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

The PowderN Component

General powder sample (N lines, single scattering, incoherent scattering)

Identification

Description

General powder sample with
        many scattering vectors
        possibility for intrinsic line broadening
        incoherent backgorund ratio is specified by user.
        No multiple scattering. No secondary extinction.

Based on Powder1/Powder2/Single_crystal.
Geometry is a powder filled cylinder or a box.
Incoherent scattering is only provided here to account for a background
The efficient is highly improved when restricting the vertical scattering
range on the Debye-Scherrer cone (with 'd_phi').
The unit cell volume Vc may also be computed when giving the density,
the atomic/molecular weight and the number of atoms per unit cell.

Example: PowderN(reflections = "c60.lau", d_phi = 15 , radius = 0.01,
  yheight = 0.05, Vc = 1076.89, sigma_abs = 0, Delta_d=0, DW=1,
  format=Crystallographica)

Powder definition and file format

Powder structure is specified with an ascii data file 'reflections'.
The powder data are free-text column based files.
Lines begining by '#' are read as comments (ignored) but they may contain
the following keywords (in the header):
  #Vc 
  #sigma_abs 
  #sigma_inc 
  #Debye_Waller 
  #Delta_d/d 
These values are not read if entered as component parameters (Vc=...)

The signification of the columns in the numerical block may be
set using the 'format' parameter. Built-in formats are:
  format=Crystallographica
  format=Fullprof
  format=Lazy
and these specifications it is important NOT to use quotes, as shown.

An other possibility to define other formats is to set directly
the signification of the columns as a vector of indexes in the order
  format={j,d,F2,DW,Delta_d/d,1/2d,q,F}
Signification of the symbols is given below. Indexes start at 1.
Indexes with zero means that the column is not present, so that:
  Crystallographica={ 4,5,7,0,0,0,0,0 }
  Fullprof         ={ 4,0,8,0,0,5,0,0 }
  Lazy             ={17,6,0,0,0,0,0,13}
Here again, NO quotes should be around the 'format' value.

At last, the format may be overridden by direct definition of the
column indexes in the file itself by using the following keywords
in the header (e.g. '#column_j 4'):
  #column_j 
  #column_d 
  #column_F2 
  #column_F  
  #column_DW 
  #column_Dd 
  #column_inv2d 
  #column_q 

Input parameters

Parameters in boldface are required; the others are optional.
Name Unit Description Default
reflections string Input file for reflections. Use only incoherent scattering if NULL or ""  
format no quotes name of the format, or list of column indexes (see Description). Undefined
d_phi deg,0-180 Angle corresponding to the vertical angular range to focus to, e.g. detector height. 0 for no focusing 0
radius m Radius of sample in (x,z) plane 0.01
yheight m Height of sample y direction 0.05
pack 1 Packing factor 1
Vc AA^3 Volume of unit cell=nb atoms per cell/density of atoms 0
sigma_abs fm^2 Absorption cross section per unit cell at 2200 m/s 0
sigma_inc fm^2 Incoherent cross section per unit cell 0
Delta_d Angs global relative Delta_d/d spreading when the 'w' column is not available. Use 0 if ideal. 0
frac 1 Fraction of incoherently scattered neutron rays 0
xwidth m horiz. dimension of sample, as a width 0
zthick m thickness of sample 0
h m the same as yheight 0
DW 1 global Debey-Waller factor when the 'DW' column is not available. Use 1 if included in F2 0
nb_atoms 1 number of atoms per unit cell 1
density g/cm^3 density of material. V_rho=density/weight/1e24*N_A. 0
weight g/mol atomic/molecular weight of material 0

Output parameters

Name Unit Description Default
line_info  
Nq  
my_s_v2  
my_s_v2_sum  
my_a_v  
my_inc  
q_v  
w_v  
isrect  
columns  

Links


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

Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Fri Oct 27 12:32:23 2006