Sound Velocity
r = 0.982The strongest single correlation in Synchronism's chemistry work: the speed of sound in a material correlates with its coherence parameter at r = 0.982.
Why This Works
Sound is a collective excitation — atoms vibrating in coordination. The speed of sound directly reflects how strongly atoms are coupled to their neighbors. This IS what γ measures: the degree of collective correlation.
Materials with high sound velocity (diamond: 12,000 m/s) have strongly correlated atomic motion (low γ, highly coherent). Materials with low sound velocity (lead: 1,190 m/s) have weakly correlated atomic motion (higher γ, less coherent).
What It Tells Us
This correlation validates the fundamental idea: γ = 2/√Ncorrgenuinely captures something physical about collective behavior. When Ncorr is large (many atoms moving together), sound travels fast and γ is small.
Limitation
The correlation is for elemental solids. Complex materials (alloys, polymers, composites) have additional structure that γ alone can't capture. The r = 0.982 applies to the periodic table, not to arbitrary materials.