scholarly journals Relative entropy of freely cooling granular gases. A molecular dynamics study

2021 ◽  
Vol 249 ◽  
pp. 04006
Author(s):  
Alberto Megías ◽  
Andrés Santos
Keyword(s):  
Molecular Dynamics ◽  
Relative Entropy ◽  
Velocity Distribution Function ◽  
Reference Distribution ◽  
Elastic Collisions ◽  
Velocity Inversion ◽  
Granular Gas ◽  
Maxwell Demon ◽  
Nonequilibrium Entropy ◽  
Molecular Dynamics Results

Whereas the original Boltzmann’s H-theorem applies to elastic collisions, its rigorous generalization to the inelastic case is still lacking. Nonetheless, it has been conjectured in the literature that the relative entropy of the velocity distribution function with respect to the homogeneous cooling state (HCS) represents an adequate nonequilibrium entropy-like functional for an isolated freely cooling granular gas. In this work, we present molecular dynamics results reinforcing this conjecture and rejecting the choice of the Maxwellian over the HCS as a reference distribution. These results are qualitatively predicted by a simplified theoretical toy model. Additionally, a Maxwell-demon-like velocity-inversion simulation experiment highlights the microscopic irreversibility of the granular gas dynamics, monitored by the relative entropy, where a short “anti-kinetic” transient regime appears for nearly elastic collisions only.

Determination of the Stress Distribution at the Interface Metal-Oxide: Numerical and Theoretical Considerations

2005 ◽  
Vol 237-240 ◽  
pp. 145-150 ◽  
Author(s):  
Sébastien Garruchet ◽  
A. Hasnaoui ◽  
Olivier Politano ◽  
Tony Montesin ◽  
J. Marcos Salazar ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Stress Distribution ◽  
Oxide Film ◽  
Metal Oxide ◽  
Reaction Kinetics ◽  
Analytical Model ◽  
Equilibrium Thermodynamics ◽  
Theoretical Considerations ◽  
Molecular Dynamics Results

In this paper we give a brief presentation of the approaches we have recently developed on the oxidation of metals. Firstly, we present an analytical model based on non-equilibrium thermodynamics to describe the reaction kinetics present during the oxidation of a metal. Secondly, we present the molecular dynamics results obtained with a code specially tailored to study the oxidation and growth of an oxide film of aluminium. Our simulations present an excellent agreement with experimental results.

Design and Modeling of a Peptide Based NanoTweezer

2006 ◽  
Author(s):  
Gaurav Sharma ◽  
Kaushal Rege ◽  
Constantinos Mavroidis ◽  
Martin L. Yarmush
Keyword(s):  
Molecular Dynamics ◽  
Coiled Coil ◽  
Computational Results ◽  
Actuation Mechanism ◽  
Electrostatic Charges ◽  
Environmentally Responsive ◽  
Force Profile ◽  
Potential Applications ◽  
Polypeptide Chains ◽  
Molecular Dynamics Results

The design hypothesis, architectures, and preliminary computational results of a peptide based nanoTweezer are presented in this paper. We engineered the α-helical coiled coil portion of the yeast transcriptional activator peptide called GCN4 to obtain an environmentally-responsive nanoTweezer. The dimeric coiled coil peptide consists of two identical ~4.5 nm long and ~3 nm wide polypeptide chains. The actuation mechanism depends on the modifying electrostatic charges along the peptide by varying the pH of the solution resulting in the reversible movement of helices and therefore, creating the motion of the tweezer. Preliminary molecular dynamics results indicated that pH changes led to a reversible deflection of 1–2 nm with the nanoTweezer. The force profile of the nanoTweezer motion and some potential applications are also discussed.

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