Harmonic improper¶

Description¶

The harm_improper type of improper torsion potential calculates the standard harmonic improper torsion potential given by

\[ E = \frac{1}{2} k \left ( \chi -\chi_0 \right )^2 \]

with \(k\) and \(\phi_0\) the potential parameters decribed in the following table.

Parameter	Units	Description
\(k\)	energy	force constant
\(\phi_0\)	angle	equilibrium improper angle

YAML syntax¶

compute_force_improper:
  potentials_for_impropers:
    - types: [STRING, STRING, STRING, STRING]
      potential: harm_improper
      parameters:
        phi0: VALUE UNITS
        k: VALUE UNITS

STRING = Name of the atom type (specie) involved in the bending angle.
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 atom type (specie)

compute_force_improper:
  potentials_for_impropers:
    - types: [CA, CA, CA, CT]
      potential: harm_improper
      parameters:
        phi0: 0.0 degree
        k: 8.0e-19 J

Systems with several atom types (species)

compute_force_improper:
  potentials_for_impropers:
    - types: [CA, CA, CA, CT]
      potential: harm_improper
      parameters:
        phi0: 0.0 degree
        k: 8.0e-19 J
    - types: [CA, CA, CA, H]
      potential: harm_improper
      parameters:
        phi0: 0.0 degree
        k: 8.0e-19 J