Table 5. Definition of Symmetry Coordinates for a Trigonal Bipyramidal 6-Atom Fragment; Atom Numbers Defining Stretching Coordinates, and Letters Denoting Angle-Bending Coordinates, Are As in Figure 8a.
| symmetry coordinate | linear combination of valence coordinates |
|---|---|
| in-plane SCαO bending | a – b – c + d – e – f |
| out-of-plane SCαO bending | b – c + e – f |
| umbrella | a + b + c – d – e – f |
| CαH3 rocking | h – i |
| CαH3 twisting | b – c – e + f |
| CαH3 tilting | –a + b + c + d – e – f |
| CαH3 scissoring | g – h – i |
| sym SCα/CαO stretch | (1–2) + (2–6) |
| asym SCα/CαO stretch | (1–2) – (2–6) |
| sym CαH3 stretch | (2–3) + (2–4) + (2–5) |
| asym CαH3 stretch (a′) | (2–3) – (2–4) – (2–5) |
| asym CαH3 stretch (a″) | (2–4) – (2–5) |
a
Linear combinations are qualitatively correct but do not show the coefficients for valence-coordinate displacements.