Periodic Boundary Conditions (PBC)

Tutorial 5 - Transform a Primitive Unit Cell of Diamond Crystal to a Face-Centered Cubic Unit Cell, PBC/3D

5-1  Follow steps 3-1 through 3-18 of PBC Tutorial 3.

5-2  Show the PBC dialog for the molecule by selecting "PBC" from the "Edit" menu of the main window.

5-3  In the "View" tab of the PBC dialog, select "Dull" from the "Replicate Contents Format" combobox .

5-4  In the "View" tab of the PBC dialog,  check the "Show All Boundary Atoms" checkbox.

5-5  In the "View" tab of the PBC dialog, show one replicate cell along the "-c" axis using the corresponding spin boxes (1 1 1 0 0 1) in the "Cell Replication" section.

5-6  In the "Cell" tab of the PBC dialog, select "Fix Contents Cartesian Coordinates" from the "Cell Changes" combobox and check the "Add / Remove" atoms checkbox.   Then push down the "Place" button and select "a (1,0,0)" instead of "0 (0,0,0)" to enable placement of the head of the "a" lattice vector at any atom selected in the view window using the mouse.  In the view window, click on the atom at position (1, 1, -1).

5-7  In the "View" tab of the PBC dialog, show zero replicate cells along the "-c" axis again, one along the "-a" axis and two along the "+b" axis using the corresponding spin boxes (1 2 1 1 0 0) in the "Cell Replication" section.

5-8  In the "Cell" tab of the PBC dialog,  select "b (0,1,0)" instead of "a (1,0,0)" to enable placement of the head of the "b" lattice vector at any atom selected in the view window using the mouse.  In the view window, click on the atom at position (-1, 2, 0).

5-9  In the "View" tab of the PBC dialog, show one replicate cell along the "+a" axis again, one along the "-b" axis and two along the "+c" axis using the corresponding spin boxes (1 1 2 0 1 0) in the "Cell Replication" section.

5-10  In the "Cell" tab of the PBC dialog,  select "c (0,0,1)" instead of "b (0,1,0)" to enable placement of the head of the "c" lattice vector at any atom selected in the view window using the mouse.  In the view window, click on the atom at position (0, -1, 2).

5-11  In the "View" tab of the PBC dialog, show just the reference cell using the corresponding spin boxes (1 1 1 0 0 0) in the "Cell Replication" section.

5-12  In the "View" tab of the PBC dialog, uncheck the "Show All Boundary Atoms" checkbox.

5-13  We now have a face-centered cubic unit cell of diamond which gives the same crystal structure as that from the primitive unit cell we started with.