1: Bonding in Solids

Example number 1.1, Page number 10

In [1]:
#importing modules
import math
from __future__ import division

#Variable declaration    
e=1.6*10**-19;      #charge(coulomb)
x=9*10**9;          
r0=2.81*10**-10;    #equilibrium distance(m)
A=1.748;      #madelung constant
n=9;       #repulsive exponent value

#Calculations
U0=-(x*A*e/r0)*(1-1/n);       #potential energy(eV)

#Result
print "potential energy is",round(U0/2,3),"eV"

potential energy is -3.981 eV

Example number 1.2, Page number 10

In [2]:
#importing modules
import math
from __future__ import division

#Variable declaration    
e=1.6*10**-19;      #charge(coulomb)
x=9*10**9;          
r0=3.56*10**-10;    #equilibrium distance(m)
A=1.763;      #madelung constant
n=10.5;       #repulsive exponent value
IE=3.89;      #ionisation energy(eV)
EA=-3.61;     #electron affinity(eV)

#Calculations
U0=-(x*A*e/r0)*(1-1/n);       #ionic cohesive energy(eV)
U=U0+IE+EA;               #atomic cohesive energy(eV)

#Result
print "ionic cohesive energy is",round(U0,2),"eV"
print "atomic cohesive energy is",round(U,2),"eV"

ionic cohesive energy is -6.45 eV
atomic cohesive energy is -6.17 eV

Example number 1.3, Page number 11

In [3]:
#importing modules
import math
from __future__ import division

#Variable declaration    
N=6.02*10**26;           #Avagadro Number
e=1.6*10**-19;      #charge(coulomb)
x=9*10**9;          
r0=0.324*10**-9;    #equilibrium distance(m)
A=1.748;      #madelung constant
n=9.5;       #repulsive exponent value

#Calculations
U0=(A*e*x/r0)*(1-1/n);     
U=round(U0,2)*N*e*10**-3;      #binding energy(kJ/kmol)

#Result
print "binding energy is",int(U/10**3),"*10**3 kJ/kmol"
print "answer in the book varies due to rounding off errors"

binding energy is 669 *10**3 kJ/kmol
answer in the book varies due to rounding off errors