Stability analysis of ultrathin lubricant films via surface energy measurements and molecular dynamics simulations

2005 ◽  
Vol 97 (10) ◽  
pp. 10P302 ◽  
Author(s):  
Qian Guo ◽  
Lei Li ◽  
Yiao-Tee Hsia ◽  
Myung S. Jhon
Keyword(s):  
Molecular Dynamics ◽  
Stability Analysis ◽  
Surface Energy ◽  
Molecular Dynamics Simulations ◽  
Lubricant Films ◽  
Dynamics Simulations

scholarly journals Surface energy of nanoparticles – influence of particle size and structure

2018 ◽  
Vol 9 ◽  
pp. 2265-2276 ◽  
Author(s):  
Dieter Vollath ◽  
Franz Dieter Fischer ◽  
David Holec
Keyword(s):  
Molecular Dynamics ◽  
Particle Size ◽  
Surface Energy ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Molecular Dynamics Simulations ◽  
Definition Of ◽  
Dynamics Simulations ◽  
Classical Thermodynamics ◽  
A Minor

The surface energy, particularly for nanoparticles, is one of the most important quantities in understanding the thermodynamics of particles. Therefore, it is astonishing that there is still great uncertainty about its value. The uncertainty increases if one questions its dependence on particle size. Different approaches, such as classical thermodynamics calculations, molecular dynamics simulations, and ab initio calculations, exist to predict this quantity. Generally, considerations based on classical thermodynamics lead to the prediction of decreasing values of the surface energy with decreasing particle size. This phenomenon is caused by the reduced number of next neighbors of surface atoms with decreasing particle size, a phenomenon that is partly compensated by the reduction of the binding energy between the atoms with decreasing particle size. Furthermore, this compensating effect may be expected by the formation of a disordered or quasi-liquid layer at the surface. The atomistic approach, based either on molecular dynamics simulations or ab initio calculations, generally leads to values with an opposite tendency. However, it is shown that this result is based on an insufficient definition of the particle size. A more realistic definition of the particle size is possible only by a detailed analysis of the electronic structure obtained from initio calculations. Except for minor variations caused by changes in the structure, only a minor dependence of the surface energy on the particle size is found. The main conclusion of this work is that surface energy values for the equivalent bulk materials should be used if detailed data for nanoparticles are not available.

Tunable Gigahertz Oscillators of Gliding Incommensurate Bilayer Graphene Sheets

2013 ◽  
Vol 80 (4) ◽  
Author(s):  
Ming Luo ◽  
Zhuhua Zhang ◽  
Boris I. Yakobson
Keyword(s):  
Molecular Dynamics ◽  
Surface Energy ◽  
Molecular Dynamics Simulations ◽  
Friction Force ◽  
Function Theory ◽  
Bilayer Graphene ◽  
Atomistic Simulations ◽  
Graphene Sheets ◽  
Dynamics Simulations ◽  
Oscillation Frequencies

Oscillators composed of incommensurate graphene sheets have been investigated by molecular dynamics simulations. The oscillation frequencies can reach tens of gigahertz range and depend on the surface energy of the bilayer graphene and the oscillatory amplitude. We demonstrate the tunability of such an oscillator in terms of frequency and friction by its varying geometric parameters. Exploration of the damping mechanism by combining the autocorrelation function theory and the direct atomistic simulations reveals that the friction force is proportional to the velocity of oscillatory motion. The results should help optimize the design of graphene-based nanoelectromechanical devices.

Sign in / Sign up

Export Citation Format

Share Document