Second virial coefficient
=========================

The *second virial coefficient* is a coefficient appearing in the virial equation of state of
a gas which describes the deviation from ideal gas behaviour. This coefficient describes pair
interaction between molecules of the substance and can be found if the pair interaction potential
is known, but it can also be derived from the equation of state as a series expansion with respect
to inverse molar volume or equivalently, to molar density.

**Notation:**

#. :math:`R` (:code:`R`) is :attr:`~symplyphysics.quantities.molar_gas_constant`.

**Notes:**

#. Also see :ref:`Virial equation`.

**Conditions:**

#. The gas density is small enough within the context of perturbation theory.

**Links:**

#. `Wikipedia <https://en.wikipedia.org/wiki/Van_der_Waals_equation#Virial_expansion>`__.

.. py:currentmodule:: symplyphysics.laws.thermodynamics.equations_of_state.van_der_waals.second_virial_coefficient

.. py:data:: second_virial_coefficient

    Second virial coefficient of the virial expansion.

Symbol:
    :code:`C_2`

Latex:
    :math:`C_{2}`

Dimension:
    :code:`volume/amount_of_substance`


.. py:data:: attractive_forces_parameter

    :attr:`~symplyphysics.symbols.thermodynamics.attractive_forces_parameter`.

Symbol:
    :code:`a`

Latex:
    :math:`a`

Dimension:
    :code:`pressure*volume**2/amount_of_substance**2`


.. py:data:: excluded_volume_parameter

    :attr:`~symplyphysics.symbols.thermodynamics.excluded_volume_parameter`.

Symbol:
    :code:`b`

Latex:
    :math:`b`

Dimension:
    :code:`volume/amount_of_substance`


.. py:data:: temperature

    :attr:`~symplyphysics.symbols.thermodynamics.temperature` of the van der Waals fluid.

Symbol:
    :code:`T`

Latex:
    :math:`T`

Dimension:
    :code:`temperature`


.. py:data:: law

    :code:`C_2 = b - a / (R * T)`


    Latex:
        .. math::
            C_{2} = b - \frac{a}{R T}