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<title>GAMGI Tutorials: NaCl crystalline structure</title>
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<h1>NaCl crystalline structure</h1>
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<ul>
<li><span>Page 1</span></li>
</ul>
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<div class="contents">
The NaCl rocksalt structure is widely observed in ionic crystals,
with equal number of cations and anions, when the cation is
significantly smaller than the anion: NaCl, KCl, LiF, MgO,
CaO, SrO, NiO, CoO, MnO and PbO.
<p/>
To build this structure, first we create the cell with the
observed lattice parameters, then the Na, Cl atoms used as models,
with the observed ionic radius, and then link the cell with the
atoms.
<ol>
<li>
Press <b>Cell->Create</b> and set <b>System</b> to <b>c</b>,
<b>Lattice</b> to <b>F</b> (Face-Centered Cubic) and <b>a</b>
to <b>5.660</b> (so the ions will be in contact along <100>
directions). Press <b>Ok</b> to create the cell.
</li>
<li>
Select <b>Atom->Create</b> and set <b>Style</b> to <b>Solid</b>,
<b>Size</b> to <b>1.0</b> and <b>Variancy</b> to <b>1.0</b>.
Set <b>Element</b> to <b>Na</b>, <b>Radius</b> to <b>1.020</b>
(ionic radius for Na+) and press the mouse over the graphic
area. A Na atom is created where the mouse was pressed.
</li>
<li>
Set <b>Element</b> to <b>Cl</b>, <b>Radius</b> to <b>1.810</b>
(ionic radius for Cl-) and press the mouse over the graphic
area. A Cl atom is created where the mouse was pressed.
</li>
<li>
Press <b>Cell->Link</b> and select the <b>Crystal</b> link
method. Press the mouse over the cell, and then over the Na atom,
to identify the objects to link. Set the <b>x</b>, <b>y</b>, <b>z</b>
coordinates (<b>Position</b> page) to <b>0.5</b>, <b>0.0</b>,
<b>0.0</b> and press <b>Ok</b>. 13 Na atoms are now visible,
12 in the edges and 1 in the center, corresponding to a total
of 4 Na atoms inside the cell.
</li>
<li>
Repeat the link procedure above, but this time pressing the mouse
over the Cl atom, and setting the <b>x</b>, <b>y</b>, <b>z</b>
coordinates to <b>0.0</b>, <b>0.0</b>, <b>0.0</b>. 14 Cl atoms are
now visible, 8 in the vertices and 6 in the face, corresponding to
a total of 4 Cl atoms inside the cell.
</li>
<li>
Select <b>Light->Create</b> and press <b>Ok</b>, to add a light
and give atoms a three dimensional look.
</li>
<li>
Remove the Na,Cl atoms used as models during the building process,
pressing <b>Atom->Remove</b> and clicking the mouse over the two atoms.
</li>
<li>Rotate,move,scale the NaCl cell with the mouse. Press
<b>Atom->Measure</b> to determine lengths and angles between atoms.
</li>
<li>
Repeat the whole procedure, this time setting the cell type in
<b>Cell->Create</b> (<b>Type</b> page) to: 1) <b>Primitive</b>;
and 2) <b>Wigner-Seitz</b>.
</li>
</ol>
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