from typing import Optional, Tuple
import unyt as u
from pydantic import ConfigDict, Field
from gmso.core.parametric_potential import ParametricPotential
from gmso.utils.expression import PotentialExpression
[docs]
class PairPotentialType(ParametricPotential):
"""A description of custom pairwise potential between 2 AtomTypes that does not follow combination rule.
This is a subclass of the gmso.core.ParametricPotential superclass.
PairPotentialType represents a type of pairwise potential between two
Atomtypes that does not follow a specific combination rule, and includes the functional
form describing its interactions. The functional form of the potential is
stored as a `sympy` expression and the parameters, with units, are stored
explicitly. The AtomTypes that are used to define the dihedral type are
stored as `member_types`.
Notes
-----
Inherits many functions from gmso.ParametricPotential:
__eq__, _validate functions
"""
member_types_: Optional[Tuple[str, str]] = Field(
None,
description="List-like of strs, referring to gmso.Atomtype.name or gmso.Atomtype.atomclass, "
"defining the members of this pair potential type",
alias="member_types",
)
model_config = ConfigDict(
alias_to_fields=dict(
**ParametricPotential.model_config["alias_to_fields"],
**{
"member_types": "member_types_",
},
),
)
def __init__(
self,
name="PairPotentialType",
expression=None,
parameters=None,
independent_variables=None,
potential_expression=None,
member_types=None,
tags=None,
):
super(PairPotentialType, self).__init__(
name=name,
expression=expression,
parameters=parameters,
independent_variables=independent_variables,
member_types=member_types,
potential_expression=potential_expression,
tags=tags,
)
@property
def member_types(self):
return self.__dict__.get("member_types_")
@staticmethod
def _default_potential_expr():
return PotentialExpression(
expression="4 * eps * ((sigma / r)**12 - (sigma / r)**6)",
independent_variables={"r"},
parameters={"eps": 1 * u.Unit("kJ / mol"), "sigma": 1 * u.nm},
)