关键词: 粉晶, X射线, 指标化

Abstract: The X-ray diffraction values of powder crystal specimens of unknown crystal system of 2-nitro-4-methylphenylarsonic acid were indexed successfully by the improved trial-and-error method.This method is also suitable for indexing for powder diffraction values of hexagonal, tetragonal, or-thorhombic, monoclinic and triclinic substance.The lattice parameters obtained from the powder diffraction values were refined by the least-square method.Indexing of the powder diffraction data and refinement of the unit-cell parameters for 2-nitro-4-methylphenylarsonic acid are reported.The refined crystallographic data are:C₇H₈NO₅As, 10-C_2h¹-P_2/m(approximately).a= 10.466(8)Å, b = 8.389(2)Å, c=9.918(3)Å, β=95.08(3)°, Z=4, D_m=1.970, D_x= 1.999 g·cm^-3.The quantitative figure of merit(F_N) is F₂₀=27.

Key words: Powder crystal, X-ray, Indexing