Spectral distributions for the average coordinate for a circular DQW. The symbols correspond to discretization of the Schrödinger equation on various numerical meshes. The meshes differ by the elements minimum size. The energy splitting () of the quasidoublet of the ground state for each discretization of a mesh is given in the inset. The finer mesh corresponds to smaller . Interdot distance is kept the same and equal to 26 nm.