The mode command defines the mode which will be used in angle
calculations.
The syntax for the mode command is:
mode value [options]
Where value
can be:
0 :
single crystal - fix the angles in a specified scattering plane 1 :
single crystal - allow movements out of the scattering plane and
calculate angles to minimize deviation from a specified plane 2 :
single crystal - allow movements out of the scattering plane and
calculate angles so as to minimize the absolute deviation of the arcs
(this is equivalent to mode 1 where the specified plane is defined by
both arcs being at 0) 3 :
power sample
options are only available for mode 0 or mode 1 and are
used to specify the scattering plane. The optional arguments can
be either of the form:
sgu
value1 sgl value2(the specified plane is defined by the
arc angles sgu=value1 and sgl=value2)
OR
spv h1 k1 l1 h2
k2 l2 (the specified plane is defined by the set of arcs that are
required to put the 2 specified vectors [(h1,k1,l1) and (h2,k2,l2)] in
the scattering plane.
NOTES:
1. For mode 0or 1 if
options are not specified to define the scattering plane then the
previously stored values will be used. However, the ubcalc
command (or the GUI interface to ubcalc) will
set the arcs automatically
provided the ubmatrix is calculated using ubcalc mode 1 or 2.
Therefore, in most cases, it is NOT NECESSARY to specify the
optional arguments and they should onlybe
used by advanced users.
2. The default
mode will either be mode 0 or mode 3
(depending on whether a single crystal or powder sample is used)
following the start of a new experiment and the
user must explicitly select mode 1 or 2 if
movements out of the scattering plane is required. This is done
intentionally to prevent movements out of the scattering plane unless
they are specifically requested.
The mode command can
also be accessed from the GUI by selecting the Sample/Mode
Information tab from the Sample
top-level tab. To change the angle calculation mode, the
green button at the bottom of the tab must be changed from "Monitoring ...
Click to allow changes" to "Changing ... click
to monitor". The required mode
is selected with the blude Mode pull-down menu and the mode
command is issued by clicking on the blue Update Parameters
button. If mode
0 or 1
is selected, 2 numerical controls will be present where the values of Upper arc (sgu)
and Lower arc
(sgl) which specify the scattering plane can be input. See note 2 above
about setting these values.
