Figure 2.

Selection of different rotation potentials discussed in the text and definition of notation. All four potentials V (color coded) are shown for a single atom at position x_j(t). (A) Isotropic potential V^iso, (B) radial motion potential V^rm and flexible potential V^flex, (C,D) radial motion 2 potential V^rm2 and flexible 2 potential V^flex2 for ε′ = 0 nm² (C) and ε′ = 0.01 nm² (D). The rotation axis is perpendicular to the plane and marked by ⊗. The light gray contours indicate Boltzmann factors e^−V/(k_BT) in the x_j plane for T = 300 K and k = 200 kJ/(mol·nm²). The green arrow shows the direction of the force F_j acting on atom j; the blue dashed line indicates the motion of the reference position.