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Phase diagram of SALR fluids on spherical surfaces
Stefano Franzini1, Luciano Reatto1, Davide Pini1
1Dipartimento di Fisica "A. Pontremoli", Università di Milano, Via Celoria 16, 20133 Milano, Italy. stefano.franzini93@gmail.com.
Soft Matter
|December 3, 2021
Summary
We studied disk fluids on a sphere with specific interactions. We found new patterns like cluster crystals and stripes, influenced by system size and particle interactions.
Area of Science:
- Soft matter physics
- Statistical mechanics
- Computational physics
Background:
- Understanding fluid phase behavior is crucial in statistical mechanics.
- Confining systems to curved surfaces introduces unique phenomena not seen in bulk.
- The specific short-range attraction and long-range repulsion (SALR) potential is relevant for modeling various soft matter systems.
Purpose of the Study:
- To investigate the phase diagram of hard-core disks with SALR interactions confined to a spherical surface.
- To identify stability criteria for the homogeneous fluid phase under these conditions.
- To characterize the resulting inhomogeneous phases and their dependence on system parameters.
Main Methods:
- Derivation of a stability criterion for the homogeneous phase based on bulk fluid theory.
- Application of mean-field density functional theory to analyze inhomogeneous phases.
- Analysis of the spherical harmonics expansion of the interaction potential to identify instability regions.
Main Results:
- A region of instability was identified, linked to a negative minimum in the interaction potential's spherical harmonics expansion.
- Several inhomogeneous phases were discovered, categorized as cluster crystals, stripes, and bubble crystals, all exhibiting topological defects.
- The periodicity of these phases at high densities is dictated by the potential's minimum, while finite system size leads to complex behavior at lower densities.
Conclusions:
- The SALR potential on a sphere leads to diverse inhomogeneous phases beyond simple fluid or solid states.
- Topological defects play a significant role in the structure of these ordered phases.
- System size and interaction potential details critically influence the observed phase behavior, highlighting the importance of confinement effects.
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