SphericalTip

The SphericalTip potential models an AFM tip as a sphere. This is a simpler model compared to the SphericallyBluntedConicTip, but it can be sufficient for many applications and is computationally less expensive.

The potential includes: 1. Tip-sample interaction: A Lennard-Jones-like potential between the tip and sample particles. 2. Tip-chip interaction: A harmonic potential representing the cantilever.

This potential also includes features for simulating approach and retraction curves in AFM indentation experiments.

---

• type: AFM, SphericalTip

• parameters: * epsilon: real: Interaction strength parameter \([energy]\) * sigma: real: Interaction range parameter \([distance]\) * K: real: Vertical spring constant of the cantilever \([energy/distance^2]\) * Kxy: real: Lateral spring constant of the cantilever \([energy/distance^2]\) * tipVelocity: real: Velocity of the tip in the z-direction \([distance/time]\) * startChipPosition: real3: Initial position of the chip (cantilever base) \([distance]\) * indentationStartStep: ullint: Simulation step to start the indentation * indentationBackwardStep: ullint: Simulation step to start the retraction (optional)

Example:

"afmTip":{
  "type":["AFM","SphericalTip"],
  "parameters":{
    "epsilon": 100.0,
    "sigma": 0.1,
    "K": 10.0,
    "Kxy": 1.0,
    "tipVelocity": 0.1,
    "startChipPosition": [0.0, 0.0, 20.0],
    "indentationStartStep": 1000,
    "indentationBackwardStep": 10000
  }
}

Note

This potential allows for simulating complete AFM indentation cycles, including approach, contact, and retraction phases. The indentation process starts at indentationStartStep and reverses at indentationBackwardStep if specified.

Tip

If indentationBackwardStep is not specified or set to 0, the tip will continue to indent without retracting.

Warning

Ensure that indentationBackwardStep is larger than indentationStartStep if both are specified.