# Occupancy rules

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### Conventional volume

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

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