电镜标定.pdf

电子衍射谱标定练习Indexing: the zone axis [uvw] (plane normal) and at least one low index spot (hkl) (normally two spots), with hu+kv+lw= Al3Ni of 2D patterns?3D reciprocal lattice?3D real lattice?orientation/phase identificationThe size of diffraction patterns(1/λ)/ghkl=L/Rhkl’R’d = λLWhen is θsmall (electron diffraction),Rd=λL=diffraction constantS0/λ= k0S/λ= kghkl(hkl)000(hkl)L=相机长度θRhkl’RhklIndexing a pattern of a known substanceA table of interplanar spacings d is needed. a) Choose three spots such as h3k3l3, h1k1l1, ) Measure the d values, and thus determine the ) By trial and error a consistent set of indices is chosen such that h3k3l3= h1k1l1+ ) [uvw], the zone axis, is obtained by any two vectors (. R1×R2)S0/λ= k0S/λ= kghkl(hkl)000相机长度Rhklh1k1l1h2k2l2h3k3l3[uvw]R1R2Indexing a pattern of a known substanceExample: an fcc crystal with a = . d=a/(h2 +k2 +l2)1/2. A diffraction pattern is shown below with R1=R2=, R1^R2=. Lλ= . a) Choose three spots R1, R2, R3(R3=R1+ R2)b) d1= d2= Lλ/R1= , ?{111}.c) A consistent set of indices is 002= 111 + ) R1×R2=[110], the zone [110]R3a) 直接利用已知d值标定已知物质的d值计算1、使用公式:立方系d=a/(h2 +k2 +l2)1/22、使用软件:Carine3、查XRD标准粉末卡Standard powder XRD data; b) 查表标定法利用软件计算出某种物质所有可能的衍射谱(R1+ R2=R3)