1: Bonding in Solids

Example number 1, Page number 1-11

In [8]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.6*10**-19;      #charge(coulomb)
epsilon0=8.85*10**-12;   
r0=236*10**-12;     #equilibrium distance(m)
I=5.14;             #ionisation energy(eV)
EA=-3.65;           #electron affinity(eV)

#Calculation
V=-(e**2)/(4*e*math.pi*epsilon0*r0);   #potential(eV)
BE=I+EA+V;          #bond energy of molecule(eV)

#Result
print "bond energy of molecule is",round(BE,1),"eV"

bond energy of molecule is -4.6 eV

Example number 2, Page number 1-11

In [11]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.602*10**-19;      #charge(coulomb)
epsilon0=8.85*10**-12;   
r0=0.314*10**-9;      #equilibrium distance(m)
A=1.75;               #madelung constant
n=5.77;               #born constant
I=4.1;                #ionisation energy(eV)
EA=3.6;               #electron affinity(eV)

#Calculation
V=-A*e**2*((n-1)/n)/(4*e*math.pi*epsilon0*r0);
CE=round(V,4)/2;    #potential energy per ion(eV)
x=(I-EA)/2;
TCE=CE+x;           #cohesive energy per atom(eV)

#Result
print "cohesive energy per atom is",TCE,"eV"
print "answer given in the book is wrong"

cohesive energy per atom is -3.0684 eV
answer given in the book is wrong

Example number 3, Page number 1-12

In [14]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.602*10**-19;      #charge(coulomb)
epsilon0=8.85*10**-12;   
r0=0.281*10**-9;      #equilibrium distance(m)
alphaM=1.748;         #madelung constant
n=9;                  #born constant

#Calculation
CE=-alphaM*e**2*((n-1)/n)/(4*e*math.pi*epsilon0*r0);    #cohesive energy per molecule(eV)

#Result
print "cohesive energy per atom is",round(CE,3),"eV"

cohesive energy per atom is -7.965 eV

Example number 4, Page number 1-12

In [16]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.6*10**-19;      #charge(coulomb)
epsilon0=8.85*10**-12;   
r0=2.5*10**-10;     #equilibrium distance(m)

#Calculation
PE=e**2/(4*e*math.pi*epsilon0*r0);

#Result
print "potential energy of system is",round(PE,2),"eV"

potential energy of system is 5.75 eV

Example number 5, Page number 1-13

In [18]:
#importing modules
import math
from __future__ import division

#Variable declaration    
e=1.6*10**-19;      #charge(coulomb)
r0=0.281*10**-9;    #equilibrium distance(m)
a=1.748*10**-28;    #madelung constant(J m**2)
n=9;                #repulsive exponent value
m=1;

#Calculations
Ur0=-a*(1-m/n)/(e*r0**m);      #cohesive energy of NaCl(eV)

#Result
print "cohesive energy of NaCl is",round(Ur0,2),"eV"

cohesive energy of NaCl is -3.46 eV

Example number 6, Page number 1-13

In [23]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.6*10**-19;      #charge(coulomb)
epsilon0=8.85*10**-12;   
r0=0.281*10**-9;    #equilibrium distance(m)
I=5.14;             #ionisation energy(eV)
EA=-3.61;           #electron affinity(eV)

#Calculation
V=-(e**2)/(4*e*math.pi*epsilon0*r0);   #potential(eV)
CE=I+EA+V;          #cohesive energy of molecule(eV)

#Result
print "cohesive energy of molecule is",round(CE,2),"eV"

cohesive energy of molecule is -3.59 eV