結(jié)晶學(xué)chap5crystaldiffraction-展示頁(yè)
2024-12-17 11:43本頁(yè)面
【正文】 ?????hn n n nh a k b lcr x a y b z c? ? ? ?? ? ?? ? ?Electric field at rn : Electric field at P (defection)： E0 : electric field amplitude of the incident beam at rn c???nnnnh lzkyhxr ???? ???hnn rSSrRXX ?????????? )( 021Fh 44 ife?33 ife?22 ife?11 ife?If centrosymmetric and no anomalous scatter: Bh=0。α=tan A39。 = = tan αA 39。The Bragg approach to diffraction is to regard crystals as built up in layers or planes such that each act as a semitransparent mirror. The derivation of Bragg‘s Equation is shown in the following figure. Crystal Diffraction Bragg‘s Equation 2d sin? = n? d l ? ? Bragg Diffraction Structure Factor Calculation 90? 180? 270? 360? 450? 540? 90? 180? 270? 450? 540? 90? 180? 270? 360? 450? 540? 0 0 0 X1 ? f1cos? X2 ? f2cos? Xtotal ? (f1?f2)cos? ? ? ? X1 X2 Xtotal f1 f2 P1 P2 f1 f2 ? ? Resultant 90? 180? 450? 90? 180? 270? 450? 90? 180? 360? 450? 0 0 0 ? ? ? X1 X2 Xtotal 540? 540? 540? 360? X1 ? f1cos(???1) X2 ? f2cos(???2) f1 f2 ?F ? f1 P1 ? f2 ? P2 ?1 ?2 Resultant Combination of Wave Direction (h, k, l) Amplitude ?F?hkl Phase ? Xtotal ? f1cos(???1) ? f2cos(???2) ? cos? (f1cos?1 ? f2cos?2) ? sin? (f1sin?1 ? f2sin?2
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