[ Identification | Description | Input parameters | Output 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

• Author: Kim Lefmann
• Origin: Risoe
• Date: 04.02.04
• Version:(Unknown)

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	unphysical	[meV] Bandgap energy	0

Output parameters

Name	Unit	Description	Default
V_rho	AA^-3	Atomic density
V_my_s	m^-1	Attenuation factor due to incoherent scattering
V_my_a_v	m^-1	Attenuation factor due to absorbtion
DV
parms

Links

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

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[ Identification | Description | Input parameters | Output parameters | Links ]

Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Tue May 26 13:03:59 2020

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Last Modified: Tuesday, 26-May-2020 15:03:59 CEST