Sliding activity and fugacity paths

Sliding activity and sliding fugacity paths are similar to fixed activity and fixed fugacity paths, except that the model varies the buffered activity or fugacity over the reaction path rather than holding it constant. Once the equilibrium state of the initial system is known, the model stores the initial activity a° or initial fugacity / / of the buffered species or gas. (The modeler could set this value as a constraint on the initial system, but this is not necessary.) 

The modeler supplies the final (or target) activity aj or fugacity fm, which will be achieved at the end of the reaction path, when = 1. The modeler also specifies 

on the other hand, the value s logarithm is to be varied, the model calculates the value according to 

To see the difference between sliding a value and sliding its logarithm, consider a path in which fo2 varies from one (10°) to 10-30. If A in this simple example is 0.2, the model will step along the reaction path in even steps of either fo2 or 

If we select the linear option (the center column), the path will stop at a series of oxidizing points followed by a single reducing point. If we choose the logarithmic option (right column), however, the path will visit a range of oxidation states. 

The modeler supplies the final (or target) activity a- or fugacity / , which will be achieved at the end of the reaction path, when = 1. The modeler also specifies whether the activity or fugacity itself or the logarithm of activity or fugacity is to be varied. If the value is to be varied, the model determines it as a function of reaction progress according to 

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