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· The Ions can interact through the attractive Coulomb term
to reduce the total energy of the two ion system and form a stable molecule.
· For NaCl the binding energy of the ion pair due to
the coulomb attraction is - 8.85 eV at r0, the equilibrium spacing
of the ions.
· The Repulsive term in the potential is due
to the Pauli
exclusion principle interaction between the full
ionic quantum states. This term prevents the ion pair from collapsing to zero
dimension and has a value of +1.02 eV at r0.
·
In addition
to these major terms in the interionic interaction a van der Waals bonding
contribution of - 0.125 eV and a zero
point energy repulsive contribution
of +0.075 eV should be included.
· For NaCl, the total
cohesive energy is the sum of these component terms and has the value: Cohesive Energy
= - 7.9 eV |
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