**Dynamics of nanoparticle adhesion**

JMY Carrillo and AV Dobrynin, JOURNAL OF CHEMICAL PHYSICS, 137, 214902 (2012).

DOI: 10.1063/1.4769389

We performed molecular dynamics simulations and theoretical analysis of
nanoparticle pulling off from adhesive substrates. Our theoretical model
of nanoparticle detachment is based on the Kramers' solution of the
stochastic barrier crossing in effective one-dimensional potential well.
The activation energy, Delta E, for nanoparticle detachment first
decreases linearly with increasing the magnitude of the applied force,
f, then it follows a power law Delta E proportional to (f* - f)(3/2) as
magnitude of the pulling force f approaches a critical detachment force
value, f*. These two different regimes in activation energy dependence
on magnitude of the applied force are confirmed by analyzing
nanoparticle detachment in effective one-dimensional potential obtained
by weighted histogram analysis method. Simulations show that detachment
of nanoparticle proceeds through neck formation such that magnitude of
the activation energy is determined by balancing surface energy of the
neck connecting particle to a substrate with elastic energy of
nanoparticle deformation. In this regime the activation energy at zero
applied force, Delta E-0, for nanoparticle with radius, R-p, shear
modulus, G, surface energy, gamma(p), and work of adhesion, W, is a
universal function of the dimensionless parameter delta proportional to
gamma W-p(-2/3)(GR(p))(-1/3). Simulation data are described by a scaling
function Delta E-0 proportional to gamma R-5/2(p)p(1/2)
G(-3/2)delta(-3.75). Molecular dynamics simulations of nanoparticle
detachment show that the Kramers' approach fails in the vicinity of the
critical detachment force f* where activation energy barrier becomes
smaller than the thermal energy k(B)T. In the interval of the pulling
forces f > f* nanoparticle detachment becomes a deterministic process.
(C) 2012 American Institute of Physics.
**http://dx.doi.org/10.1063/1.4769389**

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