Molecular Dynamics

MMD is a classical molecular dynamics code implemented as an App for Android. MMD is acronym for Method of Molecular Dynamics, which is a computer simulation of particles (atoms, molecules) motion. This simulation is done with respect to the given initial and boundary conditions and a potential that describes the particle interaction.

The trajectories of the particles are determined numerically. The well known Velocity Verlet integration of Newton's equation of motions is used for a system of interacting particles. Forces between particles are defined analytically using a "pair potential function" that depends on the distance between two particles.

In physics, MMD is used to examine the dynamics of atomic-level phenomena that cannot be observed directly. Within the mobile devices context, it can be used as a small mobile laboratory to understand the basics of the particle physics. Furthermore it can be used to produce nice dynamical pictures that are suitable as a live wallpaper.

Application features:

- The application can be set as a live wallpaper that visualizes the current experimental set up.
- In the live wallpaper mode, the active “static” wallpaper can be used as a background. You can mix your favorite background picture with particles “flying” in front of it.
- The changes made in main application will be applied to live wallpaper daemon to make the wallpaper tuning easier.
- Generation of an initial structure of the particles use diagonal or square grids with given dimension
- Possibility to select a boundary condition (full energy is constant, kinetic energy is constant, or no constraints)
- If kinetic energy is constrained, it is possible to apply “thermal change” that simulates heating/cooling of the system
- Possibility to change the gravity value. The gravity vector can be also changed by rotating of the device.
- Possibility to select and visualize selected potential. Currently, three common potentials are available: Lennard-Jones, Morse and Born-Mayer.
- The particle skin can be selected from build-in clip art.
- Multi-touch interface is used to zoom and drag the experimental area.

Note: since the application implements a numerical integration method, it generates a significant CPU load. Therefore, the live wallpaper mode is not suitable for low-power devices.

Keywords: live wallpaper, HD wallpaper, physics, molecular dynamics, atom simulations, experiment