NH3 molecule

general imformation

N-H bond distance	1.02 ± 0.01Å
H-N-H bond angle	106± 1°
Calculation Method	RB3LYP
Basis Set	6-31G(d,p)
E(RB3LYP)	(-56.55776873 a.u.)
RMS Gradient Norm	0.00000485 a.u.
Point Group	C3V

This is my logfile

item table

 
         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

projected molecule

NH3

vibration and charge

vibration

wavenumber cm-1	symmetry	intensity
1090	A1	145.3814
1694	E	13.5533
1694	E	13.5533
3461	A1	1.0608
3590	E	0.2711
3590	E	0.2711

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

which modes are degenerate (ie have the same energy)? 1693.95cm -1 and 3589.82 cm-1

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

"bending" vibrations : 1089.54 cm-1 1693.95 cm-1

"bond stretch" vibrations : 3461.29 cm-1 and 3589.82 cm-1

which mode is highly symmetric? 3461.29 cm-1

one mode is known as the "umbrella" mode, which one is this? 1090 cm-1

how many bands would you expect to see in an experimental spectrum of gaseous ammonia? 2, because intensity of others are low

charge distribution

atom	charge
N	(-1.125)
H	0.375

note: the N is more electronegative across period table( group 15), it has high negative charge

N2

general imformation

N≡N bond distance	1.10± 0.01Å
N≡N bond angle	180°
Calculation Method	RB3LYP
Basis Set	6-31G(d,p)
E(RB3LYP)	(-109.52412868 a.u.)
RMS Gradient Norm	0.00000060 a.u.
Point Group	D∞h

this is my log file

item table

         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

projected molecule

N2

vibration and charge

vibration

wavenumber cm-1	2457
symmetry	SGG
intensity (arbitrary units)	0
image

charge distribution

atom	charge
N	(0.000)
N	(0.000)

H2

general imformation

H-H bond distance	0.74 ± 0.01Å
H-H bond angle	180°
Calculation Method	RB3LYP
Basis Set	6-31G(d,p)
E(RB3LYP)	(-1.17853936 a.u.)
RMS Gradient Norm	0.00000017a.u.
Point Group	D∞h

this is my log file

item table

        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

projected molecule

H2

vibration and charge

vibration

wavenumber cm-1	4466
symmetry	SGG
intensity (arbitrary units)	0
image

charge distribution

atom	charge
H	(0.000)
H	(0.000)

nano matel complex

there are two N-N bond within this structure. bond distances are both 0.9843 Å

optimised bond distance'(1.10Å) is longer than the crystal structure bond distance, because for the optimised bond distance is only the measure of distance of a single N2 molecule, there is no other surrounding effect to the bond distance. But in actual crystal structure, the triple bond could more stabilized by overlapping the orbital in the centre metal. [paper reference]

Energy of Haber-Bosch process

N2 + 3H2 -> 2NH3

E(NH3)= -56.5577687 a.u.

2*E(NH3)= -113.1155375 a.u.

E(N2)= -109.5241287 a.u.

E(H2)= -1.17853936 a.u.

3*E(H2)= -3.5356181 a.u.

ΔE=2*E(NH3)-[E(N2)+3*E(H2)]= -113.1155375 + 109.5241287 +3.5356181 = - 0.0557907 a.u. = - 146.82 ± 0.1 kJ/mol

the total energy of the reaction is negative, so ammonia product is more stable

SiH4 molecule

general imformation

Si-H bond distance	1.48 ± 0.01Å
H-Si-H bond angle	109 ± 1°
Calculation Method	RB3LYP
Basis Set	6-31G(d,p)
E(RB3LYP)	(-291.88802760 a.u.)
RMS Gradient Norm	0.00000002 a.u.
Point Group	TD

