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McStas: Single_magnetic_crystal

[ Identification | Description | Input parameters | Links ]

The Single_magnetic_crystal Component

Mosaic magnetic single crystal with multiple scattering vectors.


  • Site:
  • Author: Erik B Knudsen and Linda Udby
  • Origin: DTU Physics
  • Date: Jan 2020


WARNING: This is an experimental component - no experimental validation has yet been done

Single magnetic crystal with mosaic. Delta-D/D option for finite-size effects.
Multiple scattering and secondary extinction included.
The mosaic may EITHER be specified isotropic by setting the mosaic input
parameter, OR anisotropic by setting the mosaic_h, mosaic_v, and mosaic_n

The scattering is computed solely in an spin up-down configuration. That is the
scattering is considered in relation to the externally defined vector (mx,my,mz), where it
can be either SF or NSF.
Simplifications and comments :
Lande splitting factor is assumed to be g=2
Magnetic form factors are set =1

Sample shape:
Sample shape may be a cylinder, a sphere, a box or any other shape
box/plate:       xwidth x yheight x zdepth
cylinder:        radius x yheight
sphere:          radius (yheight=0)
any shape:       geometry=OFF file

The complex geometry option handles any closed non-convex polyhedra.
It computes the intersection points of the neutron ray with the object
transparently, so that it can be used like a regular sample object.
It supports the OFF and NOFF file format but not COFF (colored faces).
Such files may be generated from XYZ data using qhull/powercrust, and
viewed with geomview
The default size of the object depends of the OFF file data, but its
bounding box may be resized using xwidth,yheight and zdepth.

Also, always use a non-zero value of delta_d_d.

Input parameters

Parameters in boldface are required; the others are optional.
atom_sitesFile name containing the atoms present in the unit cell. Use0
geometryName of an Object File Format (OFF) file for complex geometry.NULL
xwidthWidth of crystal [m]0
yheightHeight of crystal [m]0
zdepthDepth of crystal (no extinction simulated) [m]0
radiusOuter radius of sample in (x,z) plane [m]0
delta_d_dLattice spacing variance, gaussian RMS [1]1e-4
mosaicCrystal mosaic (isotropic), gaussian RMS [arc minutes]-1
mosaic_hHorizontal (rotation around Y) mosaic (anisotropic),-1
mosaic_vVertical (rotation around Z) mosaic (anisotropic),-1
mosaic_nOut-of-plane (Rotation around X) mosaic (anisotropic),-1
recip_cellChoice of direct/reciprocal (0/1) unit cell definition [1]0
q_min[AA^⁻1] lower boundary of momentum transfer range to generate hkls in0
q_max[AA^⁻1] upper boundary of momentum transfer range to generate hkls in-1
myCoordinates of vector defining the SF/NSF direction [1]1
nbUnit cell multipliers. The specified unit cell vectors are scaled by these factors. Note that the mulitpliers are applied directly to the raw input data. I.e. if recip. cell vectors are given, multipliers should be <1 (= 1/n). F.i. used to specify a magnetic unit cell which is larger than the chemical unit cell.1
ayCoordinates of first (direct/recip) unit cell vector [AA or AA^-1]0
byCoordinates of second (direct/recip) unit cell vector [AA or AA^-1]0
cyCoordinates of third (direct/recip) unit cell vector [AA or AA^-1]0
p_transmitMonte Carlo probability for neutrons to be transmitted-1
sigma_absabsorption cross-section per unit cell at 2200 m/s [barns]0
sigma_incincoherent scattering cross-section per unit cell [barns]0
orderlimit multiple scattering up to given order0


[ Identification | Description | Input parameters | Links ]

Generated on 2023-09-19 20:01:36

Last Modified: Tuesday, 16-Apr-2024 20:05:21 CEST
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