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Tutorial A: Introductory Examples
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you have selected in the structure picture will be displayed with their ”space-filling” radii. The
selection frames are still present around them, so please press the <Esc> button on your keyboard
to release the selection and remove the frames (fig. 18).
Fig. 18: The atoms which have been selected in the previous step are now drawn with their ”spacefilling” radii.
Let’s summarize what we have up to now: One part of the structure picture presents the crystal structure of quartz as corner-connected SiO4 -tetrahedra, another part shows the space filling character of
the atomic arrangement. A third way to look at the crystal structure of quartz is to describe it as a
three-dimensional network of covalent bonded atoms. Hence, we will change the model for a part
of the structure picture to ”wires/sticks” to emphasize this important point of view.
Please draw a selection rectangle somewhere in the center of the picture similar to the one used
for the space-filling model (press the left mouse button, move the mouse until the selection rectangle which is displayed contains the objects you would like to select, and finally release the mouse
button).
Before we can actually change the model to ”wires/sticks”, we have to remove all polyhedra within
the selection rectangle in order to make the actual bonds visible: Please select the ”Polyhedra” command from the ”Destroy” submenu of the ”Build” menu (in short: select ”Build/Destroy/Polyhedra”
in the menu). The atoms and bonds previously hidden by the polyhedra surfaces will become visible.
Note that the atoms are still selected (fig. 19)!
Fig. 19: In the center of the structure, some polyhedra have been removed in order to make the bonds
visible.
Now, you can change the model for the selected atoms: Please open the ”Model and Radii...” dialog
from the ”Picture” menu, then select the model ”Wires/Sticks” in the combobox at the top of the
dialog. Afterwards, click ”OK” (the dialog will close) and press the <Esc> button to release the