This is my logfile

item table

 
               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     0.000000     0.001200     YES

projected molecule

SiH4

vibration and charge

vibration

wavenumber cm-1	symmetry	intensity
919	T2	136.1485
919	T2	136.1485
919	T2	136.1485
979	E	0.0000
979	E	0.0000
2244	A1	0.0000
2254	T2	143.3961
2254	T2	143.3961
2254	T2	143.3961

charge distribution

atom	charge
Si	(0.629)
H	(-0.157)

molecular orbital

discription	image
1. unhybidised orbital from AO-2p (Si),fully occupied,3 degenerate state
2. hybidised σ orbital, form by 3s(Si) and 1s(H), in-phase overlap, fully occupied,
3. hybidised π orbital, form by 3p(Si) and 1s(H),in-phase overlap,fully occuped,LOMO, three degenerate state
4. hybidised π* antiorbital, form by 3p(Si) and 1s(H),out-of-phase overlap,unoccuped,HOMO, three degenerate state
5. hybidised σ* antiorbital, form by 3s(Si) and 1s(H),out-of-phase overlap, unoccupied

sturcture is stabilised as bonding orbitals are fully filled, antibonding is not filled.

reference[1]

Ione M. Baibich,Ian S. Butler, BRIEF INTRODUCTION TO MOLECULAR ORBITAL THEORY OF SIMPLE POLYATOMIC MOLECULES FOR UNDERGRADUATE CHEMISTRY STUDENTS 15/6/12

Marking

Note: All grades and comments are provisional and subjecct to change until your grades are officially returned via blackboard. Please do not contact anyone about anything to do with the marking of this lab until you have recieved your grade from blackboard.

Wiki structure and presentation 1/1

Is your wiki page clear and easy to follow, with consistent formatting?

YES

Do you effectively use tables, figures and subheadings to communicate your work?

YES

NH3 1/1

Have you completed the calculation and given a link to the file?

YES

Have you included summary and item tables in your wiki?

YES

Have you included a 3d jmol file or an image of the finished structure?

YES

Have you included the bond lengths and angles asked for?

YES - Someone else uploaded a file named exactly as yours, so it was replaced.

Have you included the “display vibrations” table?

YES

Have you added a table to your wiki listing the wavenumber and intensity of each vibration?

YES

Did you do the optional extra of adding images of the vibrations?

YES

Have you included answers to the questions about vibrations and charges in the lab script?

YES

N2 and H2 0/0.5

Have you completed the calculations and included all relevant information? (summary, item table, structural information, jmol image, vibrations and charges)

YES - however, you stated a bond angle for diatomic molecules. To define a bond angle a minimum of 3 atoms is needed! Someone else uploaded a file named exactly as yours, so your display vibrations table was replaced.

Crystal structure comparison 0.5/0.5

Have you included a link to a structure from the CCDC that includes a coordinated N2 or H2 molecule?

YES

Have you compared your optimised bond distance to the crystal structure bond distance?

YES

Haber-Bosch reaction energy calculation 1/1

Have you correctly calculated the energies asked for? ΔE=2*E(NH3)-[E(N2)+3*E(H2)]

YES

Have you reported your answers to the correct number of decimal places?

YES

Do your energies have the correct +/- sign?

YES

Have you answered the question, Identify which is more stable the gaseous reactants or the ammonia product?

YES

Your choice of small molecule 3.5/5

Have you completed the calculation and included all relevant information?

YES

Have you added information about MOs and charges on atoms?

You have done a good job of presenting this information, well done! You should have explained the charges using an electronegativity argument. You should have analysed the computed vibrations as you did for NH3! You correctly identified unoccupied and occupied MOs and the AOs contributing to the MOs! - good job! However you missed to give the relative energies, state if each MO is bonding, anti-bonding or non-bonding. You messed up the labels of the HOMO and LUMO!

Independence 0/1

If you have finished everything else and have spare time in the lab you could: Check one of your results against the literature, or Do an extra calculation on another small molecule, or Do some deeper analysis on your results so far

NO - No independent work has been identified.