Coulomb (Wolf)¶

Description¶

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

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

with damping parameter \(\alpha\) and cutoff \(r_c\). The constant term ensures \(E(r_c)=0\).

Parameter	Units	Description
\(\alpha\)	1/distance	Wolf damping parameter
\(\varepsilon_r\)	—	Relative dielectric constant of medium
\(r_c\)	distance	Cutoff radius

YAML syntax¶

coul_wolf_compute_force:
  rcut: VALUE UNITS
  parameters: { alpha: VALUE UNITS^-1 , epsilon_r: VALUE }

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 , epsilon_r: 1.0 }
  rcut: 10.0 ang

# Symetric variant
coul_wolf_compute_force_symetric:
  parameters: { alpha: 0.20 ang^-1 , epsilon_r: 1.0 }
  rcut: 10.0 ang

Systems with multiple atomic species

coul_wolf_multi_force:
  rcut: 10.0 ang
  common_parameters: { alpha: 0.20 ang^-1 , epsilon_r: 1.0 }
  parameters:
    - { type_a: Na , type_b: Cl , rcut: 10.0 ang , parameters: { } }
    - { type_a: Na , type_b: Na , rcut: 10.0 ang , parameters: { } }