ESP [1] is a program to perform general electrochemical simulations and Best Fitting of experimental data. Some ideas (i.e. expanding space grid and Runge-Kutta integration) are inspired by Gosser's simulator CVSIM [2], who applied them into his simulator. Usually electrochemical simulators, i.e. like CVSIM [2], implement an "analog" waveform; ESP implement a "digital" one. It means that CV is performed by ESP as Staircase Voltammetry (SCV) rather than Cyclic Voltammetry (CV). Many electrochemists mistake analog for staircase CV. It is important to recognize that SCV and analog response are different. To my knowledge this is the first implementation of a digital-ramp simulator. With the large diffusion of digital potentiostat, like EG&G 273, SCV plays an important role with respect to analog potentiostat. Digital potential waveform allow the easy design of new techniques, as well as a less dependence of the shape of E/i plots from double layer capacitance, due to the exponential decay of the charging current. In the remaining part of this manual, CV term is used instead of the proper SCV. Available techniques in ESP are Cyclic Voltammetry (CV), Square Wave Voltammetry (SWV), Cronoamperometry (CA) and Sampled DC Polarography (SDC). This latter technique can be simulated either by solid electrode (constant area) or by dropping mercury electrode. The former can be supposed to be the simulation of a vibrating solid electrode, whereas the latter is simulated adopting the concept of a flat electrode moving towards the bulk of the solution which surface area (a sphere) increase by time [3]. ESP can simulate virtually any electrochemical mechanism, build as a combination of: a maximum of 20 species a maximum of 10 chemical reactions a maximum of 10 redox couple ESP perform diffusion by fast implementation (in C) of expanding space grid algorithm, to minimize computational time. Spatial grid double in size every fourth grid-increment [4]. Homogeneous chemical complications are solved by means of the Runge-Kutta integration of the fourth-order [5]. Best-Fitting routines for non-linear optimization are based on the Simplex technique [6]. COOL algorithm [7] is used; the experimental current i(exp) is expressed as a linear function of the dimensionless current function, i(sim): i(exp) = slope * i(sim) + intcp Here "slope" and "intcp" are constants that come from the linear regression between experimental and simulated current. Neither slope nor intcp depend by simulation parameters. If the ScaleFlag (SF) parameter is set to 0 then the output is that one of a pure simulation, e.g. slope=1 and intcp=0. Simulation input can be done by keyboard or by file. There are two kind of informations that ESP need to perform simulation: 1) a collection of experimental parameters (like scan rate, initial and final potentials, etc.), and 2) the mechanism you want to simulate. Both this informations are stored in the mechanism file, so that there is no necessity to re-type by keyboard every things. There are different files used by ESP, and every extension identify the kind of file. File organization follows: *.mec is an ASCII Mechanism file, where the mechanism is stored. This file is used for both direct simulation and Best Fitting. It can be written by any text editor or by the build-in mechanism editor. Its structure is self-explaining; see supplied examples. *.prn is an ASCII file. The first line must be: /* ASCII E i t */ or any permutation of {E, i, t}, i.e.: /* ASCII i E t */ (Capsare significative!). You can omit t (and type '-' instead of't'), but never omit E or i. Moreover, if t is omitted, the '-'must be the last, i.e.: /* ASCII E i - */ Each subsequent lineis a curve point; each point is made by two (t omitted) or three(t not omitted) values, and the order of the values must be inagreement with the order choosen in the first line. i.e.: /* ASCII E i - */ 0.010 1.234E-7 0.020 1.567E-7 ... END The last line of *.prn must be "END". The same file format is used by the output simulation file (P option). The main aim of *.prn file is to provide an alternative input/output file format which can be used by non-EG&G users. *.sim is the simulation output file. It has approximately the same structure of M270 binary file, so who use the EG&G software can read it as a normal experimental file. Reading *.sim by EG&G software a warning could appear: don't worry, you can continue. The best way to avoid trouble with *.sim files is to load them, skip the edventually warning message and immediately overwrite files without any further manipulations. This because I have no official information about the structure of M270 files: I just approximately analysed those files and tryed to reproduce them. *.sim can also be optimized like M270 file. *.fit is the Best Fit settings file (in binary). Store the whole VAR_OPT struct, wich include the experimental current as well as the value of parameters to be Fitted. It is possible to save *.fit an re-start the Best Fitting where you stopped it. *.??? is a M270 experimental file and can be Best Fitted. Each file which doesn't fit in above seen extensions, is supposed to be an M270 experimental file. You can run ESP as "ESP" alone (and you will be prompted to choose various possibilities) or you can type "ESP namefile" where the namefile extension reflect the kind of calculation you want. (i.e. ESP *.mec means simulation of the selected mechanism, ESP m270_file, ESP *.sim, ESP *.prn, ESP *.fit means Best Fitting).

