stephens_peakshape
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stephens_peakshape [2011/02/11 14:45] – johnsoevans | stephens_peakshape [2022/11/03 15:08] (current) – external edit 127.0.0.1 | ||
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+ | ====== Stephens_peakshape ====== | ||
+ | Description: | ||
+ | |||
+ | Contributed by: Peter Stephens, Robert Dinnebier, Andreas Leinweber | ||
+ | |||
+ | An alternative approach to spherical harmonics for hkl dependent peak shapes by | ||
+ | Peter Stephens (P.W. Stephens, J. Appl. Cryst. (1999) 32, 281-9) as coded in gsas. | ||
+ | eta term allows mixture of Gauss/ | ||
+ | |||
+ | Built in macros for different point groups are: | ||
+ | <code topas> | ||
+ | Stephens_triclinic (-1) | ||
+ | Stephens_monoclinic (2/m) | ||
+ | Stephens_orthorhombic (mmm) | ||
+ | Stephens_tetragonal_low (4/m) | ||
+ | Stephens_tetragonal_high (4/mmm) | ||
+ | Stephens_trigonal_low (-3) | ||
+ | Stephens_trigonal_high (-3m1) | ||
+ | Stephens_trigonal_high_2 (-31m) | ||
+ | Stephens_hexagonal (6/m and 6/mmm) | ||
+ | Stephens_cubic (m-3 and m-3m) | ||
+ | </ | ||
+ | |||
+ | Note that for all trigonal Laue classes the macros assume the hexagonal setting of the unit cell | ||
+ | |||
+ | As an example try the following in your input file (macros you need are below). | ||
+ | |||
+ | <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, | ||
+ | <code topas> | ||
+ | macro Stephens_tetragonal(s400, | ||
+ | { | ||
+ | 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/ | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | Stephens_monoclinic(s400, | ||
+ | |||
+ | <code topas> | ||
+ | macro Stephens_monoclinic(s400, | ||
+ | { | ||
+ | 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/ | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | Stephens_hexagonal(s400, | ||
+ | |||
+ | <code topas> | ||
+ | macro Stephens_hexagonal(s400, | ||
+ | { | ||
+ | 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/ | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | Stephens_orthorhombic(s400, | ||
+ | |||
+ | <code topas> | ||
+ | macro Stephens_orthorhombic(s400, | ||
+ | { | ||
+ | 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/ | ||
+ | } | ||
+ | </ |