User:As11511test
Frequency analysis
In order to determine weather the obtained conformational was actually a minima, a frequency analysis must be performed to check that there are no negative frequencies. As can be seen from the tables below, there are no negative frequencies, confirming that we are at a minima.
| Vibration | Frequency / cm-1 | Intensity / ε | Symmetry (D4h p.g.) |
2 X In plane orthogonal degenerate bend  |
122 | 5.70 | Eu |
Out of plane scissoring  |
136 | 0 | A2g |
In plane scissoring  |
165 | 0 | B2g |
Wagging  |
231 | 62.85 | A2u |
Assymetric stretch of all Xe-F bonds  |
428 | 0 | B1g |
Xe-F Symmetric stretch of all bonds  |
446 | 0 | A1g |
2 X degenerate trans F-Xe-F Assymetric stretch  |
524 | 111.49 | Eu |
| Vibration | Frequency / cm-1 | Intensity / ε | Symmetry (C2v p.g.) |
Cl-Xe-f in plane bend  |
84 | 3.40 | B2 |
Cl-Xe-F out of plane bend  |
108 | 1.29 | B1 |
F-Xe-F in plane bend  |
132 | 2.80 | A1 |
In plane scissoring (all bonds) |
138 | 0.25 | B2 |
F-Xe-F out of plane bend  |
200 | 43.47 | B1 |
Cl-Xe-F asymmetric stretch |
255 | 2.79 | A1 |
F-Xe-F symmetric stretch  |
427 | 0.01 | A1 |
Cl-Xe-F asymmetric stretch |
440 | 86.37 | A1 |
F-Xe-F asymmetric stretch  |
514 | 100.73 | B2 |
Replacing a F atoms with a Cl has a significant effect on the frequencies. The lowest energy modes now correspond to vibrations involving the Cl atom, with the Cl-Xe-F in plane bend at only 84 cm-1. Interestingly the F-Xe-F in plane bend in XeF3Cl is highier in energy than then corresponding one in XeF4: 132 vs. 122 cm-1. This can be explained in terms of sterics, more energy is needed to put the F atoms next to the bulkier Cl.
| Vibration | Frequency / cm-1 | Intensity / ε | Symmetry (C2v p.g.) |
Clorine atoms in plane bend  |
78 | 1.15 | A1 |
F atoms in plane wagging |
86 | 2.18 | B2 |
F atoms twisting |
92 | 0 | A2 |
F atoms scissoring  |
128 | 0.95 | A1 |
Wagging (all molecule, F at highier amplitute)  |
143 | 28.15 | B1 |
Cl atoms asymmetric stretch  |
243 | 4.14 | B2 |
Cls Symmetric stretch  |
257 | 1.40 | A1 |
Fs symmetric stretch  |
430 | 83.07 | A1 |
Fs assymetric stretch  |
430.28 | 66.87 | B2 |
| Vibration | Frequency / cm-1 | Intensity / ε | Symmetry (D2h p.g.) |
Cl atoms in plane scissoring  |
56 | 1.56 | B2u |
Cl out of plane scissorin g |
66 | 1.09 | B3u |
F atoms rocking  |
117 | 0 | B3g |
F atoms in plane scissoring  |
141 | 1.41 | B1u |
Cls symmetric stretch  |
188 | 0 | Ag |
Fs wagging  |
189 | 33.09 | B3u |
Cls asymmetric stretch  |
279 | 30.19 | B1u |
F symmetric stretch  |
419 | 0 | Ag |
F asymmetric stretch  |
505 | 92.87 | B2u |