DigiElch 7 - Overview
DigiElch 7 is a Windows program that computes the electrical current, the
concentration profiles and the surface concentrations for any use-defined
mechanism comprising an arbitrary number of charge-transfer steps and first- or
second-order chemical reactions. The program works for the most common electrode
geometries including the simulation of thin layer cell experiments and the exact
(two-dimensional) simulation of the electrical current response at band and disk
micro-electrodes. Moreover, effects such as adsorption, IR-drop and/or double
layer charging can be included in all these simulations. Version 7 includes
simulation modules for the following electrochemical methods
- Cyclic Voltammetry (CV)
- Square-Wave Voltammetry (SW)
- Chrono-Amperometry (CA)
- Multi-sine Impedance (IMP)
- Fourier-Transform Cyclic Voltammetry (FT)
- Modules for conducting CV, SW, CA, IMP and FT - experiments using a
Gamry
Reference 600 potentiostat
This enables the user to do measurements and simulations for the supported
electrochemical methods in a perfectly consistent way requiring no data export
or import. Real experimental current curves (stored as E/I- or t/I-couples in
ASCII-files) can be imported into DigiElch and compared with simulated ones. The
determination of the thermodynamic and kinetic parameters involved in the
underlying reaction scheme can be accomplished in this way either by "trial and
error" ( DigiElch-Standard) or by making use of the
non-linear fitting procedure implemented into DigiElch
-Professional.
DigiElch - Standard
- Very fast and accurate simulation of the current response
for any user-defined mechanism that can be composed of charge-transfer steps and
first- or second-order chemical reactions.
- 1D simulation of finite- and semi-infinite diffusion
processes for the most common regular 1D-electrode geometries.
- Real 2D-simulations of such user-defined mechanisms for
the band and disk electrode.
- Inclusion of IR-drop and double layer charging where the
dependency of the double layer capacity from the electrode potential can be
expressed by a fourth-order polynomial.
- Simulations of termolecular charge-transfer reactions
which play an importent role in the Concerted Proton
Electron Transfer (CPET) reactions of the type
Ox + HA + e = HRed + A-
- Simulation of adsorption processes
where
- the kinetic of the adsorption processes can be formulated in a way that
leads to the Frumkin isotherm under equilibrium
conditions
- CT-reactions may proceed either by direct electron transfer of the
adsorbed species or via the desorption pathway
- the heterogeneous rate constants of any CT-reaction can be linked to
the surface coverage of a particular species.
In this way, CT-reactions proceeding with different
speed through the uncovered and covered part of the electrode can be simulated.
- reactions between adsorbed and desorbed species can be taken into
consideration
- Two different simulation methods:
- A very fast "fixed grid simulator" providing extremely high exponential
convergence towards zero for the simulated flux error.
- A relatively slow "adaptive grid simulator" that may be useful for
simulating accurate concentration profiles and/or for checking
the accuracy of the fixed grid simulator by an
independent method.
- Options for displaying how the concentration profiles are
changing in the course of the simulation.
- Options for displaying how surface concentrations or
surface coverage are changing in the course of the simulation.
- Options for displaying the fundamental-, second and
third-harmonics involved in the FT-CV current curve
- Options for displaying the envelope of the fundamental-, second
and third-harmonics involved in the FT-CV current curve
- Option for displaying a user-defined harmonics involved in the
FT-CV current curve and the envelope of the user-defined harmonics
- Options for customizing colors and style of the screen
display.
- Multi-core CPU support (process parallelization) for Data
Fitting and 2D (micro-electrode)-simulations
- Export of the screen display in Windows enhanced meta
file (*.emf) format.
- Export of simulated current curves and concentration
profiles into ASCII-files. Several formatting options which enable the exported
data to be imported into third-party presentation software.
- Import of experimental (or re-import of simulated)
current curves. In this way (and by using the Copy/Paste command) any number of
such curves can be simultaneously displayed on the screen for studying the
effect of parameter variations simulated curves or for determining parameters
yielding the "best fit" between experimental and simulated curves using a "trial
and error" strategy.
- User defined import filters for importing experimental
ASCII-data files produced by third-party instruments into DigiElch
DigiElch - Professional
-
Same features
as reported above for DigiElch-Standard. Additionally, a non-linear regression
procedure can be used for determining the thermodynamic- and kinetic parameters
yielding the smallest possible standard deviation between simulated and
experimental curves.
Key Features for Conducting Electrochemical Experiments using the
Reference 600 Modules
- Executing experiments with a Reference 600
potentiostat (GAMRY
Instruments) from within DigiElch 7 in a way that is perfectly consistent with doing the
simulations.
- The definition of scan segments used in the experiment is
accomplished using dialog elements which are identical or very similar to those
used for doing simulations.
- "Run & Fit" i.e. current curves (or impedance data)
measured in this way can be directly used for data fitting.
- One-click determination of uncompensated ohmic
resistance, Ru, by measuring the impedance in a potential range where the
faradaic current is negligible small.
- One-click "Measure IR-drop, Adjust IR-Compensation & Run
Experiment". That means:
- the uncompensated ohmic resistance, Ru, is measured as described above.
- the IR-Compensation is automatically adjusted using the greatest
possible value that is just a little bit smaller than the measure value of Ru.
- the experiment is started.
- Automatized approach for subtracting the experimental
background current from measured current curves.
- Export of the screen display in Windows enhanced meta
file (*.emf) format.
- Export of experimental current curves into ASCII-files.
Several formatting options which enable the exported data to be imported into
third-party presentation software.