Merge pull request #669 from urpedersen/master

\documentclass[12pt]{article}

\begin{document}

\begin{eqnarray*}

 U &=&  \frac{1}{2} K (|\rho_{\vec{k}}| - a)^2 \\

 \rho_{\vec{k}} &=& \sum_j^N \exp(-i\vec{k} \cdot \vec{r}_j )/\sqrt{N} \\

 \vec{k} &=& (2\pi n_x /L_x , 2\pi n_y  /L_y , 2\pi n_z/L_z ) 

\end{eqnarray*}

\end{document}

"qtb"_fix_qtb.html,

"reax/c/bonds"_fix_reax_bonds.html,

"reax/c/species"_fix_reaxc_species.html,

"rhok"_fix_rhok.html,

"rx"_fix_rx.html,

"saed/vtk"_fix_saed_vtk.html,

"shardlow"_fix_shardlow.html,

"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

fix rhok command :h3

fix ID group-ID rhok nx ny nz K a :pre

ID, group-ID are documented in "fix"_fix.html command

nx, ny, nz = k-vektor of collective density field

K = spring constant of bias potential

a = anchor point of bias potential :ul

[Examples:]

fix bias all rhok 16 0 0 4.0 16.0

fix 1 all npt temp 0.8 0.8 4.0 z 2.2 2.2 8.0

# output                             U_bias rho_k_RE  rho_k_IM  |rho_k|

thermo_style custom step temp pzz lz f_bias f_bias\[1\] f_bias\[2\] f_bias\[3\] :pre

[Description:]

The fix applies an force to atoms given by the potential

:c,image(Eqs/fix_rhok.jpg)

as described in "(Pedersen)"_#Pedersen. 

This field, that bias configurations with long-range order, 

can be used to study crystal-liquid interfaces

and determine melting temperatures "(Pedersen)"_#Pedersen.

An example of using the interface pinning method 

is located in the folder 

{examples/USER/pinning} of the source code to LAMMPS.

[Restrictions:]

This fix is part of the 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:]

"thermo_style"_thermo_style.html

[Default:] none

:line

:link(Pedersen)

[(Pedersen)] Pedersen, J. Chem. Phys., 139, 104102 (2013).

   fix_reaxc_species

   fix_recenter

   fix_restrain

   fix_rhok

   fix_rigid

   fix_rx

   fix_saed_vtk