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McStas: Phonon_simple

[ Identification | Description | Input parameters | Links ]

The Phonon_simple Component

A sample for phonon scattering based on cross section expressions from Squires, Ch.3. Possibility for adding an (unphysical) bandgap.

Identification

  • Site:
  • Author: Kim Lefmann
  • Origin: Risoe
  • Date: 04.02.04

Description

Single-cylinder shape.
Absorption included.
No multiple scattering.
No incoherent scattering emitted.
No attenuation from coherent scattering. No Bragg scattering.
fcc crystal n.n. interactions only
One phonon branch only -> phonon polarization not accounted for.
Bravais lattice only. (i.e. just one atom per unit cell)

Algorithm:
0. Always perform the scattering if possible (otherwise ABSORB)
1. Choose direction within a focusing solid angle
2. Calculate the zeros of (E_i-E_f-hbar omega(kappa)) as a function of k_f
3. Choose one value of k_f (always at least one is possible!)
4. Perform the correct weight transformation

Input parameters

Parameters in boldface are required; the others are optional.
NameUnitDescriptionDefault
radiusmOuter radius of sample in (x,z) plane
yheightmHeight of sample in y direction
sigma_absbarnsAbsorption cross section at 2200 m/s per atom
sigma_incbarnsIncoherent scattering cross section per atom
aAAfcc Lattice constant
bfmScattering length
Ma.u.Atomic mass
cmeV/AA^(-1)Velocity of sound
DW1Debye-Waller factor
TKTemperature
target_xmposition of target to focus at . Transverse coordinate0
target_ymposition of target to focus at. Vertical coordinate0
target_zmposition of target to focus at. Straight ahead.0
target_index1relative index of component to focus at, e.g. next is +10
focus_rmRadius of sphere containing target.0
focus_xwmhoriz. dimension of a rectangular area0
focus_yhmvert. dimension of a rectangular area0
focus_awdeghoriz. angular dimension of a rectangular area0
focus_ahdegvert. angular dimension of a rectangular area0
gapmeVBandgap energy (unphysical)0
AT ( , , ) RELATIVE
ROTATED ( , , ) RELATIVE

Links


[ Identification | Description | Input parameters | Links ]

Generated on 2024-01-03 11:47:43


Last Modified: Wednesday, 03-Jan-2024 19:59:11 CET
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