def __init__(self, kind='GammaPowLaw', natom=1, model_state={}):
        self._pre_init(natom=natom)

        set_calculator(self, kind, self._kind_opts)

        ref_compress_state='P0'
        ref_thermal_state='T0'
        ref_energy_type = 'E0'
        refstate.set_calculator(self, ref_compress_state=ref_compress_state,
                                ref_thermal_state=ref_thermal_state,
                                ref_energy_type=ref_energy_type)
        # self._set_ref_state()
        self._post_init(model_state=model_state)

        pass