def _set_ref_state(self):
        calc = self.calculators['gamma']
        path_const = calc.path_const

        if path_const=='S':
            param_ref_names = []
            param_ref_units = []
            param_ref_defaults = []
            param_ref_scales = []
        else:
            raise NotImplementedError(
                'path_const '+path_const+' is not valid for ThermalEos.')

        self._path_const = calc.path_const
        self._param_ref_names = param_ref_names
        self._param_ref_units = param_ref_units
        self._param_ref_defaults = param_ref_defaults
        self._param_ref_scales = param_ref_scales
        pass