Molecular dynamics study of the structure organization in a strongly coupled chain of charged particles
- Research and Information Center, National Institute for Fusion Science, Toki 509-52 (Japan)
- Department of Physics and Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
- Physics Department, University of California at Berkeley, Berkeley, California 94720 (United States)
The dynamical and equilibrium properties of a strongly coupled chain of charged particles (polyampholyte) submerged in an immobile viscous medium are studied using the molecular dynamics simulations. The polyampholyte relaxes to an equilibrium conformation typically in 300{omega}{sub pe}{sup {minus}1} due to folding of the chain for low temperatures, and expands several times faster for high temperatures, where {omega}{sub pe} is the plasma frequency. Three regimes with distinct conformations as stretched, oblate, and spherical are observed under the Coulomb force at high, medium, and low temperatures, respectively. The change in the conformations is considered to minimize the free energy through the electrostatic potential. The root-mean-squared size of the polyampholytes in these regimes is scaled, respectively, as R{sub g}{approximately}N{sup 1/2}, (NT){sup 1/3}, and N{sup 0.3}T{sup 0.8{minus}1.0}, where N is the number of monomers on the chain and T the temperature. The crossover point of the regimes is characterized by the unique values of the monomer distance 2R{sub g}/N{sup 1/3}, being insensitive to the length and stiffness of the chain. The present results agree well with the Flory theory in the high and medium temperature regimes. The densely packed state at low temperatures is first obtained here without the use of the lattice model. The transition among the different regimes under the Coulomb force is exactly reversible. However, the transition under the cooperation of the Coulomb force and the attractive short-range force exhibits a hysteresis against successive changes in temperature. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 544881
- Journal Information:
- Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 56, Issue 5; Other Information: PBD: Nov 1997
- Country of Publication:
- United States
- Language:
- English
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