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A new method of determining lattice parameters by peak fitting of X-ray diffraction pattern, without involving structure parameters, is introduced. The method can be applied to a single phase and one phase in multi-phase diffraction patterns. It can avoid getting different fitting results caused by using different extrapolation functions, and can get a more accurate result in a short time. The application program of the method has been used in the practical work. For improving the fitting accuracy, the program can also adjust off-axis deviation of the sample surface and the goniometric mechanical zero.

This paper studies the effect of measuring angle error in X-ray powder diffractometer, which is caused by diffractometer inherent angle scale error resulting from mechanical manufacture, on the precision of calculated lattice parameter. It represents the theoretical limit of the consistency of the lattice parameters obtained by different diffractometers and laboratories. We use the calculated polysilicon diffraction patterns with random angle error to simulate the results measured by many sets of diffractometers of some manufacturing precision, then calculate and analyze the lattice parameters by three methods.