Simulation packages DigiSim

The question arises of how low an N value it is possible to work with and still get good results. The simulation package DigiSim due to Rudolph and Feldberg [482] routinely uses as few as 14 and is able to achieve sufficient accuracy in the current. This depends on one s definition of sufficient . If 0.1% accuracy is wanted, about 40 points in space might be optimal. 

Figure 10.1 A cyclic voltammogram, normalized to make the standard electrode potential, = 0 V. The experimental trace is shown by as a continuous line, while data calculated by the DigiSim simulation package are represented as circles. Reprinted with permission from Current Separations, Vol. 15(2), 67-71, copyright Bioanalytical Systems, Inc. 1996.

The programs described above are limited in scope, and a superior approach is to employ a simulation package. There are three commercial programs at the forefront of the market, namely DigiSim, Condecon and GPES. 

The DigiSim simulation package was compiled by Manfred Rudolph and Stephen Feldberg, in collaboration with Bioanalytical Systems, Inc. (BAS). 

Carlo Nervi considers DigiSim to be presently the best simulation package available , even though he has produced a package of his own, namely ESP, as described below. 

Although the theoretical basis of the technique is different from other electrochemical-simulation packages, in operation it is just as powerful as DigiSim, allowing parameters to be computed for a variety of mechanisms, electrode geometries and experiment types. More information and representative references to Condecon, can be found at its website ... 

Wfe can be satisfied that the variables we have (e.g. A, D, etc., as above) are accurate if they allow us to model a system precisely. Vie say that the variables fit the data. Figure 10.1 shows a cyclic voltammogram (CV), with superimposed on this current-potential data simulated with the DigiSim package (as described in more detail below). The fit between theory and experiment is seen to be good, so we say that the derived variables fit the data. 

The DigiSim program probably represents the current state of the art which is achievable for simulating and analysing cyclic voltammograms. This package can perform cyclic voltanunetry for a wide range of mechanisms at planar, spherical, cylindrical or rotated disc electrodes. It also computes concentration profiles. 

Figure 10.3 shows the CV of a nickel(n) complex as a function of scan rate (continuous lines), together with data simulated by the DigiSim package (solid and open circles). The agreement between experiment and theory is seen to be very close. 

While several sample programs are available, nowadays a preferred and simpler process is to simulate the system via the use of more sophisticated packages such as DigiSim, Condecon or GPES. 

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