Calculation of Noncontact Forces between Silica Nanospheres

Abstract

Quantification of the interactions between nanoparticles is important in understanding their dynamic behaviors and many related phenomena. In this study, molecular dynamics simulation is used to calculate the interaction potentials (i.e., van der Waals attraction, Born repulsion, and electrostatic interaction) between two silica nanospheres of equal radius in the range of 0.975 to 5.137 nm. The results are compared with those obtained from the conventional Hamaker approach, leading to the development of modified formulas to calculate the van der Waals attraction and Born repulsion between nanospheres, respectively. Moreover, Coulomb's law is found to be valid for calculating the electrostatic potential between nanospheres. The developed formulas should be useful in the study of the dynamic behaviors of nanoparticle systems under different conditions.

Interaction forces between carbon nanospheres: A molecular dynamics simulation study

“…rms is about 0.62 70.04 Å, δ is about 1.60 70.10 Å, and δ Max is about 3.867 1.10 Å. However, for amorphous carbon nanospheres, there are always some surface atoms fluctuating out of the range of R 0 , i.e., δ Max þ R core 4 R 0 , similar to the case as α-quartz silica nanospheres (Sun et al, 2013a). According to Eq.…”

“…Details can be found in our previous studies. For brevity, the major simulation procedures are as follows (Sun et al, 2013a(Sun et al, , 2013b:…”

“…The interaction potential energies and their individual potential contributions (e.g., vdW attraction, Born repulsion) can be calculated in a similar way as done before (Sun et al, 2013a(Sun et al, , 2013b. Then, the corresponding interaction forces can be obtained by differentiating the interparticle potentials with respect to surface separation (d).…”

“…Therefore, the structure of diamond and amorphous carbon nanospheres will be characterized in a similar way as silica nanospheres (Sun et al, 2013a). All atoms with saturated coordination number are reflected as the "core" of a nanosphere.…”

“…On the other hand, it is known that the continuum models, developed at the macroscale (Feke et al, 1984;Hamaker, 1937;Johnson, 1985), cannot generally apply to nanoparticles due to the neglect of discrete atomic structure and surface effects (Bishop et al, 2009;Girifalco et al, 2000;Luan and Robbins, 2005). Recently, molecular dynamics (MD) simulation has been developed to calculate the interaction forces between α-quartz silica nanospheres, including the van der Waals (vdW) attraction, Born repulsion and mechanical contact forces during a normal impact (Sun et al, 2013a(Sun et al, , 2013bZeng et al, 2010). Such MD studies can help clarify a series of fundamental issues from atomic level.…”