ParabolaSurface

The ParabolaSurface potential models the interaction between particles and a planar surface using a parabolic potential. It acts only in the z-direction and is one-sided, applying a force only when particles are below the surface.

\[\begin{split}U(z) = \begin{cases} \frac{1}{2}\epsilon(z - z_s)^2, & \text{if } z \leq z_s \\ 0, & \text{if } z > z_s \end{cases}\end{split}\]

where:

• \(\epsilon\) is the strength of the potential

• \(z_s\) is the position of the surface

• \(z\) is the z-coordinate of the particle

---

• type: Surface, ParabolaSurface

• parameters:

  • surfacePosition: real: Position of the surface (z_s) \([distance]\)

• data:

  • name: string: Name of the particle type

  • epsilon: real: Strength of the potential \([energy/distance^2]\)

  • sigma: real: Not used, can be set to any value

Example:

"parabolaSurface":{
  "type":["Surface","ParabolaSurface"],
  "parameters":{
    "surfacePosition": 0.0
  },
  "labels":["name", "epsilon", "sigma"],
  "data":[
    ["A", 10.0, 1.0],
    ["B", 5.0, 1.0]
  ]
}

Note

The ParabolaSurface potential only applies forces in the z-direction and only when particles are below the surface (z ≤ z_s). It does not affect particles above the surface.

Tip

This potential can be used to create a soft, one-sided wall or to model interactions with a planar surface where the repulsion increases quadratically with distance.