def mp2d_coeff_formatter(dashlvl, dashcoeff):
    """Return strings for MP2D program parameter file.

    Parameters
    ----------
    dashlvl : {'dmp2'}
        Level of dispersion correction.
    dashcoeff : dict
        Dictionary fully specifying non-fixed parameters for `dashlvl` to drive MP2D.

    Returns
    -------
    str
        Suitable for `Params.txt` file.

    """
    dashformatter = """a_one: {:.6f} a_two: {:.6f} rcut: {:.6f} width: {:.6f} s_8: {:.6f}\n"""

    dashlvl = dashlvl.lower()
    if dashlvl == 'dmp2':
        return dashformatter.format(dashcoeff['a1'], dashcoeff['a2'], dashcoeff['rcut'], dashcoeff['w'], dashcoeff['s8'])
    else:
        raise ValueError(
            """-D correction level %s is not available. Choose among %s.""" % (dashlvl, dashcoeff.keys()))