forked from lijiext/lammps
99 lines
3.6 KiB
HTML
99 lines
3.6 KiB
HTML
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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</CENTER>
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<HR>
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<H3>fix ipi command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>fix ID group-ID ipi address port [unix]
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
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<LI>ipi = style name of this fix command
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<LI>address = internet address (FQDN or IP), or UNIX socket name
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<LI>port = port number (ignored for UNIX sockets)
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<LI>optional keyword = <I>unix</I>, if present uses a unix socket
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</UL>
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<P><B>Examples:</B>
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</P>
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<P>fix 1 all ipi my.server.com 12345
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fix 1 all ipi mysocket 666 unix
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</P>
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<P><B>Description:</B>
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</P>
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<P>This fix enables LAMMPS to be run as a client for the i-PI Python
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wrapper <A HREF = "#IPI">(IPI)</A> for performing a path integral molecular dynamics
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(PIMD) simulation. The philosophy behind i-PI is described in the
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following publication <A HREF = "#IPICPC">(IPI-CPC)</A>.
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</P>
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<P>A version of the i-PI package, containing only files needed for use
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with LAMMPS, is provided in the tools/i-pi directory. See the
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tools/i-pi/manual.pdf for an introduction to i-PI. The
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examples/USER/i-pi directory contains example scripts for using i-PI
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with LAMMPS.
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</P>
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<P>In brief, the path integral molecular dynamics is performed by the
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Python wrapper, while the client (LAMMPS in this case) simply computes
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forces and energy for each configuration. The communication between
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the two components takes place using sockets, and is reduced to the
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bare minimum. All the parameters of the dynamics are specified in the
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input of i-PI, and all the parameters of the force field must be
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specified as LAMMPS inputs, preceding the <I>fix ipi</I> command.
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</P>
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<P>The server address must be specified by the <I>address</I> argument, and
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can be either the IP address, the fully-qualified name of the server,
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or the name of a UNIX socket for local, faster communication. In the
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case of internet sockets, the <I>port</I> argument specifies the port
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number on which i-PI is listening, while the <I>unix</I> optional switch
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specifies that the socket is a UNIX socket.
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</P>
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<P>Note that there is no check of data integrity, or that the atomic
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configurations make sense. It is assumed that the species in the i-PI
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input are listed in the same order as in the data file of LAMMPS. The
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initial configuration is ignored, as it will be substituted with the
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coordinates received from i-PI before forces are ever evaluated.
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</P>
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<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
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</P>
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<P>There is no restart information associated with this fix, since all
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the dynamical parameters are dealt with by i-PI.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>Using this fix on anything other than all atoms requires particular
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care, since i-PI will know nothing on atoms that are not those whose
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coordinates are transferred. However, one could use this strategy to
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define an external potential acting on the atoms that are moved by
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i-PI.
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</P>
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<P>This fix is part of the USER-MISC package. It is only enabled if
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LAMMPS was built with that package. See the <A HREF = "Section_start.html#start_3">Making
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LAMMPS</A> section for more info. Because of
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the use of UNIX domain sockets, this fix will only work in a UNIX
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environment.
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "fix_nve.html">fix nve</A>
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</P>
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<HR>
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<A NAME = "IPICPC"></A>
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<P><B>(IPI-CPC)</B> Ceriotti, More and Manolopoulos, Comp Phys Comm, 185,
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1019-1026 (2014).
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</P>
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<A NAME = "IPI"></A>
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<P><B>(IPI)</B>
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<A HREF = "http://epfl-cosmo.github.io/gle4md/index.html?page=ipi">http://epfl-cosmo.github.io/gle4md/index.html?page=ipi</A>
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</P>
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</HTML>
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