def get_wfn_variables(**kwargs):
    """Return a dict of variables required for an SCF calculation."""
    variables = dict(
        irdden = 1,
        nband = kwargs.get('nband'),
        ecut = kwargs.get('ecut'),
        tolwfr = kwargs.get('tolwfr', 1e-14),
        iscf = kwargs.get('iscf', -3),
        istwfk = kwargs.get('istwfk', '*1'),
        )
    return variables