指数扩展格网络方法：模拟球、柱和旋转圆盘电极体系电化学问题的有效方法

An exponentially expanded space grid technique has been employed in the network simulation of chronoamperometric and voltammetric problems in spherical, cylindrical and rotating-disk electrode systems, leading to an effective simulation strategy for electrochemical problems: exponentially expanded grid network approach (EEGNA). The success of this method is largely due to the improved ability in processing the boundary singularities existing for non-planar diffusions and the enhanced simulation speed and accuracy in contrast to the uniform or quasi-uniform grid network approach.     

Universal Electrochemical／Chemical Simulator Based on an Exponentially Expanding Grid Network Approach

A universal simulator capable of simulating virtually any user-defined electrochemical/chemical problems in one-dimensional diffusion geometry was developed based on an exponentially expanding grid modification of the existing network approach. Some generalized reaction-diffusion governing equations of an arbitrary electrochemical/chemical process were derived, and program controlled automatic generation of the corresponding PSPICE netlist file was realized. On the basis of the above techniques, a universal simulator package was realized, which is capable of dealing with arbitrarily complex electrochemical/chemical problems with one-dimensional diffusion geometry such as planar diffusion, spherical diffusion, cylindrical diffusion and rotational disk diffusion-convection processes. The building of such a simulator is easy and thus it would be very convenient to have it updated for simulations of newly raised electrochemical problems.     

A strategy to improve the accuracy of digital simulation for electroanalytical chemistry

A strategy for digital simulation methods was presented for solving partial differential equations, called as IPBFP which is to insert M points before the first time point of the usual way, to decrease simulation errors. The theoretical analysis and simulation results show that it can improve the fully implicit method with any dimensionless diffusion coefficient A, Crank-Nicolson method with large and Saul'yev method with small . The IPBFP is convenient to arrange the simulation time points flexibly and reduce calculation time and errors. This approach can combine the merits of non-uniform time grid and uniform time grid methods in simulation for electrochemical studies.     

Single Alternating Group Explicit（SAGE） Method for Electrochemical Finite Difference Digital Simulation

The four different schemes of Group Explicit Method (GEM):GER,GEL,SAGE and DAGE have been claimed to be unstable when employed for electrochemical digital simulations with large model diffusion coefficient DM.However,in this investigation,in spite of the conditional stability of GER and GEL,the SAGE scheme,which is a combination of GEL and GER,was found to be unconditionally stable when used for simulations of electrochemical reaction-diffusion and had a performance comparable with or even better than the fast Quasi Explicit Finite Difference Method(FQEFD) in some aspects.Corresponding differential equations of SAGE scheme for digital simulations of various electrochemical mechanisms with both uniform and exponentially expanded space units were established.The effectiveness of the SAGE method was further demonstrated by the simulations of an EC and a catalytic mechanism with very large homogeneous rate constants.     

Studies on Hydrogen Bonding Network Structures of Konjac Glucomannan

In this paper, the hydrogen bonding network models of konjac glucomannan （KGM） are predicted in the approach of molecular dynamics （MD）. These models have been proved by experiments whose results are consistent with those from simulation. The results show that the hydrogen bonding network structures of KGM are stable and the key linking points of hydrogen bonding network are at the O（6） and O（2） positions on KGM ring. Moreover, acety has significant influence on hydrogen bonding network and hydrogen bonding network structures are more stable after deacetylation.     

Organic interfacial engineering of gold nanowires for selective glycerol electrooxidation

The selective electrochemical conversion of glycerol into value-added products is a green and sustainable strategy for the biomass utilization. In this work, Au nanowires(Au-NW) modified with polyethyleneimine(PEI) molecule(Au-NW@PEI) is obtained by an up-bottom post-modification approach.Physical characterization, molecular dynamics simulation and density functional theory demonstrate that the loose-packed PEI monolayer firmly and uniformly distribute on the Au-NW surface due to the strong Au-N...     

Polymer networks by molecular dynamics simulation: Formation, thermal, structural and mechanical properties

A molecular dynamics simulation method is presented and used in the study of the formation of polymer networks. We study the formation of networks representing the methylene repeating units as united atoms. The network formation is accomplished by cross-linking polymer chains with dedicated functional end groups. The simulations reveal that during the cross-linking process, initially branched molecules are formed before the gel point; approaching the gel point, larger branched entities are formed through integration of smaller branched molecules, and at the gel point a network spanning the simulation box is obtained; beyond the gel point the network continues to grow through the addition of the remaining molecules of the sol phase onto the gel (the network); the final completion of the reaction occurs by intra-network connection of dangling ends onto unsaturated cross-linkers. The conformational properties of the strands in the undeformed network are found to be very similar with the conformational properties of the chains before cross-linking. The uniaxial deformation of the formed networks is investigated and the modulus determined from the stress-strain curves shows reciprocal scaling with the precursor chain length for networks formed from sufficiently large precursor chains (N ≥ 20).     

Structures and Hydrogen Bonding Interactions in Urea-water System Studied by All-atom MD Simulation and Chemical Shifts in NMR Spectrum

The interactions and structures of the urea-water system are studied by an all-atom molecular dynamics （MD） simulation. The hydrogen-bonding network and the radial distribution functions are adopted in MD simulations. The structures of urea-water mixtures can be classified into different regions from the analysis of the hydrogen-bonding network. The urea molecule shows the certain tendency to the self-aggregate with the mole fraction of urea increasing. Moreover, the results of the MD simulations are also compare with the chemical shifts and viscosities of the urea aqueous solutions, and the statistical results of the average number hydrogen bonds in the MD simulations are in agreement with the experiment data such as chemical shifts of the hydrogen atom and viscosity.     

