def _phiforce(self,R,z,phi=0.,t=0.):
        """
        NAME:
           _phiforce
        PURPOSE:
           evaluate the azimuthal force for this potential
        INPUT:
           R - Galactocentric cylindrical radius
           z - vertical height
           phi - azimuth
           t - time
        OUTPUT:
           the azimuthal force
        HISTORY:
           2016-12-26 - Written - Bovy (UofT)
        """
        return self._scf.phiforce(R,z,phi=phi,use_physical=False)