Soft spheres make more mesophases

¹  Department of Physics, University of Colorado - Boulder, CO 80309-0390, USA
²  Department of Physics and Astronomy, University of California at Los Angeles - Los Angeles CA 90024, USA
³  Department of Physics and Astronomy, University of Pennsylvania - Philadelphia, PA 19104, USA
⁴  Massachusetts Institute of Technology - Cambridge, MA 02139-4307, USA
⁵  Department of Physics, University of Ljubljana - Jadranska 19, SI-1000 Ljubljana, Slovenia and Jožef Stefan Institute - Jamova 39, SI-1000 Ljubljana, Slovenia

Received: 18 January 2007
Accepted: 9 April 2007

Abstract

We use both mean-field methods and numerical simulation to study the phase diagram of classical particles interacting with a hard core and repulsive, soft shoulder. Despite the purely repulsive and isotropic interaction, this system displays a remarkable array of aggregate phases arising from the competition between the hard-core and soft-shoulder length scales, including fluid and crystalline phases with micellar, lamellar, and inverse micellar morphology. In the limit of large shoulder width to core size, we argue that this phase diagram has a number of universal features, and classify the set of repulsive shoulders that lead to aggregation at high density. Surprisingly, the phase sequence and aggregate size adjust so as to keep almost constant inter-aggregate separation.