hkl_dependent_peak_shapes
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hkl_dependent_peak_shapes [2009/08/27 16:55] – created johnsoevans | hkl_dependent_peak_shapes [2022/11/03 15:08] (current) – external edit 127.0.0.1 | ||
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+ | ====== hkl-dependent Peak Shapes ====== | ||
+ | |||
+ | There are lots of ways of doing this. | ||
+ | |||
+ | One excellent approach (sometimes with fewer parameters than a spherical harmonic function) is to use the Stephens approach (P.W. Stephens, J. Appl. Cryst. (1999) 32, 281-9) as coded in gsas. Peter, Robert Dinnebier and Andreas Leineweber have worked out the macros for this. eta term allows mixture of Gauss/ | ||
+ | |||
+ | <code topas> | ||
+ | prm s004 153.55044` | ||
+ | prm s220 28029.32854` | ||
+ | prm s202 -1067.03124` | ||
+ | ........ | ||
+ | prm eta 0.52180` min 0 max 1 | ||
+ | Stephens_tetragonal(s400, | ||
+ | </ | ||
+ | |||
+ | The macros you'll need are below. | ||
+ | |||
+ | <code topas> | ||
+ | { | ||
+ | prm mhkl = Abs(S400 (H^4+ K^4)+ S004 L^4+ S220 H^2 K^2 + S202 (H^2 L^2 + K^2 L^2) ); | ||
+ | |||
+ | prm pp = D_spacing^2 * Sqrt(Max(mhkl, | ||
+ | gauss_fwhm = 1.8/ | ||
+ | lor_fwhm = 1.8/ | ||
+ | }</ | ||
+ | |||
+ | <code topas> | ||
+ | { | ||
+ | prm mhkl = H^4 s400 + K^4 s040 + L^4 s004 + | ||
+ | H^2 K^2 s220 + H^2 L^2 s202 + K^2 L^2 s022 + | ||
+ | H K^2 L s121 + | ||
+ | H L^3 s103 + H^3 L s301; | ||
+ | |||
+ | prm pp = D_spacing^2 * Sqrt(Max(mhkl, | ||
+ | |||
+ | gauss_fwhm = 1.8/ | ||
+ | lor_fwhm = 1.8/ | ||
+ | }</ | ||
+ | |||
+ | <code topas> | ||
+ | { | ||
+ | prm mhkl = H^4 s400 + K^4 s400 + L^4 s004 + | ||
+ | H^2 K^2 3 s400 + H^2 L^2 s202 + K^2 L^2 s202 + | ||
+ | H K L^2 s202 + | ||
+ | H^3 K 2 s400 + H K^3 2 s400; | ||
+ | |||
+ | prm pp = D_spacing^2 * Sqrt(Max(mhkl, | ||
+ | |||
+ | gauss_fwhm = 1.8/ | ||
+ | lor_fwhm = 1.8/ | ||
+ | }</ | ||
+ | |||
+ | <code topas> | ||
+ | { | ||
+ | prm mhkl = H^4 s400 + K^4 s040 + L^4 s004 + | ||
+ | H^2 K^2 s220 + H^2 L^2 s202 + K^2 L^2 s022; | ||
+ | |||
+ | prm pp = D_spacing^2 * Sqrt(Max(mhkl, | ||
+ | |||
+ | gauss_fwhm = 1.8/ | ||
+ | lor_fwhm = 1.8/ | ||
+ | } | ||
+ | </ | ||
+ |