SplitLennardJones

The SplitLennardJones potential is a modified version of the Lennard-Jones potential that uses different energy scales for the repulsive and attractive parts. This allows for more flexibility in tuning the interaction between particles.

\[\begin{split}U = \begin{cases} 4\epsilon_r \left[\left(\frac{\sigma}{r}\right)^{12} - \left(\frac{\sigma}{r}\right)^6\right] + (\epsilon_r - \epsilon_a) & \text{if } r < r_c \\ 4\epsilon_a \left[\left(\frac{\sigma}{r}\right)^{12} - \left(\frac{\sigma}{r}\right)^6\right] & \text{if } r_c \leq r < r_{\text{cutoff}} \end{cases}\end{split}\]

where:

• \(\epsilon_r\) is the repulsive energy scale

• \(\epsilon_a\) is the attractive energy scale

• \(\sigma\) is the distance at which the potential is zero

• \(r\) is the distance between particles

• \(r_c = 2^{1/6}\sigma\) is the cutoff distance between repulsive and attractive regimes

---

• type: NonBonded, SplitLennardJones

• parameters:

  • cutOffFactor: real: Interaction range as a multiple of sigma

  • epsilon_r: real: Repulsive energy scale \([energy]\)

  • epsilon_a: real: Attractive energy scale \([energy]\)

• data:

  • name_i: string: Type of particle i

  • name_j: string: Type of particle j

  • epsilon: real: Potential well depth \([energy]\)

  • sigma: real: Zero-potential distance \([distance]\)

Example:

"splitLJ":{
  "type":["NonBonded","SplitLennardJones"],
  "parameters":{
    "cutOffFactor":2.5,
    "epsilon_r":1.5,
    "epsilon_a":1.0,
    "condition":"all"
  },
  "labels":["name_i", "name_j", "epsilon", "sigma"],
  "data":[
    ["A", "A", 1.0, 1.0],
    ["A", "B", 1.2, 0.9],
    ["B", "B", 0.8, 1.1]
  ]
}

Tip

The SplitLennardJones potential allows for independent control of the repulsive and attractive parts of the interaction, which can be useful for modeling systems with complex interparticle interactions.

Note

For an explanation of how select the neighbors list (and the use of the condition parameter), see the common documentation for the non-bonded potentials.