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Comps 2 question:

What is the energy in eV between atoms in a typical solid state material ?

Just rough estimate ?

How is that related to the thermal energy that needs to be supplied in order to melt it ?

For example a typical bond has 1eV but we need much smaller energy to break it, why is that ?

For NaCl the latice energy is 800kJ/mol which is 7eV per atom.

Where is the mistake here ?

1eV = 6.10^18 eV, 1eV = 11000K

Thanks a lot!

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I think this is a fair question. As solid state is not my field I will look around and try to understand the reason for this . I suspect that it has to do with the statistical fact that temperature is proportional to the root mean square of the kinetic energy, whereas the 1 ev to temperature is just a convention about units. – anna v Sep 25 '12 at 13:29

1 Answer

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The formation energies for solids and molecules are typically on the order of eV's per atom.

When you go from solid to liquid, you actually keep most of your bond energy because the atoms are still close to each other. This is why the melting point of NaCl (~1000 K) is much smaller than the temperature you calculated based on the lattice energy.

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