[ Identification | Description | Input parameters | Links ]
PowderN ComponentGeneral powder sample with many scattering vectors possibility for intrinsic line broadening incoherent background ratio is computed from material datafile. No multiple scattering. No secondary extinction. Based on Powder1/Powder2/Single_crystal. Geometry is a powder filled cylinder, sphere, box or any shape from an OFF file. 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' and 'focus_flip'). 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. Sample shape: Sample shape may be a cylinder, a sphere, a box or any other shape. box/plate: xwidth x yheight x zdepth (thickness=0) hollow box/plate:xwidth x yheight x zdepth and thickness>0 cylinder: radius x yheight (thickness=0) hollow cylinder: radius x yheight and thickness>0 sphere: radius (yheight=0 thickness=0) hollow sphere: radius and thickness>0 (yheight=0) any shape: geometry=OFF_file The complex geometry option handles any closed non-convex polyhedra. It computes the intersection points of the xray with the object transparently, so that it can be used like a regular sample object. It supports the PLY, OFF and NOFF file format but not COFF (colored faces). Such files may be generated from XYZ data using: qhull < coordinates.xyz Qx Qv Tv o > geomview.off or powercrust coordinates.xyz and viewed with geomview or java -jar jroff.jar (see below). The default size of the object depends of the OFF file data, but its bounding box may be resized using xwidth,yheight and zdepth. If you use this component and produce valuable scientific results, please cite authors with references bellow (in Links). Example: PowderN(reflections = "c60.lau", d_phi = 15 , radius = 0.01, yheight = 0.05, Vc = 1076.89, delta_d_d=0, DW=1) Powder definition file format Powder structure is specified with an ascii data file 'reflections'. The powder data are free-text column based files. The reflection list should be ordered by decreasing d-spacing values. ... d ... F2 Lines begining by '#' are read as comments (ignored) but they may contain the following keywords (in the header): #Vc#Debye_Waller #delta_d_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, by defining signification of the columns as a vector of indexes in the order format={j,d,F2,DW,delta_d_d/d,1/2d,q,F} Signification of the symbols is given below. Indices start at 1. Indices with zero means that the column are 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} 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 Last, CIF, FullProf and ShelX files can be read, and converted to F2(hkl) lists if 'cif2hkl' is installed. The CIF2HKL env variable can be used to point to a proper executable, else the McCode, then the system installed versions are used. 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, thickness = 0.001, concentric = 1, p_interact=0.1) 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.) The concentric arrangment can not be used with OFF geometry specification. This sample component can advantageously benefit from the SPLIT feature, e.g. SPLIT COMPONENT pow = PowderN(...)
| Name | Unit | Description | Default | |
| reflections | str | Input file for reflections (LAZ LAU CIF, FullProf, ShelX). Use only incoherent scattering if NULL or "". | "NULL" | |
| material | Be.txt | File where the material parameters for the absorption may be found. Format is similar to what may be found off the NIST website. | "NULL" | |
| geometry | str | Name of an Object File Format (OFF) or PLY file for complex geometry. The OFF/PLY file may be generated from XYZ coordinates using qhull/powercrust. | "NULL" | |
| format | {} | Name of the format, or list of column indexes (see Description). N.b. no quotes! | {0,0,0,0,0,0,0,0} | |
| mat_format | {} | Format of the asorption parameter file. | {0,0,0,0,0} | |
| radius | m | Outer radius of sample in (x,z) plane. | 0 | |
| yheight | m | Height of sample y direction. | 0 | |
| xwidth | m | Horiz. dimension of sample, as a width. | 0 | |
| zdepth | m | Depth of box sample. | 0 | |
| thickness | m | Thickness of hollow sample. Negative value extends the hollow volume outside of the box/cylinder. | 0 | |
| pack | 1 | Packing factor | 1 | |
| Vc | AA^3 | Volume of unit cell=nb atoms per cell/density of atoms. | 0 | |
| delta_d_d | AA | Global relative Delta_d/d spreading when the 'w' column is not available. Use 0 if ideal. | 0 | |
| p_inc | 1 | Fraction of incoherently scattered rays. | 0.1 | |
| p_transmit | 1 | Fraction of transmitted (only attenuated) rays. | 0.1 | |
| DW | 1 | Global Debye-Waller factor when the 'DW' column is not available. Use 1 if included in F2. | 0 | |
| nb_atoms | 1 | Number of sub-unit per unit cell, that is ratio of sigma for chemical formula to sigma per unit cell. | 1 | |
| d_omega | deg | Horizontal focus range (only for incoherent scattering), 0 for no focusing. | 0 | |
| d_phi | deg | Angle corresponding to the vertical angular range to focus to, e.g. detector height. 0 for no focusing. | 0 | |
| tth_sign | 1 | Sign of the scattering angle. If 0, the sign is chosen randomly (left and right). ONLY functional in combination with d_phi and ONLY applies to bragg lines. | 0 | |
| p_interact | 1 | Fraction of events interacting with sample, e.g. 1-p_transmit-p_inc. | 0 | |
| concentric | 1 | Indicate that this component has a hollow geometry and may contain other components. It should then be duplicated after the inside part (only for box, cylinder, sphere). | 0 | |
| density | g/cm^3 | Density of material. 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 | |
| focus_flip | 1 | Controls the sense of d_phi. If 0 d_phi is measured against the xz-plane. If !=0 d_phi is measured against zy-plane. | 0 |
| AT ( | , | , | ) RELATIVE | |||
|---|---|---|---|---|---|---|
| ROTATED ( | , | , | ) RELATIVE |
PowderN.comp.
[ Identification | Description | Input parameters | Links ]
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