Ahp3018

NH₃

(insert picture of molecule to table)

Bond Length and Angle

Optimised N-H bond length (Å)	1.01798
Optimised H-N-H bond angle (°)	105.741]

Due to a compromise between accuracy and speed of calculation, these values will have some uncertainty. Bond length is accurate to ≈ 0.01Å; bond angle is accurate to ≈ 1°

More Information

Molecule	NH3
Calculation method	RB3LYP
Basis Set	6-31G(d.p)
Final energy E(RB3LYP) (a.u.)	-56.55776873
RMS gradient (a.u.)	0.00000485
Point group	C3V

 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

Ammonia molecule

The optimisation file is linked to here

Vibrational Analysis

Wavenumber (cm-1)	1090	1694	1694	3461	3590	3590
Symmetry	A1	E	E	A1	E	E
IR Intensity (KM/mol)	145	14	14	1	0	0
						File:Ahp nh6 vib1.gif

Frequency analysis

how many modes do you expect from the 3N-6 rule? (3*4) – 6 = 6 modes Which modes are degenerate (ie have the same energy)? Both E symmetries (1694 cm^-1 and 3590 cm^-1 Which modes are “bending” vibrations and which are “bond stretch” vibrations? 1090 cm^-1 (A1) bending 1694 cm^-1 (E) stretching 1694 cm^-1 (E) bending 3461 cm^-1 (A1) stretching 3590 cm^-1 (E) stretching 3590 cm^-1 (E) stretching Which mode is highly symmetric? The mode with frequency of 3461 cm^-1 One mode is known as the “umbrella” mode, which one is this? The mode with frequency of 1090 cm^-1 How many bands would you expect to see in an experimental spectrum of gaseous ammonia? 4 bands as the last two frequencies have an intensity of zero.

Charge analysis

As nitrogen is more electronegative than hydrogen, one would expect the N atom to have a more negative charge than the H atoms.

Charge distribution

Atom	Charge	Pauling Electronegativity1
Nitrogen	-1.125	3.04
Hydrogen	+0.375	2.20

H₂

(insert picture of molecule to table)