Help Window
This applet explores the c-axis
projection of ammonium oxalate monohydrate,
a=8.035 b=10.309 c=3.795 Å P21 21 2.
Partly because the c-axis is
relatively short, none of the atoms overlaps, so the molecular
structure is clear in this projection. The panels and buttons below
allow one to explore the relationship between each Fourier term, which
is derived from the diffraction pattern, and its representation in real
space.
Panels
Reciprocal Space
This panel shows a representation of
the hk0 plane for ammonium oxalate. Click on a reflection to see the
corresponding
Fourier term in real space in the
panel "Fourier term".
Fourier Term
This panel shows the real space
representation of the Fourier term given by the reflection denoted below
the panel. Notice
that when the F is negative (that is, the phase is pi), the Fourier
term is
negative (a trough) at the origin: when the F is a positive the
Fourier term value at the origin is a crest.
Sum
This panel shows the accumulated sum
of terms entered so far.
Buttons
Sum
After clicking Sum, all Fourier terms
are
summed.
Accum
Click this button repeatedly to add
one term at a time. Those already included are set red in the
reciprocal space
panel.
Fit
This toggle button shows oxalate ions,
ammonium ions and water molecules in the unit cell (and their
symmetry equivalents).
Fs
This button launchs a new window that
shows the F s. There is a slider in the new window that can be
used to change the
resolution. The reflections used in the sum are then made bold, while
those outside the limits are normal font. A choice button at the
bottom allows one to choose random phases, or random magnitudes. In
this case the Fused columns shows the F value used in the sum.
Restart
Clears all flags back to the default
when the applet was started.