forked from lijiext/lammps
108 lines
3.4 KiB
Plaintext
108 lines
3.4 KiB
Plaintext
.. index:: fix ipi
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fix ipi command
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===============
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Syntax
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""""""
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.. parsed-literal::
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fix ID group-ID ipi address port [unix]
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* ID, group-ID are documented in :doc:`fix <fix>` command
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* ipi = style name of this fix command
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* address = internet address (FQDN or IP), or UNIX socket name
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* port = port number (ignored for UNIX sockets)
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* optional keyword = *unix*\ , if present uses a unix socket
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Examples
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""""""""
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fix 1 all ipi my.server.com 12345
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fix 1 all ipi mysocket 666 unix
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Description
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"""""""""""
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This fix enables LAMMPS to be run as a client for the i-PI Python
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wrapper :ref:`(IPI) <IPI>` 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 :ref:`(IPI-CPC) <IPICPC>`.
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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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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 *fix ipi* command.
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The server address must be specified by the *address* 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 *port* argument specifies the port
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number on which i-PI is listening, while the *unix* optional switch
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specifies that the socket is a UNIX socket.
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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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Restart, fix_modify, output, run start/stop, minimize info
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""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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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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Restrictions
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""""""""""""
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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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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 :ref:`Making LAMMPS <start_3>` 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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Related commands
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""""""""""""""""
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:doc:`fix nve <fix_nve>`
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----------
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.. _IPICPC:
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**(IPI-CPC)** Ceriotti, More and Manolopoulos, Comp Phys Comm, 185,
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1019-1026 (2014).
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.. _IPI:
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**(IPI)**
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`http://epfl-cosmo.github.io/gle4md/index.html?page=ipi <http://epfl-cosmo.github.io/gle4md/index.html?page=ipi>`_
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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