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// Ex10_13 Page:224 (2014)
clc;clear;
e = 1.6e-019; // Charge on an electron, C
epsilon_0 = 8.85e-012; // Absolute electric permittivity of free space, coulomb-square/N/Sq.m
r_0 = 0.31e-009; // Equilibrium separation of Na+ and Cl- ions, m
alpha = 1.748; // Madelung constant
n = 9; // Repulsive exponent
E_ion = 5; // Ionization energy of NaCl, eV
V = -1*alpha*e^2/(4*3.14*epsilon_0*r_0*e)*(1-1/n); // Potential energy of Na+ and Cl- ions, eV
E_ele = 1/2*V; // Electron affinity, eV
E_trans = E_ion + E_ele; // Electron transfer energy, eV
delta_E = E_trans/2; // Contribution per ion to the cohesive energy, eV
E_cohesive = E_ele + delta_E; // Cohesive energy per NaCl atom, eV
printf("\nThe cohesive energy per NaCl atom = %5.3f eV", E_cohesive);
// Result
// The cohesive energy per NaCl atom = -2.911 eV
// The answers vary due to round off error
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