OpenFF Units documentation

openff-units

to_openmm

openff.units.openmm.to_openmm(quantity: Quantity) → openmm_unit.Quantity

Convert an OpenFF Quantity to an OpenMM Quantity

openmm.unit.quantity.Quantity from OpenMM and openff.units.Quantity from this package both represent a numerical value with units. The units available in the two packages differ; when a unit is missing from the target package, the resulting quantity will be in base units (kg/m/s/A/K/mole), which are shared between both packages. This may cause the resulting value to be slightly different to the input due to the limited precision of floating point numbers.

Examples

>>> from openff.units import unit
>>> from openff.units.openmm import to_openmm
>>> from openmm import unit as openmm_unit
>>> length = unit.Quantity(9.0, unit.angstrom)
>>> to_openmm(length)
Quantity(value=9.0, unit=angstrom)
>>> assert isinstance(to_openmm(length), openmm_unit.Quantity)