A persistent challenge for multiscale methods is the time-scale limitation of molecular dynamics.
Nonequilibrium statistical mechanics provides a way forward, but so far has offered significant insight only for the simplest of molecular models (e.g., moderately rarified monatomic gases).  Instead of simplifying the model, one can keep the model intact ‚Äì use MD with accurate atomic forces ‚Äì but try to simplify the solution.  One way is to focus on near-equilibrium behavior in some sense and generalize results from equilibrium statistical mechanics.  Alternatively, Objective Molecular Dynamics (OMD) simplifies solutions by exploiting the group invariance of the equations of molecular dynamics.  In OMD only a modest number of atoms are simulated (typically, 50-1000) and the motions of the other, typically infinite, set of atoms (the non-simulated atoms) are given by the group action on the simulated atoms.  The basic theorem of OMD says that all the atoms satisfy MD for their forces.  

After briefly explaining the method, the main purpose of the lecture is to present briefly a variety of examples, all far-from-equilibrium, that illustrate unexpected ways of using OMD.  These include 1) simulations of compressible and incompressible gas flows, including cases of dissociation and of the spontaneous formation of droplets (phase change) induced by sudden expansion, 2) simulations of the bending torsion and failure of carbon nanotubes using helical groups, 3) simulations of frictional behavior of sliding surfaces.  Besides the work of the authors, the lecture draws on earlier work with Kaushik Dayal, Alessia Nota and Juan J. L. Velazquez.


Objective Molecular Dynamics for gas flows, carbon nanotubes, phase transformation, dissociation and friction

The Virtual Technical Meeting of the Society of Engineering Science 2020 is the first fully virtual meeting of the SES community to envision and connect during the hiatus created by Covid-19, providing a platform for the exchange of ideas, and to showcase the latest research in the field of engineering science.

[Visit the Programme](https://drive.google.com/file/d/1BoCPBzrr1IQFANuzQI8a-paXCJoOcCkB/view?usp=sharing) | [Visit the Prerecorded Video/Poster List](https://drive.google.com/file/d/1XHLeEXJxEFjCSsNScuLDfMwy1X7oy7oJ/view?usp=sharing) | [View the Session Grid](https://drive.google.com/file/d/1VeDOC-Ev5m_ymYjXnjaXSZHR3_DARiLt/view?usp=sharing)