Before you can create a new crystal structure you need to have information on the lattice and the atoms it will contain. We shall use MgO as an example. MgO is face centred cubic, space group 225 (from the international tables), lattice parameter 4.21 angstroms, with atoms at (0, 0, 0) and (0.5, 0.5, 0.5) in fractional coordinates.

1. Select New Model from the File Menu. The following panel wizard should appear
   
   
   
2. Enter a name for the structure, e.g. MgO and then click Next which become visible at the bottom left of the panel. The panel change to show the lattice choices
   
   
   
3. Select the Cubic lattice type at the right of the top widget
   
   
   
4. Select the Face centered type now visible in the second widget.
   
   
   
5. Scroll the list widget until you find space group 225 (FM-3M) and select it.
   
   
   
6. Now we have chosen the lattice, Click Next to move on to the choice of lattice parameters. A single parameter (a) will be visible for cubic space groups. Enter the value of the lattice parameter (4.21)
   
   
   
7. Click Next to confirm the lattice parameter and move on to the next step. An empty 3D viewer window will open and the New Model wizard will now allow you to select the atoms in the structure abort the creation of the new structure). The lattice panel should now disappear and the following atom panel should replace it.
   
   
   
8. Select the button for the first atom (Mg). Since the default atom preferences for DLV assume ionic values, the formal charge is automatically set to +2 and the radius to 0.65 angstroms.
   
   
   
9. Since the default coordinates, (0, 0, 0), are correct for this atom, click on the Add Atom button to accept this atom. The viewer will now draw the Mg atom in the structure.
   
   
   
10. Now select the button for the second atom (O). Defaults are again set for the formal charge and radius.
    
    
    
11. Enter the fractional coordinates of the O atom, (0.5, 0.5, 0.5) into the 3 typein widgets.
    
    
    
12. Click on the Add Atom button to accept this atom. The viewer will now add the O atom to the structure.
    
    
    
13. Select Finish to accept the completed model. The New Model wizard will disappear.

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