Rep:Mod:SPK2497

BH3

Method- B3LYP

Basis Set- 3-21G level

        Item               Value     Threshold  Converged?
Maximum Force            0.000049     0.000450     YES
RMS     Force            0.000032     0.000300     YES
Maximum Displacement     0.000195     0.001800     YES
RMS     Displacement     0.000128     0.001200     YES

Link to the frequency file- Media:SK_BH3_FREQ.LOG

Low frequencies --- -0.2279 -0.0081 -0.0008 22.0037 22.0049 24.0346
Low frequencies --- 1163.1731 1213.2725 1213.2727

Optimised BH3 Molecule

Vibrational spectrum for BH₃

wavenumber (cm-1	IR active?	type
1163	yes	symmetric bend
1745	yes	asymmetric bend
1745	yes	asymmetric bend
3390	no	symmetric stretch
3543	yes	asymmetric stretch
3543	yes	asymmetric stretch

There are only 3 peaks in the vibrational spectrum, while there are 6 vibration because there are 2 sets of degenerate vibrations ( asymmetric bend and asymmetric stretch), 1 unique vibration ( symmetric bend) and a vibration which doesn't result in a change of dipole, therefore is not detected (symmetric stretch).

Molecular orbital Diagram

Reference- Hunt Research Group. Molecular Orbitals of BH3. Available from: http://www.huntresearchgroup.org.uk/teaching/teaching_comp_lab_year2a/Tut_MO_diagram_BH3.pdf. [ Accessed 2nd May 2019]

The main difference between the real and LCAO MOs is that in the real MOs, parts of orbitals with the same phase are combined together, whereas in LCAO they are separate. Overall, qualitative MO theory doesn't necessarily give us an accurate depiction of what real MOs look like although it is a useful tool.

Clear representation of all of the relevant MOs on the diagram. Good attempt at considering the differences between the approaches but the idea isn’t quite correct as the LCAOs are just drawn that way by convention as we draw each of the fragments. The overall MO shape itself should arise from you considering the relative in-phase and out-of-phase additions and cancellations from the fragments. Smf115 (talk) 22:29, 13 May 2019 (BST)

Association Energy of Ammonia Borane

E(NH3)= -56.56 AU

E(BH3)= -26.62 AU

E(NH3BH3)= -83.22 AU

ΔE=E(NH3BH3)-[E(NH3)+E(BH3)] = -0.04AU= -105.02 kJ/ mol - this implies that the B-N bond is a weak bond.

Correct calculation but sadly you rounded the energies too early (also to the wrong degree of accuracy) which arose in the wrong answer. No literature values are used to compare to your answer meaning that you have no evidence to conclude that it is a weaker bond. Smf115 (talk) 22:30, 13 May 2019 (BST)

NI3

Link to NI3 File- Media:NI3_OPT.LOG

        Item               Value     Threshold  Converged?
Maximum Force            0.000061     0.000450     YES
RMS     Force            0.000037     0.000300     YES
Maximum Displacement     0.000459     0.001800     YES
RMS     Displacement     0.000285     0.001200     YES

Optimised NI3 Molecule

Optimised NI3 distance- 2.18398 Å

Overall, an ok effort at the first section but largely unfinished and the NH3, NH3BH3 and NI3 frequency calculations are missing. It would have been good to see some attempt at the project section. Smf115 (talk) 22:30, 13 May 2019 (BST)