# Berlin 2015 – wissenschaftliches Programm

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# CPP: Fachverband Chemische Physik und Polymerphysik

## CPP 21: Polymer dynamics

### CPP 21.2: Vortrag

### Dienstag, 17. März 2015, 09:45–10:00, C 264

**Numerical rate theory approach to polymer escape** — •Harri Mökkönen^{1,2}, Tapio Ala-Nissila^{1}, and Hannes Jónsson^{1,2} — ^{1}Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 1100, FIN-00076 Aalto, Espoo, Finland — ^{2}Faculty of Physical Sciences, University of Iceland, Reykjavik, Iceland

The polymer escape problem in an external double well potential is studied. The polymer is known to cross the energy barrier in a coiled form below critical length *N*_{C} and in a stretched form above *N*_{C}, corresponding to so called "kink" solution in instanton theory [1,2]. We perform Brownian dynamics simulations to obtain the crossing rate *R*_{MD} as a function of the chain length *N* and the spring constant *K*. We numerically find the minimum energy path of the transition and by using the harmonic approximation of transition state theory recover the crossing rate *R*_{HTST} agreeing with the simulations up to *N*_{C}. Above *N*_{C} the energy barrier of the transition becomes flat so the crossing rate by harmonic approximation fails to give the quantitatively correct rate. We study the diffusive mechanism on top of the flat barrier to obtain dynamical corrections *f*(*N*) for the harmonic approximation of the crossing rate *R*′ = *f*(*N*) *R*_{HTST}.

[1] S. K. Lee and W. Sung, *Phys. Rev. E* **63**, 021115 (2001).

[2] H. Mökkönen, T. Ikonen, H. Jonssón, T. Ala-Nissila, *J. Chem. Phys.* **140**, 054907 (2014).