View source for SXY19970601

=Ammonia Molecule=
==Summary of NH3==
'''After optimisation of structure of ammonia, we can measure the N-H bond length and H-N-H bond angle:'''

N-H bond length=1.01798 Å

H-N-H bond angle=105.741
<pre>
        Item               Value     Threshold  Converged?
 Maximum Force            0.000004     0.000450     YES
 RMS     Force            0.000004     0.000300     YES
 Maximum Displacement     0.000072     0.001800     YES
 RMS     Displacement     0.000035     0.001200     YES
</pre>
'''It's easy to find that the structure of NH3 is optimized because the force is nearly zero which means it's the lowest energy form of ammonia.'''
<pre>
calculation method:RB3LYP
basis set:6-31G(d,p)
final energy E(RB3LYP):-56.55776873au
point group:C3V
</pre>
<jmol><jmolApplet>
  <title>test molecule</title>
  <color>black</color>
  <size>200</size>
  <uploadedFileContents>XINYI SHEN PHUNT NH3 OPTF POP.LOG</uploadedFileContents>
</jmolApplet></jmol>


The optimisation file is liked to [[Media:XINYI SHEN PHUNT NH3 OPTF POP.LOG| here]]

===Vibration display of NH3===
[[File:Display_vibrations.png]]

'''how many modes do you expect from the 3N-6 rule?'''

'''Answer:6'''

'''which modes are degenerate (ie have the same energy)?'''

'''Answer:mode2and3, mode5and6'''

'''which modes are "bending" vibrations and which are "bond stretch" vibrations?'''

'''Answer:"bending" vibrations:mode1,2,3/"bond stretch" vibrations:mode4,5,6'''

'''which mode is highly symmetric?'''

'''Answer:mode4'''

'''one mode is known as the "umbrella" mode, which one is this?'''

'''Answer:mode 1'''

'''It has the highest intensity because of largest change in dipole moment.'''

'''how many bands would you expect to see in an experimental spectrum of gaseous ammonia?'''

'''Answer:2'''

'''Since there are four different vibration frequency, four bands are expected to to be seen in the spectrum. However, only two peaks are observed because the change in dipole moment of mode 4, mode 5 and mode 6 is very small and the intensity is too low. '''

==charge distribution of NH3==
[[File:Nh3 charges xs3015.png|500px]]
N is expected to be negatively charged, and H is expected to possess positive charges because N has larger electronegativity than H.

=H2 molecule=
==summary of H2==
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000000     0.000450     YES
 RMS     Force            0.000000     0.000300     YES
 Maximum Displacement     0.000000     0.001800     YES
 RMS     Displacement     0.000001     0.001200     YES
 Predicted change in Energy=-1.164080D-13
 Optimization completed.
</pre>
'''Structure is optimised when force equals zero.'''
<pre>
calculation method:RB3LYP
basis set:6-31G(d,p)
final energy E(RB3LYP):-1.17853936au
point group: D∞h
</pre>
===Vibration display of H2===
[[File:H2 display vibrations.png]]
'''Intensity is zero because there is no change in dipole moment.'''

==charge distribution of H2==
[[File:H2 charges xs3015.png|500px]]
'''No charge was expected on H because no difference between electronegativity'''

=N2 molecule=
==summary of N2==
<pre>
calculation method:RB3LYP
basis set:6-31G(d,p)
final energy E(RB3LYP):-109.52412868au
point group: D∞h
</pre>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000001     0.000450     YES
 RMS     Force            0.000001     0.000300     YES
 Maximum Displacement     0.000000     0.001800     YES
 RMS     Displacement     0.000000     0.001200     YES
 Predicted change in Energy=-3.401002D-13
</pre>
===Vibration display of N2===
[[File:N2 display vibrations.png]]
'''Intensity is zero because there is no change in dipole moment.'''

==charge distribution of N2==
[[File:N2 charges xs3015.png|500px]]
'''No charge was expected on N because no difference between electronegativity'''

=Enthalpy change of formation of NH3=
'''N2 + 3H2 -> 2NH3'''

E(NH3)=-56.55776873au

2*E(NH3)=-113.1155375au

E(N2)=-109.52412868au

E(H2)=-1.17853936au

3*E(H2)=-3.53561808au

ΔE=2*E(NH3)-[E(N2)+3*E(H2)]=-0.05579074au=-146.478599028 KJ/mol

'''The enthalpy change is negative, therefore exothermic reaction and the ammonia product is favoured.'''
=HCL Molecule=
==Vibration display of HCL==
[[File:HCL display vibrations.png]]
'''Intensity is not zero because there is change in dipole moment.'''
==Charge Distribution of HCL==	
[[File:HCL Charges xs3015.png|500px]]
'''Cl atom is negatively charged due to higher electronegativity than H, and H atom is positively charged.'''

==Molecular Orbital of HCl==

[[File:Spy orbital of Cl.png|500px]]

'''This is the 1π molecular orbital of HCl which is occupied by 2 electrons and deep in energy(-7.22836au). It is contributed by 2py atomic orbital of Cl. It is a non-bonding orbital. '''
	

[[File:2pz orbital of Cl.png|500px]]

'''This is the 3σ molecular orbital of HCl which is occupied by 2 electrons and deep in energy(-7.23847au). It is contributed by 2pz atomic orbital of Cl. It has lower energy than 1pi as a result of mixing with 1s orbital of H because of same symmetry.  It is a non-bonding orbital.'''

[[File:Sigma orbital of HCl.png|500px]]

'''This is the 4σ molecular orbital of HCl which is occupied by 2 electrons and deep in energy(-0.84773au). It is formed by mixing 3s atomic orbital of Cl and 1s orbital of H. It is a bonding orbital.'''

[[File:Sp of Cl and 1s of H.png|500px]]

'''This is the 5σ molecular orbital of HCl which is occupied by 2 electrons and deep in energy(-0.47433au). It is formed by mixing 3sp atomic orbital of Cl and 1s orbital of H . It is a bonding orbital.'''

[[File:Sp cl and 1s h antibonding.png|500px]]

'''This is the 6σ* molecular orbital of HCl which is the lowest unoccupied molecular orbital (0.01366au). It is formed by mixing 3sp atomic orbital of Cl and 1s orbital of H . It is an anti-bonding orbital. '''