Qhov Tseem Ceeb - Bragg vs Laue Diffraction
Bragg thiab Laue diffractions yog cov cai siv los piav qhia X-ray diffractions hauv cov txheej txheem crystallographic. Bragg txoj cai yog ib rooj plaub tshwj xeeb ntawm Laue diffraction. Laue diffraction (los yog Laue equation) hais txog kev tawg ntawm nthwv dej hauv cov txheej txheem ntawm diffraction los ntawm ib lub siv lead ua. Qhov sib npaug Laue tau muab npe tom qab Max Von Laue (1879-1960). Bragg txoj cai, ntawm qhov tod tes, muab cov ces kaum rau coherent thiab incoherent scattering los ntawm ib tug siv lead ua lattice. Qhov sib txawv tseem ceeb ntawm Bragg thiab Laue diffraction yog Bragg diffraction muab cov ces kaum rau coherent thiab incoherent scattering los ntawm ib tug siv lead ua lattice whereas Laue diffraction hais txog qhov tawg ntawm nthwv dej nyob rau hauv tus txheej txheem ntawm diffraction los ntawm ib tug siv lead ua.
Bragg Diffraction yog dab tsi?
Bragg diffraction muab cov ces kaum rau coherent thiab incoherent scattering los ntawm ib tug siv lead ua lattice. Cov txheej txheem crystallographic suav nrog qhov xwm txheej ntawm X rays ntawm cov siv lead ua lattices thiab soj ntsuam yoj tawg. Thaum X rays tawg los ntawm ib lub lattice siv lead ua, Bragg txoj cai piav txog lub kaum sab xis uas X-ray beams tshwm sim los ntawm cleavage ntsej muag ntawm cov siv lead ua. Lub kaum sab xis pom ntawm no yog hu ua theta (θ).
Bragg's Equation
Txoj cai Bragg tuaj yeem muab tau raws li hauv qab no.
nλ=2d sinθ
Ntawm no, d yog qhov kev ncua deb ntawm atomic txheej ntawm cov siv lead ua lattice. Nws tseem hu ua lattice spacing thiab yog qhov sib txawv tsis sib xws (nws txawv raws li hom siv lead ua). Lambda (λ) kuj yog qhov sib txawv, thiab nws yog lub wavelength ntawm qhov xwm txheej X ray beam. θ yog lub kaum sab xis. Lub cim "n" sawv cev rau tus lej. 2d sinθ muab txoj hauv kev sib txawv ntawm ob lub nthwv dej uas muaj kev cuam tshuam zoo.
Daim duab 1: Bragg Diffraction Planes
Lub Braggs diffraction tshwm sim thaum lub lattice sib nrug ntawm cov siv lead ua piv nrog qhov xwm txheej X ray beam. Ntawm no, X-ray beam yuav tsum tau tawg los ntawm cov atoms ntawm lub lattice nyob rau hauv ib txoj kev specular (daim iav zoo li xav txog ntawm ib qho chaw), thiab cov nqaj tawg yuav tsum muaj kev cuam tshuam.
Laue Diffraction yog dab tsi?
Laue diffraction (los yog Laue equation) hais txog kev tawg ntawm nthwv dej hauv cov txheej txheem ntawm diffraction los ntawm ib lub siv lead ua. Nws feem ntau yog siv los txhuam qhov chaw los yog kom tau txais kev ntsuas ntawm qhov chaw. Yog li ntawd, cov txheej txheem no yog siv los ntsuas crystal orientation. Ib tug Laue diffraction qauv yog muab los ntawm pawg ntawm parallel atomic txheej nyob rau hauv ib tug siv lead ua; tus qauv yog ib txwm array ntawm me ntsis ntawm cov duab emulsion.
Daim duab 2: Laue Pattern muab los ntawm Crystal
Kev ntsuas yog tsim los ntawm kev sib kis lossis rov qab rov qab ntawm X-ray kab teeb. Thaum ib qho piv txwv uas muaj ib hom crystals yog siv rau qhov kev xeem, siab mob siab rau diffraction yuav tau. Lub symmetry ntawm Laue qauv yog feem ntau siv rau daim ntaub ntawv. Yog hais tias lub X ray beam nkag mus rau qhov sib npaug mus rau qhov siab-symmetry ntawm cov lattice, ces tus qauv Laue muab los ntawm cov nqaj ntawd kuj yog cov qauv siab. Piv txwv li, yog hais tias cov kab hluav taws xob nkag mus rau qhov sib npaug mus rau ntawm ntug ntawm chav tsev ntawm cov siv lead ua, cov nqaj no muab plaub-fold symmetrical qauv ntawm Laue me ntsis.
Qhov txawv ntawm Bragg thiab Laue Diffraction yog dab tsi?
Bragg vs Laue Diffraction |
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| Bragg diffraction muab cov ces kaum rau coherent thiab incoherent scattering los ntawm ib tug siv lead ua lattice. | Laue diffraction cuam tshuam nrog kev tawg ntawm nthwv dej hauv cov txheej txheem ntawm diffraction los ntawm crystal. |
| Principal | |
| Bragg diffraction xav tau lattices uas tau muab faib ua cov tsev neeg sib txawv ntawm cov dav hlau. | Laue diffraction tsis xav tau cov dav hlau tshwj xeeb lossis sib nrug. |
| Reflection | |
| Bragg diffraction xav tau kev xav txog qhov xwm txheej hluav taws xob. | Lau diffraction tsis xav kom cov hluav taws xob ua kom pom tseeb. |
Summary – Bragg vs Laue Diffraction
Bragg thiab Laue diffractions yog siv los ua cov txheej txheem crystallographic thiab cov cai los piav txog cov tshuab siv lead ua sib txawv. Qhov sib txawv tseem ceeb ntawm Bragg thiab Laue diffraction yog Bragg diffraction muab cov ces kaum rau coherent thiab incoherent scattering los ntawm ib tug siv lead ua lattice whereas Laue diffraction hais txog qhov tawg ntawm nthwv dej nyob rau hauv tus txheej txheem ntawm diffraction los ntawm ib tug crystal.
