Merge pull request #1453 from mjwen/pair_drip

"dpd/fdt/energy (k)"_pair_dpd_fdt.html,

"dpd/tstat (go)"_pair_dpd.html,

"dsmc"_pair_dsmc.html,

"drip"_pair_drip.html,

"eam (gikot)"_pair_eam.html,

"eam/alloy (gikot)"_pair_eam.html,

"eam/cd (o)"_pair_eam.html,

\documentclass[12pt]{article}

\usepackage{amsmath}

\usepackage{bm}

\begin{document}

\begin{eqnarray*}

E &=& \frac{1}{2} \sum_{i} \sum_{j\notin\text{layer}\,i} \phi_{ij} \\\phi_{ij} &=& f_\text{c}(x_r) \left[ e^{-\lambda(r_{ij} - z_0 )} \left[C+f(\rho_{ij})+  g(\rho_{ij}, \{\alpha_{ij}^{(m)}\}) \right]- A\left (\frac{z_0}{r_{ij}} \right)^6 \right] \\

\end{eqnarray*}  

\end{document}

 No newline at end of file

pair_dpd.html

pair_dpd_fdt.html

pair_dsmc.html

pair_drip.html

pair_eam.html

pair_edip.html

pair_eff.html

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)

:link(ld,Manual.html)

:link(lc,Commands_all.html)

:line

pair_style drip command :h3

[Syntax:]

pair_style hybrid/overlay drip \[styles ...\] :pre

styles = other styles to be overlayed with drip (optional) :ul

[Examples:]

pair_style hybrid/overlay drip

pair_coeff * * none

pair_coeff * * drip  C.drip  C :pre

pair_style hybrid/overlay drip rebo

pair_coeff * * drip  C.drip     C

pair_coeff * * rebo  CH.airebo  C :pre

pair_style hybrid/overlay drip rebo

pair_coeff * * drip  C.drip     C NULL

pair_coeff * * rebo  CH.airebo  C H :pre

[Description:]

Style {drip} computes the interlayer interactions of layered materials using

the dihedral-angle-corrected registry-dependent (DRIP) potential as described

in "(Wen)"_#Wen2018, which is based on the "(Kolmogorov)"_#Kolmogorov2005

potential and provides an improved prediction for forces.

The total potential energy of a system is

:c,image(Eqs/pair_drip.jpg)

where the {r^-6} term models the attractive London dispersion,

the exponential term is designed to capture the registry effect due to

overlapping {pi} bonds, and {fc} is a cutoff function.

This potential (DRIP) only provides the interlayer interactions between

graphene layers. So, to perform a realistic simulation, it should be used in

combination with an intralayer potential such as "REBO"_pair_airebo.html and

"Tersoff"_pair_tersoff.html.

To keep the intralayer interactions unaffected, we should avoid applying DRIP

to contribute energy to intralayer interactions. This can be achieved by

assigning different molecular IDs to atoms in different layers, and DRIP is

implemented such that only atoms with different molecular ID can interact with

each other. For this purpose, "atom style"_atom_style.html "molecular" or

"full" has to be used.

On the other way around, "REBO"_pair_airebo.html ("Tersoff"_pair_tersoff.html

or any other potential used to provide the intralayer interactions) should not

interfere with the interlayer interactions described by DRIP. This is typically

automatically achieved using the commands provided in the {Examples} section

above, since the cutoff distance for carbon-carbon interaction in the intralayer

potentials (e.g. 2 Angstrom for "REBO"_pair_airebo.html) is much smaller than

the equilibrium layer distance of graphene layers (about 3.4 Angstrom).

If you want, you can enforce this by assigning different atom types to atoms in

different layers, and apply an intralayer potential to one atom type.

See "pair_hybrid"_pair_hybrid.html for details.

:line

The "pair_coeff"_pair_coeff.html command for DRIP takes {4+N} arguments, where

{N} is the number of LAMMPS atom types. The fist three arguments must be fixed

to be {* * drip}, the fourth argument is the path to the DRIP parameter file,

and the remaining N arguments specifying the mapping between element in the

parameter file and atom types. For example, if your LAMMPS simulation has 3 atom

types and you want all of them to be C, you would use the following pair_coeff

command:

pair_coeff * * drip  C.drip  C C C :pre

If a mapping value is specified as NULL, the mapping is not performed. This

could be useful when DRIP is used to model part of the system where other

element exists. Suppose you have a hydrocarbon system, with C of atom type 1

and H of atom type 2, you can use the following command to inform DRIP not to

model H atoms:

pair_style hybrid/overlay drip rebo

pair_coeff * * drip  C.drip     C NULL

pair_coeff * * rebo  CH.airebo  C H :pre

NOTE: The potential parameters developed in "(Wen)"_#Wen2018 are provided with

LAMMPS (see the "potentials" directory). Besides those in "Wen"_#Wen2018, an

additional parameter "normal_cutoff", specific to the LAMMPS implementation, is

used to find the three nearest neighbors of an atom to construct the normal.

:line

[Mixing, shift, table, tail correction, and restart info]:

This pair style does not support the pair_modify mix, shift, table,

and tail options.

This pair style does not write their information to binary restart files, since

it is stored in potential files. Thus, you need to re-specify the pair_style and

pair_coeff commands in an input script that reads a restart file.

[Restrictions:]

This pair style is part of the USER-MISC package. It is only enabled if LAMMPS

was built with that package.  See the "Build package"_Build_package.html doc

page for more info.

This pair potential requires the "newton"_newton.html setting to be "on" for

pair interactions.

The {C.drip} parameter file provided with LAMMPS (see the "potentials"

directory) is parameterized for metal "units"_units.html. You can use the DRIP

potential with any LAMMPS units, but you would need to create your own custom

parameter file with coefficients listed in the appropriate units, if your

simulation doesn't use "metal" units.

[Related commands:]

"pair_style lebedeva_z"_pair_lebedeva_z.html,

"pair_style kolmogorov/crespi/z"_pair_kolmogorov_crespi_z.html,

"pair_style kolmogorov/crespi/full"_pair_kolmogorov_crespi_full.html,

"pair_style ilp/graphene/hbn"_pair_ilp_graphene_hbn.html.

:line

:link(Wen2018)

[(Wen)] M. Wen, S. Carr, S. Fang, E. Kaxiras, and E. B. Tadmor, Phys. Rev. B,

98, 235404 (2018)

:link(Kolmogorov2005)

[(Kolmogorov)] A. N. Kolmogorov, V. H. Crespi, Phys. Rev. B 71, 235415 (2005)