Dynamics of rigid and flexible constraints for polymers. Effect of the Fixman potential

Autor:	Dennis Perchak, Jeffrey Skolnick, Robert Yaris
Rok vydání:	1985
Předmět:	Physics chemistry.chemical_classification Valence (chemistry) Polymers and Plastics Organic Chemistry Autocorrelation Polymer Statistical mechanics Dihedral angle Inorganic Chemistry Bond length Classical mechanics chemistry Materials Chemistry Brownian dynamics Molecule
Zdroj:	Macromolecules. 18:519-525
ISSN:	1520-5835 0024-9297
DOI:	10.1021/ma00145a036
Popis:	Models of polymers can generally be divided into two classes: (a) flexible, wherein bond lengths and valence angles are constrained to nearly constant values by strong, harmonic potentials, and (b) rigid, wherein the constrainb are geometric, Le., fixed bond lengths and angles. In general, the statistical mechanics of such systems differ. By introduction of a compensating potential based on the metric determinant of the unconstrained coordinates (the Fixman potential), the rigid model can be made to reproduce the equilibrium flexible results. It is not clear whether the corresponding dynamics are also reproduced. The purpose of the present work is to investigate the effect of the Fixman potential on dynamics. We have performed Brownian dynamics simulations of three models of a n-butane-like molecule: flexible, rigid, and rigid-plus-Fixman potential. Results show that for certain autocorrelation functions of the dihedral angle, there is a definite, though small, difference in dynamics between the rigid and flexible models in the low-friction limit. At high friction the difference has decreased and the dynamics are essentially the same. The effect of the Fixman potential is minimal in both cases.
Databáze:	OpenAIRE
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