From Crystals to Disordered Crystals: A Hidden Order-Disorder Transition

Area of Science:

• Physics
• Materials Science
• Condensed Matter Physics

Background:

• Distinguishing between order and disorder is crucial for understanding solid properties.
• High-order solids can exhibit disordered behavior, and disordered solids can approach crystalline properties under specific conditions.
• Understanding the factors controlling solid behavior and the onset of disorder is imperative.

Purpose of the Study:

• To identify and characterize a hidden order-disorder transition in static packings of frictionless spheres.
• To determine the factors governing this transition and the properties of the resulting disordered crystals.
• To investigate the distinct pressure dependence of elastic moduli and coordination number near the transition.

Main Methods:

• Analysis of static packings of frictionless spheres.
• Investigation of geometric indicators for the order-disorder transition.
• Examination of properties like elastic moduli and coordination number under varying pressure and density.

Main Results:

• Discovery of a hidden order-disorder transition from crystals to disordered crystals.
• Geometric indicators are largely insensitive to this transition.
• Disordered crystals exhibit unique properties distinct from both crystals and jammed solids, particularly near the close packing singularity.
• The transition and properties are jointly controlled by structural order and density.

Conclusions:

• A novel order-disorder transition exists in frictionless sphere packings.
• Disordered crystals possess distinct properties influenced by structural order and density.
• The transition reveals previously unknown aspects of solid behavior, particularly concerning elastic moduli and coordination number dependence on pressure.