A component to simulate inelastic scattering in the incoherent approximation Takes into account one, two, and three phonon scattering explicitly, and multi-phonon scattering (with n>4) via the saddle point method
Author: Victor Laliena
Origin: University of Zaragoza
Date: 06.11.2018
Part of the Union components, a set of components that work together and thus expects geometry and physics within McStas. The use of this component requires other components to be used.
1) One specifies a number of processes using process components like this one 2) These are gathered into material definitions using Union_make_material 3) Geometries are placed using Union_box / Union_cylinder, assigned a material 4) A Union_master component placed after all of the above
Algorithm: Described elsewhere, see e.g. https://doi.org/10.3233/JNR-190117
Parameters in boldface are required; the others are optional.
|
Name |
Unit |
Description |
Default |
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|
T |
K |
Temperature |
394 |
|
density |
g/cm\(^{3}\) |
Material density |
6.0 |
|
M |
amu |
ion mass |
50.94 |
|
sigmaCoh |
barns |
Coherent scattering cross section |
0.0184 |
|
sigmaInc |
barns |
Incoherent scattering cross section |
5.08 |
|
DOSfn |
string |
Path to the file that contains the DoS |
NULL |
|
nphe_exact |
1 |
Number of terms in the phonon expansion taken exact. Has to be between 1 and 3. |
1 |
|
nphe_approx |
1 |
Number of terms in the phonon expansion taken approximate. |
0 |
|
approx |
1 |
Approximation type: 0 gaussian, 1 saddle point |
0 |
|
mph_resum |
0/1 |
Resumate the remaining terms of the phonon expansion via a saddle point: 0 No, 1 Yes |
0 |
|
nxs |
1 |
Number of energy points at which the total cross sections are precomputed |
1000 |
|
kabsmin |
A\(^{-1}\) |
Lower cut-off for the neutron wave-vector k |
0.1 |
|
kabsmax |
A\(^{-1}\) |
Higher cut-off for the neutron wave-vector k |
25 |
|
interact_fraction |
1 |
How large a part of the scattering events should use this process 0-1 (sum of all processes in material = 1) |
-1 |
|
init |
string |
Name of Union_init component (typically "init", default) |
"init" |
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Component source code found in file IncoherentPhonon_process.comp.