Structural trends in clusters of quadrupolar spheres

Abstract

The influence of quadrupolar interactions on the structure of small clusters is investigated by adding a point quadrupole of variable strength to the Lennard-Jones potential. Competition arises between sheet-like arrangements of the particles, favoured by the quadrupoles, and compact structures, favoured by the isotropic Lennard-Jones attraction. Putative global potential energy minima are obtained for clusters of up to 25 particles using the basin-hopping algorithm. A number of structural motifs and growth sequences emerge, including star-like structures, tubes, shells and sheets. The results are discussed in the context of colloidal self-assembly.

Keywords:

• global optimisation
• clusters
• energy landscapes
• self-assembly

Acknowledgements

The authors are grateful to Josef O'Brien for some preliminary calculations on Lennard–Jones clusters with extended quadrupolar distributions of point charges. MAM thanks EPSRC for financial support.