[ Identification | Description | Input parameters | Links ]

The `Phonon_BvK_PG` Component

A sample for phonon scattering based on cross section expressions from the Boothroyd textbook based upon the algorithm from component Phonon_simple (with expressions from Squires, Ch. 3) Using the Born-von Karman force constnts and the normal mode formalism

Identification

Site:
Author: Kim Lefmann
Origin: NBI, KU
Date: 06.12.2025

Description

Single-cylinder or slap shaped shape.
Absorption included.
No multiple scattering.
No incoherent scattering emitted, but incoherent is present in attenuation
No attenuation from coherent scattering. No Bragg scattering.
Specialized for Pyrolytic Graphite (PG)

Algorithm:
0. Always perform the scattering if possible (otherwise ABSORB)
1. Choose direction within a focusing solid angle
2. Select a phonon mode at random (alternatively mode number fixed by user)
3. Calculate the zeros of (E_i-E_f-hbar omega(kappa)) as a function of k_f
4. Choose one value of k_f (there always at least one possible; see e.g. Squires)
5. Perform the correct weight transformation
For details: see article A. F. Davidsen et al, manuscript for J Neutron Res 2026

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
hh			0
kk			0
ll			0
radius	m	Outer radius of sample in (x,z) plane	0
xwidth	m	Horiz. dimension of sample if slap	0
yheight	m	Height of sample in y direction	0
zdepth	m	Depth of sample if slap	0
sigma_abs			0
sigma_inc			0
DW			1
T
focus_r			0
focus_xw			0
focus_yh			0
focus_aw			0
focus_ah			0
target_x			0
target_y			0
target_z			0
target_index			0
mode_input
e_steps_low
e_steps_high
verbose_input			0
dispersion			0

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

The Phonon_BvK_PG Component

Identification

Description

Input parameters

Links

The `Phonon_BvK_PG` Component