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

The Filter_powder Component

Incorporating code from Single_crystal, written by KN, December 1999 Box-shaped powder filter or sample (BUGGY)

Identification

Description

This is a general box-shaped powder filter/sample which simulates
multiple coherent scattering vectors and absorption (incoherent
scattering is modelled as absorption).
Crystal structure is specified with an ascii data file. Each line
contains seven numbers, separated by white space. The first three numbers
are the (h,k,l) indices of the reciprocal lattice point, and the last
number is the value of the structure factor |F|**2, in barns.  (The rest
of the numbers are not used; the file is in the format output by the
Crystallographica program).
Optionally, a number of absorbing blades may be incorporated into the
filter - these are X-Z or Y-Z planes evenly spaced along the X or Y axis
of the filter which absorb any neutron encountering them.

EXAMPLE:
You may use, as a filter, something like (5x5x5 cm cube):
    Filter_powder(
     ax=2.714, by=2.714, cz=4.405, cc=120,
     sigma_a = 0.0156,
     reflections="BeO.lau")

and as a sample (1x1x1 cm cube):
    Filter_powder(
     ax=3.8186, by=3.8186, cz=11.6777,
     xmin =-0.005 , xmax = 0.005, ymin = -0.005, ymax = 0.005,
     zmin = -0.005, zmax = 0.005, XBlades=0, YBlades=0,
     sigma_a = 0, reflections="YBaCuO.lau")                                  *
%BUGS

This component is known to produce wrong results but is given in hope
somebody will find it useful and fix it.

WARNING: This is a contributed Component.

Input parameters

Parameters in boldface are required; the others are optional.
Name Unit Description Default
reflections string File name containing structure factors of reflections  
xmin m Lower x-value of powder sample -0.05
xmax m Upper x-value of powder sample 0.05
ymin m Lower y-value of powder sample -0.05
ymax m Upper y-value of powder sample 0.05
zmin m Lower z-value of powder sample -0.05
zmax m Upper z-value of powder sample 0.05
ax AA ,ay,az : Coordinates of first unit cell vector 2.714
ay 0
az 0
bx AA ,by,bz : Coordinates of second unit cell vector 0
by 2.714
bz 0
cx AA ,cy,cz : Coordinates of third unit cell vector 0
cy 0
cz 4.405
pack 1 Packing factor of powder 1
sigma_a barns Absorption cross-section per unit cell at 2200 m/s 0.0156
DW 1 Debye-Waller factor of reflection 1
XBlades 1 Number of vertical absorbing blades 2
YBlades 1 Number of horizontal absorbing blades 2
aa - ,bb,cc : unit cell angles alpha, beta and gamma (deg). Then uses norms of vectors a,b and c as lattice parameters. 90
bb 90
cc 0

Output parameters

Name Unit Description Default
XBlade_pos  
YBlade_pos  
xb  
xt  
yb  
yt  
pf_hkl_info  

Links


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

Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Fri Apr 24 19:09:21 2009