Rietveld analysis of powder neutron diffraction data displaying anisotropic crystallite size broadening

In order to accommodate anisotropic crystallite-size broadening effects in the Rietveld refinement of constant-wavelength powder neutron diffraction data, a modified function for the peak full width at half maximum has been evaluated for polycrystalline Ni(OD)₂. The function resulted in significantly better agreement between observed and calculated profiles (the weighted residual R_w.p decreased from 14.1 to 8.5%), and structural standard deviations were reduced by an average of 43%.