Morse

[classi] [classj] morse [eps] [rho] [r_e]

UMorse = ε$$\left[\vphantom{1 - \exp\left\{ -\rho \left(r - r_e\right) \right\} }\right.$$1 - exp$$\left\{\vphantom{ -\rho \left(r - r_e\right) }\right.$$ - ρ$$\left(\vphantom{r - r_e}\right.$$r - re$$\left.\vphantom{r - r_e}\right)$$$$\left.\vphantom{ -\rho \left(r - r_e\right) }\right\}$$$$\left.\vphantom{1 - \exp\left\{ -\rho \left(r - r_e\right) \right\} }\right]^{2}_{}$$ - 1

(14)

where ε is the energy scale, ρ is the range parameter, and r_e is the equilibrium bond distance (or length scale).