《固体化学》课程教学课件（英文讲稿）Chapter 3 X-ray

s3X-raydiffractionMotivation:.X-ray diffraction is used to obtain structurainformation about crystalline solids· Useful in biochemistry to solve the 3Dstructures of complex biomolecules·Bridge the gaps between physics, chemistryand biology.X-ray diffraction is important for: Solid-state physics·Biophysics·Medical physics·Chemistry and Biochemistry

Motivation: •X-ray diffraction is used to obtain structural information about crystalline solids. •Useful in biochemistry to solve the 3D structures of complex biomolecules. •Bridge the gaps between physics, chemistry, and biology. X-ray diffraction is important for: • Solid-state physics • Biophysics • Medical physics • Chemistry and Biochemistry §3 X-ray diffraction

History of X-Ray Diffraction1895X-rays discovered byRoentgen1914First diffraction pattern of acrystal made by Knipping andvon Laue1915Theory to determine crystalstructure from diffractionpattern developed by Bragg1953DNA structure solved byWatson and CrickNowDiffraction improved bycomputer technology; methodsusedto determine atomicstructures and in medicalapplicationsThe first X-ray

History of X-Ray Diffraction 1895 X-rays discovered by Roentgen 1914 First diffraction pattern of a crystal made by Knipping and von Laue 1915 Theory to determine crystal structure from diffraction pattern developed by Bragg. 1953 DNA structure solved by Watson and Crick Now Diffraction improved by computer technology; methods used to determine atomic structures and in medical applications The first X-ray

HowDiffraction WorksWave lnteracting with a Single ParticleIncident beams scattered uniformly inall directionsWave Interacting with a SolidCrystalline MaterialRegular pattern of crystalline atomsproduces regular diffraction pattern.Diffraction pattern gives information oncrystalstructureNacl

How Diffraction Works  Wave Interacting with a Single Particle Incident beams scattered uniformly in all directions  Wave Interacting with a Solid  Crystalline Material Regular pattern of crystalline atoms produces regular diffraction pattern. Diffraction pattern gives information on crystal structure NaCl

How Diffraction Works: SchematicX-Ray DiffractionX-rayTubeHighVoltageCrystalX-rayOBeamLead ScreenPhotographicPlate

How Diffraction Works: Schematic NaCl

How Diffraction Works: SchematicX-RayDiffractionX-rayTubeHighVoltageCrystalX-rayOBeamLeadScreenPhotographicPlate

NaCl How Diffraction Works: Schematic

How Diffraction Works: Bragg's LawX-rays ofwavelengthlQQQSimilar principleto multiple slit experiments Constructive and destructive interference patternsdepend on lattice spacing and wavelength of radiationBy varying wavelength and observing diffractionpatterns, information about lattice spacing is obtained

nl=2dsin(Q) • Similar principle to multiple slit experiments • Constructive and destructive interference patterns depend on lattice spacing and wavelength of radiation • By varying wavelength and observing diffraction patterns, information about lattice spacing is obtained How Diffraction Works: Bragg’s Law d Q Q Q X-rays of wavelength l l

DestructiveConstructiveInterferenceInterferenceED(hkl)(hkl)(hkl)

X-ray sourceX-ray detectorIncidentX-raysReflectedX-raysA0ed-BDCdsinedsineDifference inpath length =BC+ CDBC = CD = dhk/SinOnkDifference in path length = 2dnkisinonklMustbeanintegral numberofWavelengths, n = 2dhk/sinehkl(n = 1, 2, 3, ...)入 = 2dhkisineBragg Equation

x-raydetectormonochromator20-Hcrystal(being rotatedinto diffr. conditions)x-raysfrom generator

(111)1002=0.1542 nm (CuK-radiation)80(see)60(200)40(311)(220)20(222)(331) (420)(400)0502030406070809010011012020 (degrees)