1. For an Na+---Cl- ion pair, attractive and repulsive energies EA and ER, respectively, depend on the distance between the ions r, and the relationships are:EA= -1.436/r andER = 7.32×10 -6/r8 For these expressions, energies are expressed in eV per Na+---Cl- ion pair, and r is the distance in nanometers. The net energy EN is the sum of the two energies. a)Superimpose on a single plot EN, EA, and ER vs. r up to 1.0 nm.
b)On the basis of this plot, determine 1) the equilibrium spacing r0 between the Na+ and Cl- ions, and 2) the magnitude of the bonding energy E0 between the two ions.
c)We discussed material thermal expansions based on similar plot in the class. If a material were being designed to demonstrate no thermal expansions, how would the energy plot look like?