Interactions – Aleksandr Chernatynskiy Research Group

buck

V(r_{ij})=Ae^{-r_{ij}/\rho}-\frac{C}{r^{6}_{ij}}- \frac{D}{r^{8}_{ij}}

buck4

V(r_{ij})=\left\{\begin{matrix} Ae^{-r_{ij}/\rho},\: r_{ij}<r_1\\ 5^{th}\:degree\:poly,\: r_1<r_{ij}<r_{min}\\ 3^{rd}\:degree\:poly,\: r_{min}<r_{ij}<r_{2}\\ -\frac{C}{r^{6}_{ij}},\: r_{ij}>r_2 \end{matrix}\right.

buck_LJB

V(r_{ij})=Ae^{-r_{ij}/\rho}-\frac{C}{r^{6}_{ij}}+\frac{B_1}{(r_0+r_{ij})^{12}}+\frac{B_2}{(r_0+r_{ij})^{6}}

buck_morse1

V(r_{ij})=F_0(B_i+B_j)e^{\frac{A_i+A_j-r_{ij}}{B_i+B_j}}-\frac{C_iC_j}{r^{6}_{ij}}+D(1-(e^{-\beta(r_{ij}-r_0)}-1)^2)

buck_morse2

V(r_{ij})=Ae^{\frac{-r_{ij}}{\rho}}-\frac{C}{r^{6}_{ij}}+D(1-(e^{-\beta(r_{ij}-r_0)}-1)^2)

Lennard-Jones

V(r_{ij})=4\epsilon\left ( \left ( \frac{\sigma}{r_{ij}}\right )^{12}-\left ( \frac{\sigma}{r_{ij}}\right )^6\right )

exp-6

V(r_{ij})=\frac{\epsilon}{\alpha-6} \left ( e^{\alpha\left ( 1- \frac{r_{ij}}{\sigma}\right )}-\alpha\left ( \frac{\sigma}{r_{ij}}\right )^6\right )

Tersoff

Format:	Tersoff L
Description:	This turns on Tersoff-type potential for C, Si and Ge, as described and parametrized in the cited paper. Currently, one does not supply the values of parameters for this potential type, but they are hard-coded in the code (in force_tersoff.f90), thus only C, Si and Ge are avalable. For this potential only second derivatives are available, hence third derivatives will always be computed numerically (numerical_3der=T is set automatically). Usage of other parametrizations is possible through the LAMMPS interface.
Examples:	Tersoff T

Stillinger_weber

Format:	Stillinger_weber L
Description:	This turns on Stillinger-Weber-type potential for Si, as described and parametrized in the cited paper. Currently, one does not supply the values of parameters for this potential type, but they are hard-coded in the code (in force_SW.f90), thus only Si is avalable. For this potential only second derivatives are available (not first), hence third derivatives will always be computed numerically (numerical_3der=T is set automatically), and no quench could be performed. Usage of other parametrizations is possible through the LAMMPS interface.
Examples:	Stillinger_weber T

Tiwary

Format:	Tiwary L
Description:	This keyword turns on UO₂ potential due to Tiwary et al.. Similarly to Tersoff and Stillinger-Weber potentials this is hard-coded potential due to the large number of parameters involved. Thus, one has to have system consistent only of uranium and oxygen atoms. There is an updated version of these potentials developed for the mixed nuclear fuels that includes Pu an Np potentials in addition to U. Please contact PhonTS support if you would like to work with these potentials.
Examples:	Tiwary T

spring

V(r_{ij})=\frac{k_2}{2}r_{ij}^2

spring4

V(r_{ij})=\frac{k_2}{24}r_{ij}^4

taper

V(r_{ij})=V(r_{ij})-\left. \frac{\partial V(r_{ij})}{\partial r_{ij}} \right |_{r_{ij}=r_{cut}}\left ( r_{ij}-r_{cut} \right )