Lennard-Jones potential kernel

class mdk::LennardJones

Standard Lennard-Jones potential.

Public Functions

LennardJones() = default
inline LennardJones(double r_min, double depth)
inline double cutoff() const

The cutoff distance for the L-J potential. I’m not sure what is the “industry standard” cutoff but at 2.5 sigma the value of the potential is -0.016 epsilon, which seems fine as a cutoff. For comparison, at 2 sigma the value is -0.06225 epsilon which seems too high to cut off.

Returns

The cutoff distance.

inline void computeV(double norm, double &V, double &dV_dn) const

Compute the potential energy of the force field.

Parameters
  • norm – Distance between the residues.

  • V – Variable to add the potential to.

  • dV_dn – Variable to add the derivative to.

template<typename T1, typename T2>
inline void computeF(VRef unit, double norm, double &V, T1 F1, T2 F2) const

Compute and add the L-J force between two residues. The templates are here in order for us to be able to pass Eigen expressions to it.

Template Parameters
  • T1 – Type of an lvalue to add the force on the first residue to.

  • T2 – Type of an lvalue to add the force on the second residue to.

Parameters
  • unit – Normalized vector between the residues.

  • norm – Distance between the residues.

  • V – Variable to add the potential to.

  • F1 – Lvalue to add the force on the first residue to.

  • F2 – Lvalue to add the force on the second residue to.

Public Members

double r_min = 5.0 * angstrom
double depth = 1.0 * eps