Hard sphere model

Interaction Potential

The hard sphere intermolecular pair potential is given by

$\Phi \left(r\right)=\left\{{\begin{array}{lll}\infty &;&r<\sigma \\0&;&r\geq \sigma \end{array}}\right.$

where $\Phi \left(r\right)$ is the intermolecular pair potential between two spheres at a distance $r$, and $\sigma$ is the diameter of the sphere.

Equations of state

See: Equations of state for hard spheres (for example, the celebrated Carnahan-Starling equation of state). For the virial equation of state associated with the hard sphere model see: Hard sphere: virial coefficients

Fluid-solid transition

The hard sphere system undergoes a fluid-solid first order transition at $\rho d^{3}=0.94$, $\eta _{A}={\frac {\pi \rho d^{3}}{6}}=0.49218$.

• William G. Hoover and Francis H. Ree "Melting Transition and Communal Entropy for Hard Spheres", Journal of Chemical Physics 49 pp. 3609-3617 (1968)

Solid structure

• Leslie V. Woodcock "Computation of the free energy for alternative crystal structures of hard spheres", Faraday Discussions 106 pp. 325 - 338 (1997)

First simulations of hard spheres

• Marshall N. Rosenbluth and Arianna W. Rosenbluth "Further Results on Monte Carlo Equations of State", Journal of Chemical Physics 22 pp. 881-884 (1954)
• W. W. Wood and J. D. Jacobson "Preliminary Results from a Recalculation of the Monte Carlo Equation of State of Hard Spheres", Journal of Chemical Physics 27 pp. 1207-1208 (1957)
• B. J. Alder and T. E. Wainwright "Phase Transition for a Hard Sphere System", Journal of Chemical Physics 27 pp. 1208-1209 (1957)

Experimental results

Pusey and van Megen used a suspension of PMMA particles of radius 305 $\pm$10 nm, suspended in poly-12-hydroxystearic acid:

• P. N. Pusey and W. van Megen "Phase behaviour of concentrated suspensions of nearly hard colloidal spheres", Nature 320 pp. 340 - 342 (1986)

For results obtained from the Colloidal Disorder - Order Transition (CDOT) experiments performed on-board the Space Shuttles Columbia and Discovery see Ref. 3.

External links

• Hard disks and spheres computer code on SMAC-wiki.

Related systems

• Polydisperse hard spheres
• Quantum hard spheres
• Dipolar hard spheres

Hard spheres in other dimensions

• 1-dimensional case: hard rods.
• 2-dimensional case: hard disks.
• Hard hyperspheres

References

1. Robin J. Speedy "Pressure of the metastable hard-sphere fluid", Journal of Physics: Condensed Matter 9 pp. 8591-8599 (1997)
2. Robin J. Speedy "Pressure and entropy of hard-sphere crystals", Journal of Physics: Condensed Matter 10 pp. 4387-4391 (1998)
3. Z. Chenga, P. M. Chaikina, W. B. Russelb, W. V. Meyerc, J. Zhub, R. B. Rogersc and R. H. Ottewilld, "Phase diagram of hard spheres", Materials & Design 22 pp. 529-534 (2001)