Helical and antiparallel structures from truncated long-range interactions in water and dipolar spins

Abstract

It is known that dipolar systems such as water produce highly ordered layered structures when long-range dipolar interactions are truncated at a finite distance. However, many parts of this long-range phenomenon remain unsolved. Herein, we fundamentally explored this phenomenon using Monte Carlo simulations for dipolar spins and molecular dynamics simulations for water. The results show that the width of the layers does not depend on the system size but is determined by the cutoff length. At the same time, layer formation occurred even without periodic boundary conditions. These results suggest that layer formation is a consequence of cutoff rather than the periodic boundary conditions. We also found that water has a helical dipole distribution, whereas dipolar spin has an antiparallel distribution, with these two forms being energetically competing. Our findings on the relationship between long-range interactions and the resulting structures are expected to contribute to future explorations of structures with similar ordering in magnetic, dielectric, and soft materials.