[ 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.

Name | Unit | Description | Default |
radius | m | Outer radius of sample in (x,z) plane |  |
yheight | m | Height of sample in y direction |  |
sigma_abs | barns | Absorption cross section at 2200 m/s per atom |  |
sigma_inc | barns | Incoherent scattering cross section per atom |  |
a | AA | fcc Lattice constant |  |
b | fm | Scattering length |  |
M | a.u. | Atomic mass |  |
c | meV/AA^(-1) | Velocity of sound |  |
DW | 1 | Debye-Waller factor |  |
T | K | Temperature |  |
target_x | m | position of target to focus at . Transverse coordinate | 0 |
target_y | m | position of target to focus at. Vertical coordinate | 0 |
target_z | m | position of target to focus at. Straight ahead. | 0 |
target_index | 1 | relative index of component to focus at, e.g. next is +1 | 0 |
focus_r | m | Radius of sphere containing target. | 0 |
focus_xw | m | horiz. dimension of a rectangular area | 0 |
focus_yh | m | vert. dimension of a rectangular area | 0 |
focus_aw | deg | horiz. angular dimension of a rectangular area | 0 |
focus_ah | deg | vert. angular dimension of a rectangular area | 0 |
gap | meV | Bandgap energy (unphysical) | 0 |

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

## Links

- Source code for `Phonon_simple.comp`.
- The test/example instrument Test_Phonon.instr.

[ Identification | Description | Input parameters | Links ]