def string_to_functional(dict_string):
    """
    Turn input string for function option into a (string, dictionary) representing
    the functional to be used in calculations.

    Args:
        dict_string: String that provides the string/float pairs, separated by a
            space.

    Returns:
        tuple: Tuple of (String that represents the functional, Dictionary of
            string/float pairs).

    """
    dict_pairs = dict_string.split(" ")

    functional = dict_pairs[0]
    functional_dict = dict(
        zip(dict_pairs[1::2], [float(number) for number in dict_pairs[2::2]])
    )

    # Turn functional string into dict
    if functional == "pbeu":
        pbeu_dict = dict()
        pbeu_dict["LDAUU"] = functional_dict
        return functional, pbeu_dict
    else:
        return functional, functional_dict