Eur. Phys. J. E (2018) 41: 38
https://doi.org/10.1140/epje/i2018-11646-3

Regular Article

On the calculation of the potential of mean force between atomistic nanoparticles

¹ Dipartimento di Chimica e Biologia, Università di Salerno, Via Giovanni Paolo II 132, I-84084, Fisciano (SA), Italy
² Department of Chemical Science, Federico II University of Naples, via Cinthia, Complesso Monte S. Angelo, 80126, Napoli, Italy
³ Department of Organic Materials Science, University of Yamagata, 4-3-16 Jonan Yonezawa, 992-8510, Yamagata-ken, Japan

^* e-mail: gmunao@unisa.it

Received: 1 February 2018
Accepted: 7 March 2018
Published online: 27 March 2018

Abstract

We study the potential of mean force (PMF) between atomistic silica and gold nanoparticles in the vacuum by using molecular dynamics simulations. Such an investigation is devised in order to fully characterize the effective interactions between atomistic nanoparticles, a crucial step to describe the PMF in high-density coarse-grained polymer nanocomposites. In our study, we first investigate the behavior of silica nanoparticles, considering cases corresponding to different particle sizes and assessing results against an analytic theory developed by Hamaker for a system of Lennard-Jones interacting particles (H.C. Hamaker, Physica A 4, 1058 (1937)). Once validated the procedure, we calculate effective interactions between gold nanoparticles, which are considered both bare and coated with polyethylene chains, in order to investigate the effects of the grafting density on the PMF. Upon performing atomistic molecular dynamics simulations, it turns out that silica nanoparticles experience similar interactions regardless of the particle size, the most remarkable difference being a peak in the PMF due to surface interactions, clearly apparent for the larger size. As for bare gold nanoparticles, they are slightly interacting, the strength of the effective force increasing for the coated cases. The profile of the resulting PMF resembles a Lennard-Jones potential for intermediate , becoming progressively more repulsive for high and low interparticle separations.