FixedHarmonicAnisotropicCenterOfMass

The FixedHarmonicAnisotropicCenterOfMass potential applies an anisotropic harmonic restraint to the center of mass of a set of particles, tethering it to a fixed point in space.

\[U = \frac{1}{2}K_x(x-x_0)^2 + \frac{1}{2}K_y(y-y_0)^2 + \frac{1}{2}K_z(z-z_0)^2\]

where:

• \(K_x, K_y, K_z\) are the spring constants in each direction

• \(x, y, z\) are the coordinates of the center of mass

• \(x_0, y_0, z_0\) are the coordinates of the fixed point

---

• type: Set1, FixedHarmonicAnisotropicCenterOfMass

• parameters: None

• data: * idSet_i: int: Identifier for the set of particles * K: real3: Spring constants in x, y, and z directions \([energy/distance^2]\) * r0: real3: Equilibrium position \([distance]\) * position: real3: Fixed point coordinates \([distance]\)

Example:

"fixedHarmonicAnisotropic":{
  "type":["Set1","FixedHarmonicAnisotropicCenterOfMass"],
  "labels":["idSet_i", "K", "r0", "position"],
  "data":[
    [0, [100.0, 100.0, 100.0], [0.0, 0.0, 0.0], [5.0, 5.0, 5.0]]
  ]
}

Note

This potential is useful for creating flexible tethers or anchors for groups of particles, allowing anisotropic behavior in different directions.