UB Matrix for Triple Axis Instruments

> CELL a b c alpha beta gamma

set unit cell constants. If b or c are omitted, the same value as for a is used, if angles are omitted, they are set to 90 degress. Without arguments, the cell constants are listed.

> PEAK qh qk ql a4 a3 sgl sgu

Make an entry in the list of peaks. For angles not given, the current motor positions are used. If the given qhkl triple already exists, its list entry is overwritten. If not, a new entry is made, and the new peak name is returned. Peak names are single letters starting from A. It is therefore possible to save the information about up to 26 reflections.

> PEAK peak qh qk ql a4 a3 sgl sgu

The same as above, but a named entry is overwritten. If another entry with the same qhkl triple already exists, it is deleted.

> PEAK CLEAR peak

Remove the named peak.

> REAK CLEAR

Remove all peaks.

> CALCUB peak1 peak2

Calculate and print out the UB matrix. peak1 is used as the main peak, i.e. driving to the angles given for this peak will correspond to a QHKL which may only differ by a scalar factor of about one, if the cell constants are not correct. peak2 is used only for determining the scattering plane.

It has to be checked that this is fully compatible with the TASMAD specification. In principle, AX,AY,AZ should correspond to peak1 and BX,BY,BZ to peak2.

> CALCUB peak1 peak2 CHEAT

The same as above, but the cell constants a, b and c are scaled in order to make peak1 perfectly fitting.

> CALCUB peak1 peak2 peak3

The cell constants are calculated back from the three peaks and printed out.

> MAKEUB peak1 peak2 ...

Calculate the UB matrix and make it active. The arguments are the same as in CALCUB.

> MAKEUB

Without arguments, the last UB matrix calculated by CALCUB is used.

> LISTUB

List the UB matrix, the cell constants and all stored reflections.

Example session: (Some numbers might not be correct, as this module does not yet work in this form).

> CELL 2.88 2.88 2.88 90 90 90

Find the peak 2 0 0 and optimize it. Once we are at the maximum:

> PEAK 2 0 0
Peak   QH     QK     QL      A4      A3     SGL     SGU
A    2.00   0.00   0.00   65.31  -87.21    1.25   -5.22

Find the peak 0 4 4 and optimize it. Once we are at the maximum:

> PEAK 0 4 4
Peak   QH     QK     QL      A4      A3     SGL     SGU
B    0.00   4.00   4.00   65.31  -87.21    1.25   -5.22
> LISTUB
Cell   2.88  2.88  2.88  90.00 90.00 90.00
Peak   QH     QK     QL      A4      A3     SGL     SGU
A    2.00   0.00   0.00   65.31  -87.21    1.25   -5.22
B    0.00   4.00   4.00   99.45   20.39    4.25   -1.22
UB   1.000   0.000   0.000
     0.000   1.000   0.000
     0.000   0.000   1.000

UB matrix is not yet defined

> CALCUB A B
UB   2.456   0.530  -0.200
    -0.530   2.456  -0.090
     0.200   0.090   2.456
Peak   QH     QK     QL      A4      A3     SGL     SGU     QH     QK     QL
A    2.00   0.00   0.00   65.31  -87.21    1.25   -5.22   2.03   0.00   0.00
B    0.00   4.00   4.00   99.45   20.39    4.25   -1.22   0.02   3.95   4.03
;:the last 3 columns are the Q values calcualted back from the angles
> MAKEUB
> DR QH 2.03 0.00 0.00
> PR A4 A3 SGL SGU
A4 =  65.311
A3 = -87.215
SGL =  1.258
SGU = -5.217