Coulomb (Wolf)¶

Description¶

The coul_wolf_compute_force operator calculates the damped, shifted Coulomb (Wolf) pair potential:

\[ E(r) = \frac{1}{4\pi \varepsilon_0} \, q_i q_j \left[\frac{\operatorname{erfc}(\alpha r)}{r} - \frac{\operatorname{erfc}(\alpha r_c)}{r_c}\right] \quad \text{for} \quad r<r_c \]

with damping parameter \(\alpha\) and cutoff \(r_c\). The constant term ensures \(E(r_c)=0\). The force is also shifted to vanish at \(r_c\). The charges are the species charges.

The self energy of each particle is not included: add the coulombic_wolf_self operator with per_atom_charge: false. For per-atom charges, use coulombic_wolf. Both are described in Short range electrostatics.

Note

This style was named coul_wolf_pair before. The old operator names (coul_wolf_pair_compute_force...) and the potential name in compute_force_pair_multimat are still accepted, with a deprecation warning.

Parameter	Units	Description
`alpha`	1/distance	Wolf damping parameter \(\alpha\)
`rc`	distance	Cutoff radius \(r_c\) of the Wolf sum (use the same value as `rcut`)
`rcut`	distance	Cutoff radius of the pair potential

YAML syntax¶

coul_wolf_compute_force:
  rcut: VALUE UNITS
  parameters: { alpha: VALUE UNITS^-1 , rc: 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
coul_wolf_compute_force:
  parameters: { alpha: 0.20 ang^-1 , rc: 10.0 ang }
  rcut: 10.0 ang

# Symetric variant
coul_wolf_compute_force_symetric:
  parameters: { alpha: 0.20 ang^-1 , rc: 10.0 ang }
  rcut: 10.0 ang

# Self energy (thermodynamic output only)
coulombic_wolf_self:
  parameters: { alpha: 0.20 ang^-1 , rc: 10.0 ang }
  per_atom_charge: false

Systems with multiple atomic species

coul_wolf_multi_force:
  rcut: 10.0 ang
  common_parameters: { alpha: 0.20 ang^-1 , rc: 10.0 ang }
  parameters:
    - { type_a: Na , type_b: Cl , rcut: 10.0 ang , parameters: { } }
    - { type_a: Na , type_b: Na , rcut: 10.0 ang , parameters: { } }