Merge pull request #394 from jaapkroe/kolmogorov-crespi

Added Kolmogorov-Crespi potential

doc/src/Eqs/pair_kolmogorov_crespi_z.tex

@@ -0,0 +1,13 @@
+\documentclass[12pt]{article}
+\thispagestyle{empty}
+
+\begin{document}
+
+\begin{eqnarray*}
+  E & = & \frac{1}{2} \sum_i \sum_{j \neq i} V_{ij} \\
+  V_{ij} & = & e^{-\lambda(r_{ij} -z_0}) \left[ C + f(\rho_{ij}) + f(\rho_{ji}) \right] - A \left( \frac{r_{ij}}{z_0}\right)^{-6} + A \left( \frac{\textrm{cutoff}}{z_0}\right)^{-6} \\
+  \rho_{ij}^2 = \rho_{ji}^2 & = &  x_{ij}^2 + y_{ij}^2 ~\hspace{2cm} (\mathbf{n_i}\equiv\hat \mathbf{z})\\
+  f(\rho) & = &  e^{-(\rho/\delta)^2} \sum_{n=0}^2 C_{2n} \left( \rho/\delta \right) ^{2n}
+\end{eqnarray*}
+
+\end{document}

doc/src/Section_commands.txt

@@ -1016,6 +1016,7 @@ package"_Section_start.html#start_3.
 "eff/cut"_pair_eff.html,
 "exp6/rx"_pair_exp6_rx.html,
 "gauss/cut"_pair_gauss.html,
+"kolmogorov/crespi/z"_pair_kolmogorov_crespi_z.html,
 "lennard/mdf"_pair_mdf.html,
 "list"_pair_list.html,
 "lj/charmm/coul/long/soft (o)"_pair_charmm.html,

doc/src/lammps.book

@@ -434,6 +434,7 @@ pair_gromacs.html
 pair_hbond_dreiding.html
 pair_hybrid.html
 pair_kim.html
+pair_kolmogorov_crespi_z.html
 pair_lcbop.html
 pair_line_lj.html
 pair_list.html

doc/src/pair_kolmogorov_crespi_z.txt

@@ -0,0 +1,72 @@
+"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
+
+:link(lws,http://lammps.sandia.gov)
+:link(ld,Manual.html)
+:link(lc,Section_commands.html#comm)
+
+:line
+
+pair_style kolmogorov/crespi/z command :h3
+
+[Syntax:]
+
+pair_style hybrid/overlay kolmogorov/crespi/z cutoff :pre
+
+[Examples:]
+
+pair_style hybrid/overlay kolmogorov/crespi/z 20.0
+pair_coeff * * none
+pair_coeff 1 2 kolmogorov/crespi/z  CC.KC   C C :pre
+
+pair_style hybrid/overlay rebo kolmogorov/crespi/z 14.0
+pair_coeff * * rebo                 CH.airebo  C C
+pair_coeff 1 2 kolmogorov/crespi/z  CC.KC      C C :pre
+
+[Description:]
+
+The {kolmogorov/crespi/z} style computes the Kolmogorov-Crespi interaction 
+potential as described in "(KC05)"_#KC05. An important simplification is made, 
+which is to take all normals along the z-axis. 
+
+:c,image(Eqs/pair_kolmogorov_crespi_z.jpg)
+
+It is important to have a suffiently large cutoff to ensure smooth forces. 
+Energies are shifted so that they go continously to zero at the cutoff assuming 
+that the exponential part of {Vij} (first term) decays sufficiently fast.
+This shift is achieved by the last term in the equation for {Vij} above.
+
+This potential is intended for interactions between two layers of graphene. 
+Therefore, to avoid interaction between layers in multi-layered materials, 
+each layer should have a separate atom type and interactions should only 
+be computed between atom types of neighbouring layers.
+
+The parameter file (e.g. CC.KC), is intended for use with metal 
+"units"_units.html, with energies in meV. An additional parameter, {S}, 
+is available to facilitate scaling of energies in accordance with 
+"(vanWijk)"_#vanWijk.
+
+This potential must be used in combination with hybrid/overlay.
+Other interactions can be set to zero using pair_style {none}.
+
+[Restrictions:]
+
+This fix is part of the USER-MISC package.  It is only enabled if
+LAMMPS was built with that package.  See the "Making
+LAMMPS"_Section_start.html#start_3 section for more info.
+
+[Related commands:]
+
+"pair_coeff"_pair_coeff.html
+"pair_none"_pair_none.html
+"pair_style hybrid/overlay"_pair_hybrid.html
+
+[Default:] none
+
+:line
+
+:link(KC05) 
+[(KC05)] A. N. Kolmogorov, V. H. Crespi, Phys. Rev. B 71, 235415 (2005)
+
+:link(vanWijk) 
+[(vanWijk)] M. M. van Wijk, A. Schuring, M. I. Katsnelson, and A. Fasolino, 
+Physical Review Letters, 113, 135504 (2014)

doc/src/pairs.txt

@@ -39,6 +39,7 @@ Pair Styles :h1
    pair_hbond_dreiding
    pair_hybrid
    pair_kim
+   pair_kolmogorov_crespi_z
    pair_lcbop
    pair_line_lj
    pair_list