[ Identification | Description | Input parameters | Output parameters | Links ]

The Bragg_crystal Component

* * Perfect, reflecting crystal with common cubic structures (diamond, fcc, or bcc, and others if symmetry form factor multipliers provided explicitly) * *

Identification

Description

* Bragg_crystal.comp supercedes Perfect_Crystal.comp with major edits and corrections.
*
* For details see:
* The optics of focusing bent-crystal monochromators on X-ray powder diffractometers with application to lattice parameter determination and microstructure analysis,
* Marcus H. Mendenhall,* David Black and James P. Cline, J. Appl. Cryst. (2019). 52, https://doi.org/10.1107/S1600576719010951
*
* Reads atomic formfactors from a data input file.
*
* The crystal code reflects ray in an ideal geometry, i.e. does not include surface imperfections or mosaicity.
* The crystal planes from which the reflection is made lies in the X-Z plane on the unbent crystal rotated
* by an angle alpha about the Y axis with respect to the crystal surface.
*
* The crystal itself is set in the X-Z plane positioned such that the long axis of the crystal surface coincides with
* the Z-axis, with its normam pointing in the positve Y-direction. The angle between the Bragg planes and the crystal surface is alpha
*
* This code has been validated against both experimental data
* (2 channel-cut 3-bounce Si 440 crystals together in non-dispersive mode, at Cu kalpha)
* and against theoretical rocking rocking curves from XOP for Si220 at Sc kalpha and Si440 at Cu kalpha.
*
* Changelog:
* - Off-axis rays fixed June 2015 so axial divergence corrections are right
* - Inclusion of polarization and temperature dependence (via Debye-Waller factor), June-September 2015
* - Errors in complex arithmetic in DarwinReflectivity2 corrected, September 2015, MHM
* - Symmetries for form factors corrected 20150924
* - Rotation code updated to use exact DarwinReflectivity Theta0, Thetah so answer is right even if alpha != 0. 20151009 MHM
* - Results for (1,1,1) etc. with complex form factor made to agree with XOP. December 1st, 2016
*
* Notation follows Tadashi Matsushita and Hiro-O Hashizume, X-RAY MONOCHROMATORS. Handbook on Synchrotron Radiation,North-Holland Publishing Company, 1:263–274, 1983.
*
* Non-copyright notice:
* Contributed by the National Institute of Standards and Technology; not subject to copyright in the United States.
* This is not an official contribution, in that the results are in no way certified by NIST.
*
*

Input parameters

Parameters in boldface are required; the others are optional.
NameUnitDescriptionDefault
length0.05
width0.02
V160.1826
form_factors"FormFactors.txt"
material"Si.txt"
alpha0.0
R00
debye_waller_B0.4632
crystal_type1
h1
k1
l1
structure_factor_scale_r0.0
structure_factor_scale_i0.0

Output parameters

Parameters in boldface are required; the others are optional.
NameUnitDescriptionDefault
prms

Links


[ Identification | Description | Input parameters | Output parameters | Links ]

Generated on 2021-08-13 08:57:53