def square(target, pore_diameter='pore.diameter'):
    """
    Calculate pore volume from diameter assuming a cubic pore body

    Parameters
    ----------
    target : OpenPNM Object
        The object which this model is associated with. This controls
        the length of the calculated array, and also provides access to other
        necessary geometric properties.

    pore_diameter : string
        The dictionary key of the pore diameter values

    """
    return target[pore_diameter] ** 2