In situ NMR diffusion coefficients assessment of lithium ion conductor using electrochemical priors and Arrhenius constraint——A computational study

In situ NMR measurements of the diffusion coefficients,including an estimate of signal strength,of lithium ion conductor using diffusion-weighting pulse sequence are performed in this study.A cascade bilinear model is proposed to estimate the diffusion sensitivity factors of pulsed-field gradient using prior information of the electrochemical performance and Arrhenius constraint.The model postulates that the active lithium nuclei participating electrochemical reaction are relevant to the NMR signal intensity,when discharge rate or temperature condition is varying.The electrochemical data and the NMR signal strength show a highly fit with the proposed model according our simulation and experiments.Furthermore,the diffusion time is constrained by temperature based on Arrhenius equation of reaction rates dependence.An experimental calculation of Li_4Ti_5O_(12)(LTO)/carbon nanotubes(CNTs) with the electrolyte evaluating at 20 ℃ is presented,which the b factor is estimated by the discharge rate.     

Celestine blue as a new indicator in electrochemical DNA biosensors

Celestine blue(CB)was introduced as a new electroactive indicator in DNA biosensors.The interaction of CB with DNA was investigated by electrochemical and spectroscopic methods.The effect of buffer kind and p H on the electrochemical behavior of CB was studied.The peak currents of CB were linearly related to DNA concentration in the range of 5.0×10~(-9) to 1.0×10~(-7)mol/L.The detection limit of this approach was 4.76×10~(-10) mol/L.Based on spectrometry data a hypochromic effect was observed in UV-Vis spectra of CB with increasing DNA concentration.The results illustrate the possible interaction mode between CB and DNA is electrostatic binding.     

指数扩展的网络方法模拟超快循环伏安曲线

将指数扩展格原理用于网络模拟方法,给出了模拟受欧姆降歪曲的超快伏安曲线的电路网络模型,利用电路模拟软件ＰＳＰＩＣＥ给出该电路的瞬态响应曲线,并与数值解进行对比,结果表明这一模拟算法准确而稳定,而且计算速度比等格网络法提高１０倍以上。     

网络法数字模拟电活性物种吸附体系的循环伏安曲线

使用指数扩展的网络方法对电活性物质吸附与扩散共存的电化学体系进行了模拟,包括吸附为平衡和非平衡态的情形,所得结果跟文献报道一致并有所补充。该方法具有简便、直观、灵活性强等优点。     

Explicit finite-difference simulation of a dropping mercury electrode utilizing an exponentially expanded space grid

An exponentially expanded space grid has been applied in the explicit finite-difference computer simulation of a dropping mercury electrode (DME). The simulator has been proved to be considerably faster than previously described models using uniform grids (S.W. Feldberg, J. Electroanal. Chem., 109 (1980) 69) and easily adaptable to different electrode reaction stoichiometries and forms of excitation potential.     

Higher-order spatial discretisations in electrochemical digital simulations. Part 4. Discretisation on an arbitrarily spaced grid

A systematic approach to the construction of finite difference formulae for the approximation to first and second derivatives with respect to space on an arbitrarily spaced grid is presented. The finite difference formulae, combined with backward implicit (BI) and extrapolation methods, are used for electrochemical simulations and tested for efficiency. Excellent results are obtained with second and third order discretisations even for very small space intervals in the vicinity of the electrode and strongly expanding grid spacings. This ensures efficient simulation of kinetic-diffusion systems where, due to a fast homogeneous reaction, a thin reaction layer is formed adjacent to the electrode.     

A new strategy for simulation of electrochemical mechanisms involving acute reaction fronts in solution: Application to model mechanisms

The new strategy for adaptive simulation of electrochemical reaction mechanisms described in a previous paper (C. Amatore, O. Klymenko, I. Svir. Electrochem. Commun., (2010), doi:10.1016/j.elecom.2010.06.009) [1] provides an efficient method of obtaining accurate concentration distributions and electrochemical currents. In this paper, this strategy is illustrated and tested more deeply upon simulating several representative classical electrochemical mechanisms involving fast homogeneous comproportionation or disproportionation reactions that pose severe difficulties when simulated by classical finite difference methods including those based on exponentially expanding grids.     

Damping of Crank-Nicolson error oscillations

The Crank-Nicolson (CN) simulation method has an oscillatory response to sharp initial transients. The technique is convenient but the oscillations make it less popular. Several ways of damping the oscillations in two types of electrochemical computations are investigated. For a simple one-dimensional system with an initial singularity, subdivision of the first time interval into a number of equal subintervals (the Pearson method) works rather well, and so does division with exponentially increasing subintervals, where however an optimum expansion parameter must be found. This method can be computationally more expensive with some systems. The simple device of starting with one backward implicit (BI, or Laasonen) step does damp the oscillations, but not always sufficiently. For electrochemical microdisk simulations which are two-dimensional in space and using CN, the use of a first BI step is much more effective and is recommended. Division into subintervals is also effective, and again, both the Pearson method and exponentially increasing subintervals methods are effective here. Exponentially increasing subintervals are often considerably more expensive computationally. Expanding intervals over the whole simulation period, although capable of satisfactory results, for most systems will require more cpu time compared with subdivision of the first interval only.