other along the IRC, and the changes that can be noticed are the merging of the two
disynaptic basins V 1,2 (C2,O1) into a unique disynaptic basin V(C2,O1) (cusp-type
catastrophe) when the system reaches the SSD-V. Finally the system reaches the
SSD-VI, the splitting of the V 1 (C3,O4) disynaptic basin into two disynaptic basins
V 1,2 (C3,O4) (cusp-type catastrophe) accounting for the newer double bond formation
Fig. 10.10 Snapshots of the ELF localization domains (η = 0.819 isosurface) for selected points
along the IRC from TS4: a α-lactone intermediate, belonging to SSD-I, b point at s ≈ −1.998
amu
1/2 bohr belonging to SSD-II, c point at s ≈ −0.498 amu
1/2 bohr belonging to SSD-III, d point
at s ≈ 0.498 amu
1/2 bohr belonging to SSD-IV, e point at s ≈ 1.998 amu
1/2 bohr belonging to
SSD-V, f last point of the IRC, corresponding to carbon monoxide plus formaldehyde, belonging
to SSD-VI
0
1
2
3
4
5
6
7
-4
-2
0
2
4
6
8
Basin population
Reaction coordinate
V(C2,O4)
V(C2,C3)
V(O1)
V(C2)
V(O4)
V1(C2,O1)
V1(C3,O4)
V2(C2,O1)
V2(C3,O4)
Fig. 10.11 Population evolution of some selected basins along the IRC path from TS4. Dashed
lines separate the structural stability domains found, which are indicated. V(O1) and V(O4) account
for the total population of the monosynaptic basins on the O1 and O4 atoms, respectively
10 Quantum Chemical Topology Approach …
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