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<title>GAMGI Tutorials: Occupancy rules</title>
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<h1>Occupancy rules</h1>
<div id="notebook">
<ul>
<li><a href="occupancy_page1.html">Page 1</a></li>
<li><span>Page 2</span></li>
</ul>
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<div class="contents">
<h3>Conventional volume</h3>
<ol>
<li>
Press <b>Cell->Remove</b> and press over the cell to remove it.
Press <b>Cell->Create</b> and set <b>System</b> to <b>c</b>, <b>Lattice</b>
to <b>P</b> and the lattice parameter <b>a</b> to <b>1</b>.
In the <b>Type</b> page, set the number of conventional cells
to <b>5</b>, <b>5</b>, <b>5</b>, and press <b>Ok</b> to create
the cell. Press <b>Save</b> and then <b>Ok</b>, to save the empty
cell.</li>
<li>Repeat the <b>Cell->Link</b> task, linking the cell volume
with the Si atom, with the pattern (<b>*2_</b>, <b>*</b>, <b>*</b>).
The left side of the cell is occupied with Si atoms. Repeat the
<b>Cell->Link</b> task, this time linking with a C atom, with
the pattern (<b>_2*</b>, <b>*</b>, <b>*</b>). The right side
of the cell is occupied with C atoms.</li>
<li>Press <b>Save</b> and move <b>Backward</b> once, to recover the
empty cell, then press <b>Ok</b>.
To create 8 alternating octant cubes, four with Si and four with
C atoms, repeat the <b>Cell->Link</b> task 4 times with a Si atom,
with the rules
(<b>*2_</b>, <b>*2_</b>, <b>*2_</b>), (<b>_2*</b>, <b>_2*</b>, <b>*2_</b>),
(<b>_2*</b>, <b>*2_</b>, <b>_2*</b>), (<b>*2_</b>, <b>_2*</b>, <b>_2*</b>)
and another 4 times with a C atom, with the rules
(<b>*2_</b>, <b>*2_</b>, <b>_2*</b>), (<b>_2*</b>, <b>_2*</b>, <b>_2*</b>),
(<b>_2*</b>, <b>*2_</b>, <b>*2_</b>), (<b>*2_</b>, <b>_2*</b>, <b>*2_</b>).</li>
<li>Press <b>Save</b> and move <b>Backward</b> once, to recover the
empty cell, then press <b>Ok</b>.
Repeat the <b>Cell->Link</b> task, linking the cell volume
with the Si atom, with the pattern (<b>*_</b>, <b>*_</b>, <b>*_</b>).
Alternating nodes, half of the total, are now occupied with Si atoms.
Repeat the <b>Cell->Link</b> task, this time linking with a C atom,
with the pattern (<b>_*</b>, <b>_*</b>, <b>_*</b>). The other half
of the alternating nodes is now occupied with C atoms.</li>
<li>Press <b>Save</b> and move <b>Backward</b> once, to recover the
empty cell, then press <b>Ok</b>.
Press <b>Cell->Modify</b> and change, in the <b>Type</b> page,
the number of cells to <b>6</b>, <b>6</b>, <b>6</b>, in the
<b>Origin</b> page, the <b>Axes</b> to <b>Yes</b>, and press <b>Ok</b>.
The first (red), second (green) third (blue) axes are now
visible at the corner of the increased cell volume.
Press <b>Cell->Modify</b> again and change, in the <b>Origin</b>
page, the origin node coordinates to <b>3</b>, <b>3</b>, <b>3</b>,
then press <b>Ok</b>. The node origin is now at the center of the
cell volume, although the physical origin remains the same.</li>
<li>Repeat the <b>Cell->Link</b> task, linking the cell volume with
the Si atom, with the pattern (<b>*1</b>, <b>*1</b>, <b>*1</b>).
A cube with 3x3x3 nodes in the center of the cell is now occupied
with Si atoms.
Repeat the <b>Cell->Link</b> task, this time linking with a C atom,
with the pattern (<b>__****</b>, <b>__****</b>, <b>__****</b>). All nodes
around the 3x3x3 central nodes are now occupied with C atoms.</li>
</ol>
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