SAS

        Item               Value     Threshold  Converged?
Maximum Force            0.000161     0.000450     YES
RMS     Force            0.000105     0.000300     YES
Maximum Displacement     0.000638     0.001800     YES
RMS     Displacement     0.000418     0.001200     YES

Low frequencies ---   -0.2456   -0.1129   -0.0054   44.0270   45.1846   45.1853
Low frequencies --- 1163.6049 1213.5924 1213.5951

Optimised BH molecule

Vibrational spectrum for BH₃

wavenumber (cm-1)	Intensity (arbitrary units)	symmetry	IR active?	type
1163	92	A2	yes	out-of-plane bend
1213	14	E'	slight	in-plane bend
1213	14	E'	slight	in-plane bend
2580	0	A1'	no	symmetric stretch
2713	126	E'	yes	asymmetric stretch
2713	126	E'	yes	asymmetric stretch

There are only 3 peaks observed in the IR spectrum, as the first frequency 1163 cm^-1 has a strong intensity. Both the second and third frequencies of 1213 cm^-1 are degenerate and have a low intensity, so they are observed as one small peak. The fourth frequency 2580 cm^-1 has no net dipole moment, so has no intensity, so is not observed. The final two frequencies at 2713 cm^-1 are degenerate and have a strong intensity, so are observed as one strong signal.

The Molecular Orbital diagram for BH₃ is shown below:

There are no real significant differences between the 'real' and LCAO molecular orbitals. Thus, qualitative MO theory is a very accurate representation of the real MOs. This is a useful way of visualising the real MOs.