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Issue 3, 2017
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Evaluating the friction of rotary joints in molecular machines

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A computationally-efficient method for evaluating friction in molecular rotary bearings is presented. This method estimates drag from fluctuations in molecular dynamics simulations via the fluctuation–dissipation theorem. This is effective even for simulation times short compared to a bearing's energy damping time and for rotation speeds comparable to or below typical thermal values. We apply this method to two molecular rotary bearings of similar size at 300 K: previously studied nested (9,9)/(14,14) double-walled carbon nanotubes and a hypothetical rotary joint consisting of single acetylenic bonds in a rigid diamondoid housing. The acetylenic joint has a rotational frictional drag coefficient of 2 × 10−35 kg m2 s−1. The friction for the nested nanotubes is 120 times larger, comparable to values reported by previous studies. This fluctuation-based method could evaluate dissipation in a variety of molecular systems with similarly rigid and symmetric bearings.

Graphical abstract: Evaluating the friction of rotary joints in molecular machines

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Publication details

The article was received on 23 Mar 2017, accepted on 16 May 2017 and first published on 16 May 2017

Article type: Paper
DOI: 10.1039/C7ME00021A
Mol. Syst. Des. Eng., 2017,2, 235-252

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    Evaluating the friction of rotary joints in molecular machines

    T. Hogg, M. S. Moses and D. G. Allis, Mol. Syst. Des. Eng., 2017, 2, 235
    DOI: 10.1039/C7ME00021A

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