[ Identification | Description | Input parameters | Output parameters | Links ]
PowderN
ComponentGeneral 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 Concentricity PowderN assumes 'concentric' shape, i.e. can contain other components inside its optional inner hollow. Example, Sample in Al cryostat: COMPONENT Cryo = PowderN(reflections="Al.laz", radius = 0.01, radius_i = 0.009, concentric = 1) AT (0,0,0) RELATIVE Somewhere COMPONENT Sample = some_other_component(with geometry FULLY enclosed in the hollow) AT (0,0,0) RELATIVE Somewhere COMPONENT Cryo2 = COPY(Cryo)(concentric = 0) AT (0,0,0) RELATIVE Somewhere (The second instance of the cryostat component can also be written out completely using PowderN(...). In both cases, this second instance needs concentric = 0.)
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 | Outer radius of sample in (x,z) plane | 0 |
radius_i | m | Radius of optional inner hollow | 0 |
yheight | m | Height of sample y direction | 0 |
pack | 1 | Packing factor | 1 |
Vc | AA^3 | Volume of unit cell=nb atoms per cell/density of atoms | 0 |
sigma_abs | barns | Absorption cross section per unit cell at 2200 m/s | 0 |
sigma_inc | barns | 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 | 0.1 |
tfrac | 1 | Fraction of transmitted (only attenuated) neutron rays | 0.1 |
xwidth | m | horiz. dimension of sample, as a width | 0 |
zthick | m | thickness of sample | 0 |
xwidth_i | m | horiz. dimension of optional inner hollow when in cubic geometry | 0 |
yheight_i | m | vertical dimension of optional innher hollow in cubic and cyl geometry. If zero assumed == h. | 0 |
zthick_i | m | thickness of optional innner hollow when in cubic geometry | 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 |
concentric | 1 | Flag to indicate if sample is 'concentric' | 0 |
density | g/cm^3 | density of material. V_rho=density/weight/1e24*N_A. | 0 |
weight | g/mol | atomic/molecular weight of material | 0 |
barns | 1 | Flag to indicate if |F|^2 from 'reflections' is in barns or fm^2 (barns=1 for laz, barns=0 for lau type files). | 1 |
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 |
PowderN.comp
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[ Identification | Description | Input parameters | Output parameters | Links ]
Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Thu Feb 10 12:52:12 2011