pair_style lebedeva/z command

Accelerator Variants: lebedeva/z/omp

Syntax

pair_style [hybrid/overlay ...] lebedeva/z cutoff

Examples

pair_style hybrid/overlay lebedeva/z 20.0
pair_coeff * * none
pair_coeff 1 2 lebedeva/z  CC.Lebedeva   C C

pair_style hybrid/overlay rebo lebedeva/z 14.0
pair_coeff * * rebo        CH.rebo       C C
pair_coeff 1 2 lebedeva/z  CC.Lebedeva   C C

Description

The lebedeva/z pair style computes the Lebedeva interaction potential as described in (Lebedeva1) and (Lebedeva2). An important simplification is made, which is to take all normals along the z-axis.

The Lebedeva potential is intended for the description of the interlayer interaction between graphene layers. To perform a realistic simulation, this potential must be used in combination with an intralayer potential such as AIREBO or Tersoff facilitated by using pair style hybrid/overlay. To keep the intralayer properties unaffected, the interlayer interaction within the same layers should be avoided. This can be achieved by assigning different atom types to atoms of different layers (e.g. 1 and 2 in the examples above).

Other interactions can be set to zero using pair_style none.

\[\begin{split}E = & \frac{1}{2} \sum_i \sum_{j \neq i} V_{ij}\\ V_{ij} = & B e^{-\alpha(r_{ij} - z_0)} \\ & + C(1 + D_1\rho^2_{ij} + D_2\rho^4_{ij}) e^{-\lambda_1\rho^2_{ij}} e^{-\lambda_2 (z^2_{ij} - z^2_0)} \\ & - A \left(\frac{z_0}{r_ij}\right)^6 + A \left( \frac{z_0}{r_c} \right)^6 \\ \rho^2_{ij} = & x^2_{ij} + y^2_{ij} \qquad (\mathbf{n_i} \equiv \mathbf{\hat{z}})\end{split}\]

It is important to have a sufficiently large cutoff to ensure smooth forces. Energies are shifted so that they go continuously to zero at the cutoff assuming that the exponential part of \(V_{ij}\) (first term) decays sufficiently fast. This shift is achieved by the last term in the equation for \(V_{ij}\) above.

The provided parameter file (CC.Lebedeva) contains two sets of parameters.

The first set (element name “C”) is suitable for normal conditions and is taken from (Popov1)
The second set (element name “C1”) is suitable for high-pressure conditions and is taken from (Koziol1)

Both sets contain an additional parameter, S, that can be used to facilitate scaling of energies and is set to 1.0 by default.

Styles with a gpu, intel, kk, omp, or opt suffix are functionally the same as the corresponding style without the suffix. They have been optimized to run faster, depending on your available hardware, as discussed on the Accelerator packages page. The accelerated styles take the same arguments and should produce the same results, except for round-off and precision issues.

These accelerated styles are part of the GPU, INTEL, KOKKOS, OPENMP, and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the Build package page for more info.

You can specify the accelerated styles explicitly in your input script by including their suffix, or you can use the -suffix command-line switch when you invoke LAMMPS, or you can use the suffix command in your input script.

See the Accelerator packages page for more instructions on how to use the accelerated styles effectively.

Restrictions

This pair style is part of the INTERLAYER package. It is only enabled if LAMMPS was built with that package. See the Build package page for more info.

Default

none

(Lebedeva1) I. V. Lebedeva, A. A. Knizhnik, A. M. Popov, Y. E. Lozovik, B. V. Potapkin, Phys. Rev. B, 84, 245437 (2011)

(Lebedeva2) I. V. Lebedeva, A. A. Knizhnik, A. M. Popov, Y. E. Lozovik, B. V. Potapkin, Physica E: 44, 949-954 (2012)

(Popov1) A.M. Popov, I. V. Lebedeva, A. A. Knizhnik, Y. E. Lozovik and B. V. Potapkin, Chem. Phys. Lett. 536, 82-86 (2012).

(Koziol1) Z. Koziol, G. Gawlik and J. Jagielski, Chinese Phys. B 28, 096101 (2019).