“…Th e monomer symmetry is one of axial point groups (groups of transformations that leave z-axis invariant). Th ese are C n (successive rotations C n by 2π/n around z-axis, n=1,2,…), S 2n , C nh , C nv , D n (which combine C n with rotation by π/n followed by horizontal mirror refl ection, horizontal and vertical mirror plane and rotation U by π around x-axis, respectively) and D nd and [2]) to make L W@W' fi nite: equi-energetic positions are continual along Z, and E(Φ,Z) is constant along Z. Walls are super slippery as their mutual translation costs no energy.…”