Evans-Edwards model

Other computer simulations, such as the Evans Edwards model of a chain in an array of fixed obstacles (described in detail in Section 9.6.2) exhibit fluctuations of the tube length and also find stronger molar mass dependences of relaxation time t and diffusion coefficient... 

Evans-Edwards model of entangled chain dynamics... 

Evans-Edwards model on a two-dimensional square lattice. Corner flips (move 2) cross obstacles and are forbidden. End flips (move 1) and kink flips (move 3) satisfy topological constraints and are allowed. 

The limit in front of the ratio means that the time t has to be much longer than the longest relaxation time of the chain. The resulting diffusion coefficients obtained by Monte Carlo simulation of the Evans-Edwards model of entangled polymers are presented in Fig. 9.33(a). The diffusion coefficient decreases with the number of monomers in the chain. Another quantity that can be extracted from the Monte Carlo simulations of the Evans-Edwards model is the relaxation time of the chain. It can be defined as the characteristic decay time of the time correlation function of the end-to-end vector R[t)R 0)) exp( t/Trep). Figure 9.33(b) presents the results of such simulations. 

Chain length dependence of diffusion coefficient and relaxation time from Monte Carlo simulations of the Evans-Edwards model. Filled circles are from J. M. Deutsch and T. L. Madden,... 

Carlo simulations of the Evans-Edwards model. The fact that the results of the Evans-Edwards model that does not assume the existence of the tube agree with the results of the repton model validates the concept of the confining tube. 

Stone D, Evans MJ, Edwards PM, Commane R, Ingham T, Rickard AR, Brookes DM, Hopkins J, Leigh RJ, Lewis AC, Monks PS, Oram D, Reeves CE, Stewart D, Heard DE (2011) Isoprene oxidation mechanisms measurements and modelling of OH and HO(2) over a South-East Asian tropical rainforest during the OPS field campaign. Atmos Chem Phys 11 6749-6771... 

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