ESP Electrochemical Simulation Package

NERVI, Carlo
1994-01-01

Abstract

ESP [1] is a program to perform general electrochemical simulations and Best Fitting of experimental data. Some ideas (i.e. expanding space grid and Runge-Kutta integration) are inspired by Gosser's simulator CVSIM [2], who applied them into his simulator. Usually electrochemical simulators, i.e. like CVSIM [2], implement an "analog" waveform; ESP implement a "digital" one. It means that CV is performed by ESP as Staircase Voltammetry (SCV) rather than Cyclic Voltammetry (CV). Many electrochemists mistake analog for staircase CV. It is important to recognize that SCV and analog response are different. To my knowledge this is the first implementation of a digital-ramp simulator. With the large diffusion of digital potentiostat, like EG&G 273, SCV plays an important role with respect to analog potentiostat. Digital potential waveform allow the easy design of new techniques, as well as a less dependence of the shape of E/i plots from double layer capacitance, due to the exponential decay of the charging current. In the remaining part of this manual, CV term is used instead of the proper SCV. Available techniques in ESP are Cyclic Voltammetry (CV), Square Wave Voltammetry (SWV), Cronoamperometry (CA) and Sampled DC Polarography (SDC). This latter technique can be simulated either by solid electrode (constant area) or by dropping mercury electrode. The former can be supposed to be the simulation of a vibrating solid electrode, whereas the latter is simulated adopting the concept of a flat electrode moving towards the bulk of the solution which surface area (a sphere) increase by time [3]. ESP can simulate virtually any electrochemical mechanism, build as a combination of: a maximum of 20 species a maximum of 10 chemical reactions a maximum of 10 redox couple ESP perform diffusion by fast implementation (in C) of expanding space grid algorithm, to minimize computational time. Spatial grid double in size every fourth grid-increment [4]. Homogeneous chemical complications are solved by means of the Runge-Kutta integration of the fourth-order [5]. Best-Fitting routines for non-linear optimization are based on the Simplex technique [6]. COOL algorithm [7] is used; the experimental current i(exp) is expressed as a linear function of the dimensionless current function, i(sim): i(exp) = slope * i(sim) + intcp Here "slope" and "intcp" are constants that come from the linear regression between experimental and simulated current. Neither slope nor intcp depend by simulation parameters. If the ScaleFlag (SF) parameter is set to 0 then the output is that one of a pure simulation, e.g. slope=1 and intcp=0. Simulation input can be done by keyboard or by file. There are two kind of informations that ESP need to perform simulation: 1) a collection of experimental parameters (like scan rate, initial and final potentials, etc.), and 2) the mechanism you want to simulate. Both this informations are stored in the mechanism file, so that there is no necessity to re-type by keyboard every things. There are different files used by ESP, and every extension identify the kind of file. File organization follows: *.mec is an ASCII Mechanism file, where the mechanism is stored. This file is used for both direct simulation and Best Fitting. It can be written by any text editor or by the build-in mechanism editor. Its structure is self-explaining; see supplied examples. *.prn is an ASCII file. The first line must be: /* ASCII E i t */ or any permutation of {E, i, t}, i.e.: /* ASCII i E t */ (Capsare significative!). You can omit t (and type '-' instead of't'), but never omit E or i. Moreover, if t is omitted, the '-'must be the last, i.e.: /* ASCII E i - */ Each subsequent lineis a curve point; each point is made by two (t omitted) or three(t not omitted) values, and the order of the values must be inagreement with the order choosen in the first line. i.e.: /* ASCII E i - */ 0.010 1.234E-7 0.020 1.567E-7 ... END The last line of *.prn must be "END". The same file format is used by the output simulation file (P option). The main aim of *.prn file is to provide an alternative input/output file format which can be used by non-EG&G users. *.sim is the simulation output file. It has approximately the same structure of M270 binary file, so who use the EG&G software can read it as a normal experimental file. Reading *.sim by EG&G software a warning could appear: don't worry, you can continue. The best way to avoid trouble with *.sim files is to load them, skip the edventually warning message and immediately overwrite files without any further manipulations. This because I have no official information about the structure of M270 files: I just approximately analysed those files and tryed to reproduce them. *.sim can also be optimized like M270 file. *.fit is the Best Fit settings file (in binary). Store the whole VAR_OPT struct, wich include the experimental current as well as the value of parameters to be Fitted. It is possible to save *.fit an re-start the Best Fitting where you stopped it. *.??? is a M270 experimental file and can be Best Fitted. Each file which doesn't fit in above seen extensions, is supposed to be an M270 experimental file. You can run ESP as "ESP" alone (and you will be prompted to choose various possibilities) or you can type "ESP namefile" where the namefile extension reflect the kind of calculation you want. (i.e. ESP *.mec means simulation of the selected mechanism, ESP m270_file, ESP *.sim, ESP *.prn, ESP *.fit means Best Fitting).
1994
2.4
Carlo Nervi
http://lem.ch.unito.it/chemistry/esp_manual.html
electrochemistry; digital simulation
Carlo Nervi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/45805
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