pair_style lj/cleavcutNlint

Syntax

pair_style lj/cleavcutNlint cutoff lambda i_IDflag orientation alpha

  • cutoff = global internal cut-off

  • lambda = global scaling of the potential

  • i_IDflag = new (integer) property to be added to the atoms

  • orientation = direction perpendicular to the cleaving plane

  • N = power of the polynomial for \(\lambda\)

  • rs = short range switching (distance units)

pair_coeff accepts only the following arguments

pair_coeff a b lambda

where

a        = atom of type a [mandatory]
b        = atom of type b [mandatory]
epsilon  = energy constant (energy units)
sigma    = VdW radius (distance units)
lambda   = scaling of the potential
cut-off  = cut-off for LJ potential (distance units)

Description

This pair style is derived from the pair/ljcut in LAMMPS and we refer to the LAMMPS documentation for the description of its main features. Here, only the modifications needed for the cleaving calculations will be considered.

This pair style modifies the short range portion of the Lennard-Jones potential in order to avoid the “Lennard-Jones catastrophe”. The potential is modified by smoothly interpolating it to zero for distances smaller than \(r_s\) as:

\[\begin{split} U(r_{ln}) = \begin{cases} A_0 + A_1 \left( \frac{r}{r_s}^3 + A_2 \frac{r}{r_s}^4 \right)\; r_{ln} \leq r_{s} \\ 4\epsilon\left(\left(\frac{\sigma}{r_{ln}}\right)^{12} -\left(\frac{\sigma}{r_{ln}}\right)^{6} \right)+C_1,\;\mbox{if}\; r_{ln} \leq r_{cut} \end{cases} \end{split}\]

where \(r_{ln}=|\mathbf{r}_l-\mathbf{r}_n|\) for each couple of atoms \(l,n\) in the system, \(r_{cut}\) is the cut-off for the potential and \(A_0\), \(A_1\), \(A_2\) are three constant which ensure that the potential has continuous first and second derivative in \(r_s\). These contants depends on \(r_c\) and are calculated internally so they do not need to be specified.

The description of the cleaving methodology using this pair style is analogous to the one described for the pair style coul/dsf[cleav] to which we refer.