtheircorrespondingLpcurvesbyclickingtheicon,asillustrated

below:

Youcanseethechangeofdiffractionconesasafunctionof2anglessimplybymovingthemouse

pointerintheLpplot.FortheGuinierCameraLPgeometry,additionaloptionsareaccessiblefor

thefront(transmission)orback(reflection)setupaswellasthebeam-inclinationangle,asshown

below:

NoticethatallconstanttermsintheLpareomittedfromtheformulasinceonlythe2dependency

mattersincalcu