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

Main article: Equations of state for the square shoulder model

References

Related reading

• J. M. Kincaid, G. Stell and E. Goldmark "Isostructural phase transitions due to core collapse. II. A three-dimensional model with a solid–solid critical point", Journal of Chemical Physics 65 pp. 2172-2179 (1976)
• 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)