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< span id = "index-0" > < / span > < h1 > improper_style ring command< a class = "headerlink" href = "#improper-style-ring-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
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< div class = "section" id = "improper-style-ring-omp-command" >
< h1 > improper_style ring/omp command< a class = "headerlink" href = "#improper-style-ring-omp-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
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< h2 > Syntax< a class = "headerlink" href = "#syntax" title = "Permalink to this headline" > ¶< / a > < / h2 >
< div class = "highlight-python" > < div class = "highlight" > < pre > improper_style ring
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< h2 > Examples< a class = "headerlink" href = "#examples" title = "Permalink to this headline" > ¶< / a > < / h2 >
< div class = "highlight-python" > < div class = "highlight" > < pre > improper_style ring
improper_coeff 1 8000 70.5
< / pre > < / div >
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< div class = "section" id = "description" >
< h2 > Description< a class = "headerlink" href = "#description" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > The < em > ring< / em > improper style uses the potential< / p >
< img alt = "_images/improper_ring.jpg" class = "align-center" src = "_images/improper_ring.jpg" / >
< p > where K is a prefactor, theta is the angle formed by the atoms
specified by (i,j,k,l) indices and theta0 its equilibrium value.< / p >
< p > If the 4 atoms in an improper quadruplet (listed in the data file read
by the < a class = "reference internal" href = "read_data.html" > < em > read_data< / em > < / a > command) are ordered i,j,k,l then
theta_*ijl* is the angle between atoms i,j and l, theta_*ijk* is the
angle between atoms i,j and k, theta_*kjl* is the angle between atoms
j,k, and l.< / p >
< p > The “ ring” improper style implements the improper potential introduced
by Destree et al., in Equation (9) of < a class = "reference internal" href = "#destree" > < span > (Destree)< / span > < / a > . This
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potential does not affect small amplitude vibrations but is used in an
ad-hoc way to prevent the onset of accidentially large amplitude
fluctuations leading to the occurrence of a planar conformation of the
three bonds i-j, j-k and j-l, an intermediate conformation toward the
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chiral inversion of a methine carbon. In the “ Impropers” section of
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data file four atoms: i, j, k and l are specified with i,j and l lying
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on the backbone of the chain and k specifying the chirality of j.< / p >
< p > The following coefficients must be defined for each improper type via
the < a class = "reference internal" href = "improper_coeff.html" > < em > improper_coeff< / em > < / a > command as in the example
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above, or in the data file or restart files read by the
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< a class = "reference internal" href = "read_data.html" > < em > read_data< / em > < / a > or < a class = "reference internal" href = "read_restart.html" > < em > read_restart< / em > < / a >
commands:< / p >
< ul class = "simple" >
< li > K (energy/radian^2)< / li >
< li > theta0 (degrees)< / li >
< / ul >
< p > theta0 is specified in degrees, but LAMMPS converts it to radians
internally; hence the units of K are in energy/radian^2.< / p >
< hr class = "docutils" / >
< p > Styles with a < em > cuda< / em > , < em > gpu< / em > , < em > intel< / em > , < em > kk< / em > , < em > omp< / em > , or < em > opt< / em > suffix are
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functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
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hardware, as discussed in < a class = "reference internal" href = "Section_accelerate.html" > < em > Section_accelerate< / em > < / a >
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of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
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issues.< / p >
< p > These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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enabled if LAMMPS was built with those packages. See the < a class = "reference internal" href = "Section_start.html#start-3" > < span > Making LAMMPS< / span > < / a > section for more info.< / p >
< p > You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the < a class = "reference internal" href = "Section_start.html#start-7" > < span > -suffix command-line switch< / span > < / a > when you invoke LAMMPS, or you can
use the < a class = "reference internal" href = "suffix.html" > < em > suffix< / em > < / a > command in your input script.< / p >
< p > See < a class = "reference internal" href = "Section_accelerate.html" > < em > Section_accelerate< / em > < / a > of the manual for
more instructions on how to use the accelerated styles effectively.< / p >
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< div class = "section" id = "restrictions" >
< h2 > Restrictions< a class = "headerlink" href = "#restrictions" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > This improper style can only be used if LAMMPS was built with the
USER-MISC package. See the < a class = "reference internal" href = "Section_start.html#start-3" > < span > Making LAMMPS< / span > < / a >
section for more info on packages.< / p >
< / div >
< div class = "section" id = "related-commands" >
< h2 > Related commands< a class = "headerlink" href = "#related-commands" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > < a class = "reference internal" href = "improper_coeff.html" > < em > improper_coeff< / em > < / a > < / p >
< p id = "destree" > < strong > (Destree)< / strong > M. Destree, F. Laupretre, A. Lyulin, and J.-P. Ryckaert,
J Chem Phys, 112, 9632 (2000).< / p >
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