Square shoulder model

The square shoulder model is given by

$\Phi _{12}\left(r\right)=\left\{{\begin{array}{ccc}\infty &;&r<\sigma \\\epsilon &;&\sigma \leq r<\lambda \sigma \\0&;&r\geq \lambda \sigma \end{array}}\right.$

where $\Phi _{12}(r)$ is the intermolecular pair potential, $\epsilon$ is the height of the shoulder, $r$ is the distance between site 1 and site 2 $r:=|\mathbf {r} _{1}-\mathbf {r} _{2}|$, σ is the hard diameter and λ > 1.

Direct correlation function

The direct correlation function

References

Related reading

• A R Denton and H Löwen "Isostructural solid - solid transitions in square-shoulder systems", Journal of Physics: Condensed Matter 9 pp. L1-L5 (1997)
• Peter Bolhuis and Daan Frenkel "Isostructural solid - solid transitions in systems with a repulsive `shoulder' potential", Journal of Physics: Condensed Matter 9 pp. 381-387 (1997)
• Andreas Lang, Gerhard Kahl, Christos N Likos, Hartmut Löwen and Martin Watzlawek "Structure and thermodynamics of square-well and square-shoulder fluids", Journal of Physics: Condensed Matter 11 pp. 10143-10161 (1999)
• Gernot J. Pauschenwein and Gerhard Kahl "Zero temperature phase diagram of the square-shoulder system", Journal of Chemical Physics 129 174107 (2008)
• Shiqi Zhou and J. R. Solana "Inquiry into thermodynamic behavior of hard sphere plus repulsive barrier of finite height", Journal of Chemical Physics 131 204503 (2009)
• S. B. Yuste, A. Santos and M. López de Haro "Structure of the square-shoulder fluid", Molecular Physics 109 pp. 987-995 (2011)