# 1: Bonding in Solids¶

## Example number 1.1, Page number 1.4¶

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

#Variable declaration
e=1.602*10**-19;   #charge of electron(c)
epsilon0=8.85*10**-12;    #permittivity(C/Nm)
r=3*10**-10;     #seperation(m)
N=6.022*10**20;
Ea=502;     #ionisation energy of A(kJ/mol)
Eb=-335;    #electron affinity for B(kJ/mol)

#Calculation
E=-e**2*N/(4*math.pi*epsilon0*r);    #electrostatic attraction(kJ/mol)
nE=Ea+Eb+E;    #net change in energy per mole(kJ/mol)

#Result
print "net change in energy per mole is",int(nE),"kJ/mol"
print "answer varies due to rounding off errors"
print "since the net change in energy is negative, the A+B- molecule will be stable"

net change in energy per mole is -296 kJ/mol
answer varies due to rounding off errors
since the net change in energy is negative, the A+B- molecule will be stable


## Example number 1.2, Page number 1.4¶

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

#Variable declaration
IPk=4.1;    #IP of K(eV)
EACl=3.6;    #EA of Cl(eV)
e=1.602*10**-19;   #charge of electron(c)
onebyepsilon0=9*10**9;

#Calculation
deltaE=IPk-EACl;
Ec=deltaE;      #energy required(eV)
R=e*onebyepsilon0/deltaE;     #seperation(m)

#Result
print "energy required is",Ec,"eV"
print "seperation is",round(R*10**9,2),"nm"

energy required is 0.5 eV
seperation is 2.88 nm


## Example number 1.3, Page number 1.5¶

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

#Variable declaration
e=1.602*10**-19;   #charge of electron(c)
epsilon0=8.85*10**-12;    #permittivity(C/Nm)
r0=236*10**-12;     #seperation(m)
N=6.022*10**20;
IP=5.14;     #ionisation energy of A(kJ/mol)
EA=3.65;    #electron affinity for B(kJ/mol)

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

#Result
print "bond energy is",round(BE,2),"eV"

bond energy is 4.61 eV


## Example number 1.4, Page number 1.18¶

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

#Variable declaration
n=9;     #born repulsive exponent
e=1.602*10**-19;   #charge of electron(c)
epsilon0=8.85*10**-12;    #permittivity(C/Nm)
r0=0.281*10**-9;     #seperation(m)
IE=5.14;     #ionisation energy of A(kJ/mol)
EA=3.61;    #electron affinity for B(kJ/mol)

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

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

cohesive energy is 7.965 eV