Buckingham¶

Description¶

The buckingham_compute_force operator calculates the Buckingham (exp-6) pair potential given by

\[ E(r) = A \, e^{-r/\rho} - \frac{C}{r^{6}} \quad \text{for} \quad r<r_c \]

with \(r_c\) the cutoff and \((A,\rho,C)\) the potential parameters described in the following table.

Parameter	Units	Description
\(A\)	energy	Short-range repulsive amplitude
\(\rho\)	distance	Repulsive decay length
\(C\)	energy·distance\(^6\)	Dispersion (attractive) coefficient
\(r_c\)	distance	Cutoff radius

YAML syntax¶

buckingham_compute_force:
  rcut: VALUE UNITS
  parameters: { A: VALUE UNITS , rho: VALUE UNITS , C: 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
buckingham_compute_force:
  parameters: { A: 1000.0 eV , rho: 0.30 ang , C: 1200.0 eV*ang^6 }
  rcut: 8.0 ang

# Symetric variant
buckingham_compute_force_symetric:
  parameters: { A: 1000.0 eV , rho: 0.30 ang , C: 1200.0 eV*ang^6 }
  rcut: 8.0 ang

Systems with multiple atomic species

buckingham_multi_force:
  rcut: 8.0 ang
  common_parameters: { A: 0.0 , rho: 0.0 , C: 0.0 }
  parameters:
    - { type_a: O , type_b: O , rcut: 8.0 ang , parameters: { A: 9547.96 eV , rho: 0.21916 ang , C: 32.0 eV*ang^6 } }
    - { type_a: Si , type_b: O , rcut: 8.0 ang , parameters: { A: 18003.7572 eV , rho: 0.2052 ang , C: 133.5381 eV*ang^6 } }