forked from lijiext/lammps
80 lines
2.9 KiB
Plaintext
80 lines
2.9 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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temper command :h3
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[Syntax:]
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temper N M temp fix-ID seed1 seed2 index :pre
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N = total # of timesteps to run
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M = attempt a tempering swap every this many steps
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temp = initial temperature for this ensemble
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fix-ID = ID of the fix that will control temperature during the run
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seed1 = random # seed used to decide on adjacent temperature to partner with
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seed2 = random # seed for Boltzmann factor in Metropolis swap
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index = which temperature (0 to N-1) I am simulating (optional) :ul
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[Examples:]
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temper 100000 100 $t tempfix 0 58728
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temper 40000 100 $t tempfix 0 32285 $w :pre
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[Description:]
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Run a parallel tempering (replica exchange) simulation of multiple
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ensembles of a system on multiple partitions of processors. The
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processor partitions are defined using the -partition command-line
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switch (see "this section"_Section_start.html#2_4). Each ensemble's
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temperature is typically controlled at a different value by a fix with
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ID {fix-ID} that controls temperature. Possible fix styles are
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"nvt"_fix_nvt.html, "npt"_fix_npt.html, and
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"temp/rescale"_fix_temp_rescale.html. The desired temperature is
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specified by {temp}, which is typically a variable previously set in
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the input script, so that each partition is assigned a different
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temperature. See the "variable"_variable.html command for more
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details. For example,
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variable t world 300.0 310.0 320.0 330.0 :pre
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As the tempering simulation runs for {N} timesteps, a swap between
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adjacent ensembles will be attempted every {M} timesteps. If {seed1}
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is 0, then the swap attempts will alternate between odd and even
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pairings. If {seed1} is non-zero then it is used as a seed in a
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random number generator to randomly choose an odd or even pairing each
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time. Each attempted swap of temperatures is either accepted or
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rejected based on a Boltzmann-weighted Metropolis criterion which uses
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{seed2} in the random number generator.
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The last argument {index} is optional and is used when restarting a
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tempering run from a set of restart files (one for each replica) which
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had previously swapped to new temperatures. The {index} value (from 0
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to N-1, where N is the # of replicas) identifies which temperature the
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replica was simulating on the timestep the restart files were written.
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Obviously, this argument must be a variable so that each partition has
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the correct value. Set the variable to the {N} values listed in the
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log file for the previous run for the replica temperatures at that
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timestep. For example if the log file listed
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500000 2 4 0 1 3 :pre
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then a setting of
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variable w proc 2 4 0 1 3 :pre
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would be used to restart the run with a tempering command like the
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example above with $w as the last argument.
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[Restrictions:] none
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[Related commands:]
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"variable"_variable.html
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[Default:] none
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