[ Identification | Description | Input parameters | Links ]

The Single_crystal_inelastic Component

An extension of Single crystal with material dispersion



The component handles a 4D S(q,w) material dispersion, and scatters neutrons
out of it. It is based on the Isotropic_Sqw methodology, extended to 4D.

A number of approximations are applied:

- geometry is restricted to box, cylinder and sphere
- ignore absorption, multiple scattering and incoherent scattering
- no temperature handling. The temperature must be taken into account when
generating the S(q,w) data sets, which should contain Bose/detailed balance.
- intensity is used as provided by the S(q,w) data set

We recommend that you first try the Test_Single_crystal_inelastic example to
learn how to use this complex component.

4D S(q,w) data files

The input data file derives from other McStas formats. It may contain structural
information as in Lau/Laz files, and a list of S(q,w) [one per row] with 5 columns

[ H K L E S(q,w) ]

An example file example.sqw4 is provided in the McStas/Data directory.

You may generate such files using iFit  such as:

s = sqw_vaks('defaults');             % a 4D model
d = iData(s);                         % use default coarse grid for axes [-0.5:0.5]
saveas(d, 'sx_coh.sqw4', 'mcstas');   % export to 4D Sqw file

This component is undergoing validation.

Input parameters

Parameters in boldface are required; the others are optional.
mosaic_ABarcmin,arcmin,1,1,1,1,1,1In Plane mosaic rotation and plane vectors (anisotropic),{0,0, 0,0,0, 0,0,0}
sqwstringName of a 4d S(q,w) file - example.sqw4 is included in your installation0
geometrystringName of an Object File Format (OFF) or PLY file for complex geometry. The OFF/PLY file may be generated from XYZ coordinates using qhull/powercrust.0
xwidthmWidth of crystal.0
yheightmHeight of crystal.0
zdepthmDepth of crystal (no extinction simulated)0
radiusmOuter radius of sample in (x,z) plane.0
delta_d_d1Lattice spacing variance, gaussian RMS.1e-4
mosaicarcminIsotropic crystal mosaic, gaussian RMS. Puts the crystal in the isotropic mosaic model state, thus disregarding other mosaicity parameters.-1
mosaic_aarcminHorizontal (rotation around lattice vector a) mosaic (anisotropic), gaussian RMS. Put the crystal in the anisotropic crystal vector state. I.e. model mosaicity through rotation around the crystal lattice vectors. Has precedence over in-plane mosaic model.-1
mosaic_barcminVertical (rotation around lattice vector b) mosaic (anisotropic), gaussian RMS.-1
mosaic_carcminOut-of-plane (Rotation around lattice vector c) mosaic (anisotropic), gaussian RMS.-1
recip_cell1Choice of direct/reciprocal (0/1) unit cell definition.0
barns1Flag to indicate if |F|^2 from 'reflections' is in barns or fm^2.0
axAA / AA^-1Coordinates of first (direct/recip) unit cell vector.0
ayAA / AA^-1a on y axis0
azAA / AA^-1a on z axis0
bxAA / AA^-1Coordinates of second (direct/recip) unit cell vector.0
byAA / AA^-1b on y axis0
bzAA / AA^-1b on z axis0
cxAA / AA^-1Coordinates of third (direct/recip) unit cell vector.0
cyAA / AA^-1c on y axis0
czAA / AA^-1c on z axis0
p_transmit1Monte Carlo probability for neutrons to be transmitted-1
sigma_absbarnsAbsorption cross-section per unit cell at 2200 m/s.0
sigma_incbarnsIncoherent scattering cross-section per unit cell.0
aadegUnit cell angles alpha, beta and gamma. Then uses norms of0
bbdegBeta angle.0
ccdegGamma angle.0
order1Limit multiple scattering up to given order0
RXmRadius of horizontal along X lattice curvature. flat for 0.0
RYmRadius of vertical lattice curvature. flat for 0.0
RZmRadius of horizontal along Z lattice curvature. flat for 0.0


[ Identification | Description | Input parameters | Links ]

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