Giant covalent structure

Most substances with giant covalent structure do not have van der Waals’ forces.

However, if the giant covalent structure consists of LAYER structure, there are van der Waals’ forces between the layers of atoms.
Graphite is typical example of giant covalent structure with layer structure. In graphite, the carbon atoms joined together in a triangular shape with three carbon atoms, and huge layers of carbon atoms are formed in this way. The layers of carbon atoms are thought to be as parallel planes, and the adjacent layers of carbon atoms are held together by van der Waals’ forces.

2008-03-21 23:16:12 補充：
The following webpage shows the van der Waals' forces in graphite:

http://www.substech.com/dokuwiki/lib/exe/fetch.php?w=&h=&cache=cache&media=graphite_structure.png

2008-03-21 23:29:23 補充：
Three points must be noted :

(1) In diamond, each carbon atom is bonded tetrahedrally, but there is NO GIANT TETRAHEDRON.

2008-03-21 23:29:40 補充：
(2) NOT all substances with giant structure have structure like diamond. Some substances with gaint structure, e.g. graphite, have different structure (giant covalent structure consisting of layers of atoms).

2008-03-21 23:29:46 補充：
(3) If the giant covalent structure consists of layers of atoms, the atoms are joined together by covalent bonds to form layers of atoms, and the layer of atoms are held together by van der Waals' forces.

There is no van der Waals' forces in giant covalent strucutures
because the atoms are joined by strong covalent bonds
to form a continuous giant structure.
We cannot find van der Waals' forces in graphite
because graphite is a giant covalent structure
formed by numerous carbon atoms into a giant tetrahedron.

no,you can not find the find van der Waals' forces in giant covalent structure.
you just can find it in single covalent structure and simple molecular structure.