Confused About Van der Waals' & Ionic Solids

[geoffreythelm]

Homework Statement

Homework Equations

The Attempt at a Solution

I think Graphite is a Van der Waals' Solid and, er, salt would be an ionic.
But I really don't have much of a clue about what the second part is going on about!

Thanks! :)

 

[jpreed]

Can't see the attachment yet. While Coulomb interaction dominate the interplay between electrons in graphite, I do believe the force holding the layers together could be referred to as van der Waals.

 

[Fightfish]

The second part is asking you for the variation of potential (attractive term) with respect to the distance between the particles, so for the van der Waals' forces, the Lennard-Jones potential applies, while for the ionic forces, the Coulomb potential applies. This would give $$\beta$$ as 6 for the former and 1 for the latter.