# LigParGenForceFieldSource — OpenFF Evaluator documentation

# LigParGenForceFieldSource

class `openff.evaluator.forcefield.``LigParGenForceFieldSource`(preferred_charge_model=<ChargeModel.CM1A_1_14_LBCC: '1.14*CM1A-LBCC'>, cutoff=<Quantity(9.0, 'angstrom')>, request_url='', download_url='')

  A wrapper and the OPLSAAM force field which can be applied via the LigParGen server.

  References

  [1] Potential energy functions for atomic-level simulations of water and organic and

    biomolecular systems. Jorgensen, W. L.; Tirado-Rives, J. Proc. Nat. Acad. Sci. USA 2005, 102, 6665-6670

  [2] 1.14*CM1A-LBCC: Localized Bond-Charge Corrected CM1A Charges for Condensed-Phase

    Simulations. Dodda, L. S.; Vilseck, J. Z.; Tirado-Rives, J.; Jorgensen, W. L. J. Phys. Chem. B, 2017, 121 (15), pp 3864-3870

  [3] LigParGen web server: An automatic OPLS-AA parameter generator for organic ligands.

    Dodda, L. S.;Cabeza de Vaca, I.; Tirado-Rives, J.; Jorgensen, W. L. Nucleic Acids Research, Volume 45, Issue W1, 3 July 2017, Pages W331-W336

  `__init__`(preferred_charge_model=<ChargeModel.CM1A_1_14_LBCC: '1.14*CM1A-LBCC'>, cutoff=<Quantity(9.0, 'angstrom')>, request_url='', download_url='')

    Constructs a new LigParGenForceFieldSource object

    Parameters

      - preferred_charge_model (ChargeModel) – The preferred charge model to apply. In some cases the preferred charge model may not be applicable (e.g. 1.14*CM1A-LBCC may only be applied to neutral molecules) and so another model may be applied in its place.

      - cutoff (pint.Quantity) – The non-bonded interaction cutoff.

      - request_url (str) – The URL of the LIGPARGEN server file to send the parametrization to request to.

      - download_url (str) – The URL of the LIGPARGEN server file to download the results of a request from.

  Methods

  `__init__`([preferred_charge_model, cutoff, …]) | Constructs a new LigParGenForceFieldSource object
  `from_json`(file_path) | Create this object from a JSON file.
  `json`([file_path, format]) | Creates a JSON representation of this class.
  `parse_json`(string_contents[, encoding]) | Parses a typed json string into the corresponding class structure.

  Attributes

  `cutoff` | The non-bonded interaction cutoff.
  `download_url` | The URL of the LIGPARGEN server file to download the results of a request from.
  `preferred_charge_model` | The preferred charge model to apply.
  `request_url` | The URL of the LIGPARGEN server file to send the parametrization to request to.

  class `ChargeModel`(value)

    An enumeration.

  property `preferred_charge_model`

    The preferred charge model to apply. In some cases the preferred charge model may not be applicable (e.g. 1.14*CM1A-LBCC may only be applied to neutral molecules) and so another model may be applied in its place.

    Type

      ChargeModel

  property `cutoff`

    The non-bonded interaction cutoff.

    Type

      pint.Quantity

  property `request_url`

    The URL of the LIGPARGEN server file to send the parametrization to request to.

    Type

      str

  property `download_url`

    The URL of the LIGPARGEN server file to download the results of a request from.

    Type

      str

  classmethod `from_json`(file_path)

    Create this object from a JSON file.

    Parameters

      file_path (str) – The path to load the JSON from.

    Returns

      The parsed class.

    Return type

      cls

  `json`(file_path=None, format=False)

    Creates a JSON representation of this class.

    Parameters

      - file_path (str , optional) – The (optional) file path to save the JSON file to.

      - format (bool) – Whether to format the JSON or not.

    Returns

      The JSON representation of this class.

    Return type

      str

  classmethod `parse_json`(string_contents, encoding='utf8')

    Parses a typed json string into the corresponding class structure.

    Parameters

      - string_contents (str or bytes) – The typed json string.

      - encoding (str) – The encoding of the string_contents.

    Returns

      The parsed class.

    Return type

      Any