Plates

The Plates potential confines particles between two parallel plates, applying repulsive forces when particles approach the plates.

The initial separation between the plates is set by the platesSeparation parameter. The separation can be changed during the simulation by setting the compressionVelocity parameter to a non-zero value. If compressionVelocity is positive, the plates will move towards each other at the specified rate, if negative, they will move apart. The minimum and maximum allowed plate separations can be set using the minPlatesSeparation and maxPlatesSeparation parameters, respectively.

The potential uses a steep repulsive interaction (r^12) for each plate:

\[U(z) = \epsilon \left[\left(\frac{\sigma}{z - z_{\text{bottom}}}\right)^{12} + \left(\frac{\sigma}{z_{\text{top}} - z}\right)^{12}\right]\]

where \(z\) is the z-coordinate of the particle, \(z_{\text{bottom}}\) and \(z_{\text{top}}\) are the positions of the bottom and top plates, \(\epsilon\) is the energy scale, and \(\sigma\) is the length scale of the interaction.

  • type: External, Plates

  • parameters:

    • platesSeparation: real: Initial separation between the plates \([distance]\)

    • platesEpsilon: real: Energy scale of the repulsive interaction \([energy]\) (default: 1.0)

    • platesSigma: real: Length scale of the repulsive interaction \([distance]\) (default: 1.0)

    • compressionVelocity: real: Rate of change of the plate separation \([distance/time]\) (default: 0.0)

    • minPlatesSeparation: real: Minimum allowed plate separation \([distance]\) (default: 0.0)

    • maxPlatesSeparation: real: Maximum allowed plate separation \([distance]\) (default: infinity)

Example:

"plates":{
  "type":["External","Plates"],
  "parameters":{
    "platesSeparation": 20.0,
    "platesEpsilon": 1.0,
    "platesSigma": 1.0,
    "compressionVelocity": 0.01,
    "minPlatesSeparation": 10.0,
    "maxPlatesSeparation": 30.0
  }
}

Warning

Ensure that the initial configuration of particles is between the plates to avoid extremely large forces at the start of the simulation.

Tip

This potential is useful for simulating confined systems or studying the behavior of materials under compression.