Instrumental Peak Profile A large crystallite size,defect-free powder specimen will still produce diffraction peaks with a finite width The peak widths from the instrument peak profile are a convolution of: X-ray Source Profile ('n'e)Au!suejul Wavelength widths of Ka and Ko2 lines Size of the X-ray source Superposition of Ka and Ka2 peaks Goniometer Optics 47.047.247.447.647.8 Divergence and Receiving Slit widths 2θ(deg.) ·Imperfect focusing Patterns collected from the same sample with different instruments ·Beam size and configurations at MIT Penetration into the sampleInstrumental Peak Profile • A large crystallite size, defect-free powder specimen will still produce diffraction peaks with a finite width • The peak widths from the instrument peak profile are a convolution of: – X-ray Source Profile • Wavelength widths of K 1 and K  2 lines • Size of the X-ray source • Superposition of K 1 and K  2 peaks – Goniometer Optics • Divergence and Receiving Slit widths • Imperfect focusing • Beam size • Penetration into the sample 47.0 47.2 47.4 47.6 47.8 2  (deg.) Intensity (a.u.) Patterns collected from the same sample with different instruments and configurations at MIT