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WT - Lattice indexing

(3/1/96)

PURPOSE

Automatically indexes a reciprocal lattice from 2 or more reflections entered. Creates a filter file for quasi-optical crystal-line Fourier filtration.

SEE ALSO

WT TV [Lattice Indexing]
GF [General Filter for quasi-optical Fourier Filtration]
GF C [General Filter- Condesnsed Fourier]
RD [ReDuce transform]

USAGE

.OPERATION: WT

.POWER SPECTRUM FILE: POW001
[Enter the name of the power spectrum file.]

.FOURIER FILE: FOU001
[Enter the name of the Fourier file.]

.WINDOW SIZES (SEARCH,FILT): 7,5
[Enter the dimensions of square windows to be used in the search for maxima and filtration (2nd not presently used).]

.LATTICE INDICES (H,K): 1,0
[Enter the lattices indices of first reflection.]

.FOURIER POSITIONS (KX,KY): 42,27
[Enter the approximate kx and ky positions (relative to 0.0 at center of Fourier transform and associated power spectrum) of the reflection associated with the above indices. The exact position of the maximum within the search window is determined and returned. Note: axes are transposed going from real to Fourier space. Real space: +x is to the right, +y is down. Fourier space: +kx is down, +ky is to the right.]

.LATTICE INDICES (H,K): 2,1
[Enter the lattice indices of the second reflection.]

.FOURIER POSITION (KX,KY): 57,30
[Enter the approximate kx,ky position of the second reflection.]

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[...continues until (0,0) is entered for Lattice Indices. A minimum of 2 reflections in linearly independent positions are required. All reflections entered will be used in a least square fit to extrapolate the reciprocal lattice.]

.MAXIMUM RESOLUTION DISTANCE: 120
[Enter the radius of a circle in Fourier space within which reflections on the indexed lattice are being deterdetermined.]

[The initial and the refined lattice parameters will be listed along with x and y components of each. A list of the reflections found, and their energies, is recorded in the RESULTS file.]

.FILTER FILE: FIL001
[Enter the name of the file that will contain the coordinates of the refined lattice for use in filtration. See 'GF' and 'RD' for details.]

NOTES

  1. A detailed description of quasi-optical filtration using SPIDER is found in the document FILTER.DOC.

SUBROUTINES

LATCEN, SOLV2D

CALLER

TVWN1

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