Square shoulder model

The square shoulder model is given by

${\mathrm{\Phi }}_{12}(r)=\{\begin{array}{ccc}\mathrm{\infty }& ;& r<\sigma \\ ϵ& ;& \sigma \le r<\lambda \sigma \\ 0& ;& r\ge \lambda \sigma \end{array}$

where ${\mathrm{\Phi }}_{12}(r)$ is the intermolecular pair potential, $ϵ$ 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

Equation of State

.

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)
• 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)
• S. P. Hlushak, P. A. Hlushak, and A. Trokhymchuk "An improved first-order mean spherical approximation theory for the square-shoulder fluid", Journal of Chemical Physics 138 164107 (2013)
• M. López de Haro, S. B. Yuste and A. Santos "Theoretical approaches to the structural properties of the square-shoulder fluid", Molecular Physics 114 pp. 2382-2390 (2016)