In the previous note, the protocol for defining a mechanism and the associated parameters in DigiSim® was discussed. Once the parameters have been successfully entered, a simulation can be run, using Simulation in the Run menu. The simulation for a reversible process is shown in F1.
Figure 1. Simulation of a reversible process.
The coordinates of the maxima and minima can be found using Min/Max in the Active Curve sub-menu of the View menu or the Toolbar sub-menu of the Display menu. The area for peak analysis must be defined using the mouse by clicking the left mouse button at one corner of the region, holding down the mouse button whilst dragging the mouse to the opposite corner, and then releasing. A region of the CV can be expanded by selecting Zoom from the View menu or the Toolbar (the region is then defined by dragging the mouse in the way described above); this operation is reversed using Unzoom. There are a number of parameters in the Preferences dialog box (also in the View menu) that control the appearance of the simulated voltammogram(s) (F2). It can be drawn as a series of points (Plot points) or as a line (Plot lines), the polarity of the axes can be changed (Classical or IUPAC), and either the Total current or the Current density can be plotted. The colors of voltammogram and the background can be varied using Colors.
Figure 2. Preferences dialog box - Current-Display.
Multiple voltammograms can also be displayed. After the first simulation has been run, click Duplicate in the Edit menu to return to the CV-Properties dialog box while retaining the first simulation in the temporary memory. When the parameters for the second simulation have been entered, this simulation is run, and both simulations are then displayed. Three voltammograms for the EC mechanism defined in the previous note are shown in F3 (for kf = 0, 1, and 10 s-1).
Figure 3. Simulation of an EC simulation for different values of kf.
When more than one voltammogram is displayed, one of these is specified as the Active CV (as the Min/Max function can only operates on one voltammogram), and is shown in a different color. The next voltammogram in the stack can be selected as the Active CV using Activate Next CV in the View menu. The Active CV can be deleted using Delete in the Edit menu (if this item is selected, the option of saving the simulation is also given).
There are two options for saving the simulation. The mechanism, parameters, and current/potential couples can be saved in a .cvs file using standard Windows functions, or the displayed graphic can be saved as .wmf file (using Save Screen Display in the File menu).
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