衍射花样指数化 苏五长 有一太
苏 玉 长 衍射花样指数化
The first step in analysing unknown powder pattern is often an attempt to find a unit cell that explains all observed lines in the spectrum You do not need additional crystallographic data, although if it exists it makes for faster and more reliable results The material to be analysed must be single phased and the experimental material must be very accurate 苏五长 有一太
苏 玉 长 The first step in analysing unknown powder pattern is often an attempt to find a unit cell that explains all observed lines in the spectrum. You do not need additional crystallographic data, although if it exists it makes for faster and more reliable results. The material to be analysed must be single phased and the experimental material must be very accurate
Indexing programs use only the positional information of the pattern and try to find a set of lattice constants(a, b,c, a, B,y)and individual Miller indices (hkl) for each line The form of equations to solve is complicated for the general case(triclinic)in direct space but is straightforward in reciprocal space. In the latter the set of equations is 苏五长 有一太
苏 玉 长 Indexing programs use only the positional information of the pattern and try to find a set of lattice constants (a,b,c,a,b,g) and individual Miller indices (hkl) for each line. The form of equations to solve is complicated for the general case (triclinic) in direct space but is straightforward in reciprocal space. In the latter the set of equations is：
Q=hA+kB+1 C+ hkD+ hIE kIF where the Q-values are easily derived from the diffraction angle (. This set has to be solved for the unknowns.ABC.de f which are in a simple way related to the lattice constants. Finding the proper values for the lattice parameters so that every observed d-spacing satifies a particular combination of Miller indices is the goal of indexing. It is not easy even for the cubic system but it is very difficult for the triclinic system 苏五长 有一太
苏 玉 长 Q = h2A + k2B + l2C+ hkD + hlE + klF where the Q-values are easily derived from the diffraction angle Q. This set has to be solved for the unknowns, A, B, C, D, E, F, which are in a simple way related to the lattice constants. Finding the proper values for the lattice parameters so that every observed d-spacing satifies a particular combination of Miller indices is the goal of indexing. It is not easy even for the cubic system, but it is very difficult for the triclinic system
There are two general approaches to indexing, the exhaustive and the analytical approach. Both of these approaches require very accurate d-spacing data. The smaller the errors the easier it is to test solutions because there are often missing data points due to intensity extinctions related to the symmetry or the structural arrangement or due to lack of resolution of the d-spacing themselves The earliest approaches were of the exhaustive type and were done by graphical fitting or numerical table fitting 苏五长 有一太
苏 玉 长 • There are two general approaches to indexing, the exhaustive and the analytical approach. Both of these approaches require very accurate d-spacing data. The smaller the errors, the easier it is to test solutions because there are often missing data points due to intensity extinctions related to the symmetry or the structural arrangement or due to lack of resolution of the d-spacing themselves. The earliest approaches were of the exhaustive type and were done by graphical fitting or numerical table fitting