Home
High energy electron diffraction patterns, both kinematical and dynamical, are displayed under controls
gathered in this window (Fig. 1). In the kinematical approximation the intensity of the spots
and lines is proportional to their structure factor. When dynamical calculations are performed the intensity of the
reflections is calculated by the Bloch-wave method. All the drawing controls
(except the gamma control) are collected in panes.

Figure 1 SAED pattern Al14Ca12O33.
Top
Sections
Top
An experimental diffraction pattern can be loaded as a background image and the calculated one superposed for comparison (Fig. 2).
This offers a good way to figure out the camera length matching the experimental one.

Figure 2 GaN (experimental and calculated).
Top
SAED drawings of Ti5O5 structure (Fig. 3a) will be demonstrated in this help file (Fig. 3b).

|
 |
Figure 3a 3-D siaplay of Ti5O5. |
Figure 3b Diffraction Ti5O5 [001]. |
The arrows and reset tools are moving the CLC or the position of the transmitted beam (000).
(green cross) or the pattern center (blue cross). The drawing can be rotated with the control of the Orientation
tabbed pane (Fig. 4a).
Moving the CLC or pattern center is also done by dragging these crosses. The popup menu attached to the drawing
allows to switch between the blue and green crosses.

|

|
Figure 4a Rotation of SAED drawing. |
Figure 4b Pop-up menu attached to the drawing. |
The popup menu allows to add Kikuchi (Fig. 5a) or HOLZ
(Fig. 5b) lines to the drawing, to index (hkl) reflections and lines (Fig. 6)
or to plot double diffraction spots (Figures 7a, 7b) as well as to send or
load a drawing to/from the clipboard.

|

|
Figure 5a Kikuchi lines. |
Figure 5b HOLZ lines (000) spot magnified 10 times. |

Figure 6 Kikuchi and HOlZ lines with (hkl) indices.

|

|
Figure 7a SAED Ti5O5 [001]. |
Figure 7b SAED Ti5O5 [001] with double diffraction spots. |
Top
The crystal orientation is changed by:
The crystal orientation will be [340, 323, 320] i.e. close to [1,1,1]! jems uses always
the indices of closest small indices zone axis (here [1,1,1]) and the indices of
the CLC (here (8, -7, -1)). Note that the CLC is always perpendicular to the zone axis:
[uvw] · (hkl) = 0.

|

|
Figure 8a Selecting [111] zone axis. |
Figure ba Moving CLC at (8, -7, -1). |
For fine adjustment use:
- Shift + arrows, Alt + arrows or Ctrl + arrows.
- Shit + Ctrl + arrows, Shift + Alt + arrows, Ctrl + Alt + arrows.
- Shift + Ctrl + Alt + arrows.
- Shift + Ctrl + Alt + home to reset CLC to (0,0,0).
Note that the control (Shift, Ctrl, ...) key actions depend on the operating system.
Top
The table of [uvw] zone axes can be one entry at a time. When many rows are selected at once an atlas of
SAED pattern can be produced either as a .pdf file
(Ti5O5Atlas) or a series of images (Fire).

|

|

|

|
Figure 10a Selected zone axis. |
Figure 10b SAED. |
Top
When several High Order Laue Zones are plotted, the intersection of Kikuchi bands can be indexed with
a mouse click on the diffraction pattern (Fig. 11). Then a mouse click on a pole
will align the crystal along the selected zone axis (Fig. 12). Note that the reflections
are colored (red, green, blue, ...) for ZOLZ = 0, FOLZ = 1, SOLZ = 2, ...

Figure 11 Indexing the poles near [2,1,3] with a mouse click.

Figure 12 Selecting the [3,1,5] pole.
Top
Precession diffraction pattern are simulated by activationg the
tool button
after moving the Center of Laue Circle a couple of degrees out of the zone axis direction
(Fig. 13). The
tool button also stops the precession.
When the Center of Laue Circle is (000) an SAED pattern image is shown.
The precession electron diffraction technique is able to produce perfectely symmetrical SAED patterns even when the crystal is slightly out
of perfect zone axis direction. Dynamical precession diffraction slightly decrease the effects due to dynamical diffraction
(multiple scattering). It allows to measure reflections intensities close to those of single scattering (kinematical diffraction).
Dynamical precession calculations are possible using the Bloch-wave method. Charge flipping method applied to dynamical
precession SAED patterns seems to be able to extract the phase of the reflections and to reconstruct the projected potential of the crystal.

|

|

|
Figure 13a Si [2,1,2], CLC (10.2, 0, -10.2). |
Figure 13b Reflections of the precession inside the annulus. |
Figure 13b Precession electron diffraction [2,1,2]. |
Top
The controls are collected in the follwing panes:
 |
 |
 |
Figure 14a Avalanche, to create SAED atlas. |
Figure 14b Crystal/Matrix, to do dynamical calculations and set the number of Laue zones . |
Figure 14b Diffraction, to adjust the diffraction paramters. |
 |
 |
Figure 15a Lattice, to modify the lattice parameters. |
Figure 15b Crystal/Matrix, to boost the intensity of the HOLZ lines. |
Top
 |
 |
Figure 16a Options, to set drawing features. |
Figure 16b Threshold, to suppress spot and lines weaker
than a threshold value. |
FOLZ correction is displayed when HOLZ are added to the SAED pattern (Fig. 17).

Figure 17 HOLZ voltage correction.
Top
 |
 |
Figure 18a Processing, to process background images. |
Figure 18b Variant, to plot diffractions of twinned crystal, variants or
epitaxial crystals. |
Background images can be enhanced by image processing (Fig. 19).

Figure 19 Processed background image with overlapping SAED drawing (GaN [120]).
Top
The Variant panes are enabled when overlapping crystal is loaded (Fig. 20).
 |
 |
Figure 20a Si [1,1,0] FCC twins. |
Figure 20b Si [0,1,2] FCC twins. |
Top
Lists of reflections of a the diffraction pattern tabulate the structure factors and other preperties of them including
their deviation. The list can be printed.
Figure 21 Tabular list of reflections (struture factors).
Top
With the
button a
crystal structure is displayed and rotated when the CLC is dragged (Fig. 22).
Figure 22 Rotation of the crystal when dragging the CLC.