200 lines
8.1 KiB
Plaintext
200 lines
8.1 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,Commands_all.html)
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:line
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fix eos/table/rx command :h3
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fix eos/table/rx/kk command :h3
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[Syntax:]
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fix ID group-ID eos/table/rx style file1 N keyword ... :pre
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ID, group-ID are documented in "fix"_fix.html command
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eos/table/rx = style name of this fix command
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style = {linear} = method of interpolation
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file1 = filename containing the tabulated equation of state
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N = use N values in {linear} tables
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keyword = name of table keyword corresponding to table file
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file2 = filename containing the heats of formation of each species (optional)
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deltaHf = heat of formation for a single species in energy units (optional)
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energyCorr = energy correction in energy units (optional)
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tempCorrCoeff = temperature correction coefficient (optional) :ul
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[Examples:]
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fix 1 all eos/table/rx linear eos.table 10000 KEYWORD thermo.table
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fix 1 all eos/table/rx linear eos.table 10000 KEYWORD 1.5
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fix 1 all eos/table/rx linear eos.table 10000 KEYWORD 1.5 0.025 0.0 :pre
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[Description:]
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Fix {eos/table/rx} applies a tabulated mesoparticle equation
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of state to relate the concentration-dependent particle internal
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energy (u_i) to the particle internal temperature (dpdTheta_i).
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The concentration-dependent particle internal energy (u_i) is
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computed according to the following relation:
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:c,image(Eqs/fix_eos_table_rx.jpg)
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where {m} is the number of species, {c_i,j} is the concentration of
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species {j} in particle {i}, {u_j} is the internal energy of species j,
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{DeltaH_f,j} is the heat of formation of species {j}, N is the number of
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molecules represented by the coarse-grained particle, kb is the
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Boltzmann constant, and T is the temperature of the system. Additionally,
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it is possible to modify the concentration-dependent particle internal
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energy relation by adding an energy correction, temperature-dependent
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correction, and/or a molecule-dependent correction. An energy correction can
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be specified as a constant (in energy units). A temperature correction can be
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specified by multiplying a temperature correction coefficient by the
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internal temperature. A molecular correction can be specified by
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by multiplying a molecule correction coefficient by the average number of
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product gas particles in the coarse-grain particle.
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Fix {eos/table/rx} creates interpolation tables of length {N} from {m}
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internal energy values of each species {u_j} listed in a file as a
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function of internal temperature. During a simulation, these tables
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are used to interpolate internal energy or temperature values as needed.
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The interpolation is done with the {linear} style. For the {linear} style,
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the internal temperature is used to find 2 surrounding table values from
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which an internal energy is computed by linear interpolation. A secant
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solver is used to determine the internal temperature from the internal energy.
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The first filename specifies a file containing tabulated internal
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temperature and {m} internal energy values for each species {u_j}.
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The keyword specifies a section of the file. The format of this
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file is described below.
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The second filename specifies a file containing heat of formation
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{DeltaH_f,j} for each species.
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In cases where the coarse-grain particle represents a single molecular
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species (i.e., no reactions occur and fix {rx} is not present in the input file),
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fix {eos/table/rx} can be applied in a similar manner to fix {eos/table}
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within a non-reactive DPD simulation. In this case, the heat of formation
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filename is replaced with the heat of formation value for the single species.
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Additionally, the energy correction and temperature correction coefficients may
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also be specified as fix arguments.
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:line
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The format of a tabulated file is as follows (without the
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parenthesized comments):
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# EOS TABLE (one or more comment or blank lines) :pre
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KEYWORD (keyword is first text on line)
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N 500 h2 no2 n2 ... no (N parameter species1 species2 ... speciesN)
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(blank)
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1 1.00 0.000 ... 0.0000 (index, internal temperature, internal energy of species 1, ..., internal energy of species m)
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2 1.02 0.001 ... 0.0002
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...
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500 10.0 0.500 ... 1.0000 :pre
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A section begins with a non-blank line whose 1st character is not a
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"#"; blank lines or lines starting with "#" can be used as comments
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between sections. The first line begins with a keyword which
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identifies the section. The line can contain additional text, but the
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initial text must match the argument specified in the fix command.
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The next line lists the number of table entries and the species names
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that correspond with all the species listed in the reaction equations
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through the {fix rx} command.
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The parameter "N" is required and its value is the number of table
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entries that follow. Let Nfile = "N" in the tabulated file.
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What LAMMPS does is a preliminary interpolation by creating splines
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using the Nfile tabulated values as nodal points.
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Following a blank line, the next N lines list the tabulated values.
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On each line, the 1st value is the index from 1 to N, the 2nd value is
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the internal temperature (in temperature units), the 3rd value until
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the {m+3} value are the internal energies of the m species (in energy units).
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Note that all internal temperature and internal energy values must
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increase from one line to the next.
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Note that one file can contain many sections, each with a tabulated
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potential. LAMMPS reads the file section by section until it finds
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one that matches the specified keyword.
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:line
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The format of a heat of formation file is as follows (without the
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parenthesized comments):
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# HEAT OF FORMATION TABLE (one or more comment or blank lines) :pre
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(blank)
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h2 0.00 (species name, heat of formation)
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no2 0.34
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n2 0.00
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...
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no 0.93 :pre
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Note that the species can be listed in any order. The tag that is
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used as the species name must correspond with the tags used to define
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the reactions with the "fix rx"_fix_rx.html command.
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Alternatively, corrections to the EOS can be included by specifying
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three additional columns that correspond to the energy correction,
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the temperature correction coefficient and molecule correction
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coefficient. In this case, the format of the file is as follows:
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# HEAT OF FORMATION TABLE (one or more comment or blank lines) :pre
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(blank)
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h2 0.00 1.23 0.025 0.0 (species name, heat of formation, energy correction, temperature correction coefficient, molecule correction coefficient)
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no2 0.34 0.00 0.000 -1.76
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n2 0.00 0.00 0.000 -1.76
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...
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no 0.93 0.00 0.000 -1.76 :pre
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:line
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Styles with a {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed on the "Speed packages"_Speed_packages.html doc
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page. The accelerated styles take the same arguments and should
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produce the same results, except for round-off and precision issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the "Build
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package"_Build_package.html doc page for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the "-suffix command-line
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switch"_Run_options.html when you invoke LAMMPS, or you can use the
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"suffix"_suffix.html command in your input script.
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See the "Speed packages"_Speed_packages.html doc page for more
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instructions on how to use the accelerated styles effectively.
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:line
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[Restrictions:]
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This command is part of the USER-DPD package. It is only enabled if
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LAMMPS was built with that package. See the "Build
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package"_Build_package.html doc page for more info.
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This command also requires use of the "atom_style dpd"_atom_style.html
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command.
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The equation of state must be a monotonically increasing function.
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An error will occur if the internal temperature or internal energies
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are not within the table cutoffs.
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[Related commands:]
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"fix rx"_fix_rx.html,
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"pair dpd/fdt"_pair_dpd_fdt.html
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[Default:] none
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:line
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