I read one paper Article Approach to failure in porous granular materials under compression
it referred to "using discrete element method to investigate the fracture of sedimentary rocks under uniaxial compression, focusing on how the system approaches macroscopic failure", however, they utilised the molecular dynamics simulations to generate the ballistic motion of particles of mass. Therefore, my question is "What's the difference between discrete element method and molecular dynamics method and the relationships between them?"
The primary difference is that in DEM the analyzed discrete particles have a shape, size (i.e. radius for spheres) and rotational degrees of freedom , in contrast to MD where you usually consider mass points in your analysis. Hence, other interactions between particles can be analyzed i.e. rotation, contact plasticity, friction.
MD is used in modeling in atomic scale (atoms or molecules).
DEM is used in larger scale: mostly in modeling of discontinuous materials (powders, rocks, granular).
"For simplicity, during the sedimentation process no tangential component of the contact force was considered"
That is probably the reason why the authors called the methodology for simulation of the ballistic motion MD. I would name it DEM.
Both DEM and MD are meant to model the discrete nature of particles. Although DEM is very closely related to molecular dynamics, the method is generally distinguished by its inclusion of rotational degrees-of-freedom as well as stateful contact and often complicated geometries. The most significant difference between the discrete element method and molecular dynamics is the consideration of the interparticle contact forces in the model. Molecular Dynamics can also be seen as a subset of Discrete Element Methods
Frankly:
DEM can be used to investigate the mechanical behavior and properties (also can be coupled with other analysis and simulation methods through packages like PFC, EDEM, etc).
While MD, concerns about the physio-chemical interactions between the molecules and often coupled with (Monte Carlo - MC, or Molecular Mechanics - MM) simulations through packages like Material Studio and alike.
Best of Luck,
Hamzah
Hi Zhaoyang,
Both DEM and Molecular dynamics are particle methods that determine trajectories of particles using Newton's equations of motion. In general, Discrete Element Method considers contact forces between interacting particles while in Molecular Dynamics, the forces are calculated using interatomic potentials. As a result, DEM is widely used in granular flow applications such as soil or powder mechanics.
The following handbook by Prof. Konietzky and Dr. Jakob might give you a brief idea on different particle methods:
https://tu-freiberg.de/fakult3/gt/feme/studium/Handbook_Particle_Methods.pdf
Cheers,
Gowthaman
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