**Molecular dynamics calculation of rotational diffusion coefficient of a
carbon nanotube in fluid**

BY Cao and RY Dong, JOURNAL OF CHEMICAL PHYSICS, 140, 034703 (2014).

DOI: 10.1063/1.4861661

Rotational diffusion processes are correlated with nanoparticle
visualization and manipulation techniques, widely used in
nanocomposites, nanofluids, bioscience, and so on. However, a
systematical methodology of deriving this diffusivity is still lacking.
In the current work, three molecular dynamics (MD) schemes, including
equilibrium (Green-Kubo formula and Einstein relation) and
nonequilibrium (Einstein-Smoluchowski relation) methods, are developed
to calculate the rotational diffusion coefficient, taking a single rigid
carbon nanotube in fluid argon as a case. We can conclude that the three
methods produce same results on the basis of plenty of data with
variation of the calculation parameters (tube length, diameter, fluid
temperature, density, and viscosity), indicative of the validity and
accuracy of the MD simulations. However, these results have a non-
negligible deviation from the theoretical predictions of Tirado et al.
**J. Chem. Phys. 81, 2047 (1984)**, which may come from several unrevealed
factors of the theory. The three MD methods proposed in this paper can
also be applied to other situations of calculating rotational diffusion
coefficient. (C) 2014 AIP Publishing LLC.

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