Figure 1.

1D water wires in nanopores. (a) Chain configuration with a D-defect and an L-defect, and the corresponding lattice model in the (b) dipole representation, (c) the segment representation, and (d) the effective charge representation. In the lattice model, sites are marked by filled circles, dipoles are represented by short arrows, segments by long arrows, and effective charges by circles with their sign at the center. (a) The D-defect molecule accepts two hydrogen bonds from the two neighboring water molecules; in contrast, the L-defect molecule donates two hydrogen bonds. (b) The next-neighbor dipoles of the defect sites point to the defect site for the D-defect and away from it for the L-defect. (c) The configurational energy of the water wire due to the dipoles is determined by the length, orientation, and distance of segments. (d) In the effective charge representation, the segments are replaced by charges at the ends with signs according to their orientations. As a consequence, defects are formed by pairs of equal charges which are positive for the D-defect and negative for the L-defect.