Lennard-Jones¶

Description¶

The lj_compute_force operator calculates the standard 12/6 Lennard-Jones pair potential computes the given by

\[ E = 4 \epsilon \left[ \left(\frac{\sigma}{r}\right)^{12} - \left(\frac{\sigma}{r}\right)^{6} \right] \quad \text{for} \quad r<r_c \]

with \(r_c\), \(\epsilon\) and \(\sigma\) the potential parameters decribed in the following table.

Parameter	Units	Description
\(\varepsilon\)	energy	Depth of energy well
\(\sigma\)	distance	Distance of energy well from central particle
\(r_c\)	distance	Cutoff radius

YAML syntax¶

lj_compute_force:
  rcut: VALUE UNITS
  parameters: { epsilon: VALUE UNITS , sigma: VALUE UNITS }

VALUE = Physical value of the intended parameter.
UNITS = Units of the provided value that will be passed to the conversion helper for internal units conversion.

Usage examples¶

Systems with a single atomic specy

# Default variant
lj_compute_force:
  parameters: { epsilon: 0.0104 eV , sigma: 3.4 ang }
  rcut: 8.0 ang

# Symetric variant
lj_compute_force_symetric:
  parameters: { epsilon: 0.0104 eV , sigma: 3.4 ang }
  rcut: 8.0 ang

Systems with multiple atomic species

lj_multi_force:
  rcut: 8. ang
  common_parameters: { epsilon: 0.0 , sigma: 0.0 }
  parameters:
    - { type_a: Zn , type_b: Zn , rcut: 6.10 ang , parameters: { epsilon: 2.522E-20 J , sigma: 0.244E-09 m } }
    - { type_a: Cu , type_b: Zn , rcut: 5.89 ang , parameters: { epsilon: 4.853E-20 J , sigma: 0.236E-09 m } }