The `Single_magnetic_crystal` Component

Mosaic magnetic single crystal with multiple scattering vectors.

Identification

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

Description

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
parameters.

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.

Name	Unit	Description	Default
atom_sites		File name containing the atoms present in the unit cell. Use	0
geometry		Name of an Object File Format (OFF) file for complex geometry.	NULL
xwidth		Width of crystal [m]	0
yheight		Height of crystal [m]	0
zdepth		Depth of crystal (no extinction simulated) [m]	0
radius		Outer radius of sample in (x,z) plane [m]	0
delta_d_d		Lattice spacing variance, gaussian RMS [1]	1e-4
mosaic		Crystal mosaic (isotropic), gaussian RMS [arc minutes]	-1
mosaic_h		Horizontal (rotation around Y) mosaic (anisotropic),	-1
mosaic_v		Vertical (rotation around Z) mosaic (anisotropic),	-1
mosaic_n		Out-of-plane (Rotation around X) mosaic (anisotropic),	-1
recip_cell		Choice of direct/reciprocal (0/1) unit cell definition [1]	0
q_min		[AA^⁻1] lower boundary of momentum transfer range to generate hkls in	0
q_max		[AA^⁻1] upper boundary of momentum transfer range to generate hkls in	-1
mx			0
my			1
mz			0
na			1
nb		Unit cell multipliers. The specified unit cell vectors are scaled by these factors.	1
nc			1
ax			0
ay		Coordinates of first (direct/recip) unit cell vector [AA or AA^-1]	0
az			0
bx			0
by		Coordinates of second (direct/recip) unit cell vector [AA or AA^-1]	0
bz			0
cx			0
cy		Coordinates of third (direct/recip) unit cell vector [AA or AA^-1]	0
cz			0
p_transmit		Monte Carlo probability for neutrons to be transmitted	-1
sigma_abs		absorption cross-section per unit cell at 2200 m/s [barns]	0
sigma_inc		incoherent scattering cross-section per unit cell [barns]	0
order		limit multiple scattering up to given order	0

AT (	,	,		) RELATIVE
ROTATED (	,	,		) RELATIVE

The Single_magnetic_crystal Component

Identification

Description

Input parameters

Links

The `Single_magnetic_crystal` Component