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Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ...

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3.6 Oscillating reactions* 70<br />

(5) Solution for ():<br />

() = 1 + 2 − = 0 cos (3.198)<br />

with<br />

=( 1 3 [A] 0<br />

) 12 (3.199)<br />

This means that if the system is displaced from its steady-state, the species concentrations<br />

will start to oscillate and the displacements may even grow in magnitude<br />

until the amplitude reaches the limiting value 0 (see limit cycle diagram in<br />

Fig. 3.6).<br />

I<br />

Figure 3.6: Limit cycle diagram for chemical oscillations according to the Lotka mechanism.<br />

b) The Brusselator 32<br />

Reaction scheme:<br />

<br />

A →<br />

1<br />

X (1)<br />

B+X 2<br />

→ R+Y (2)<br />

Y+2X (3.200)<br />

3<br />

→ 3X (3)<br />

<br />

X →<br />

4<br />

S (4)<br />

32 The name ‘Brusselator’ stems from the workplace of its inventor Prigogine (Brussels). The model<br />

does not correspond to a real chemical system.

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