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txt file with the documentation of the new compute style

doc/src/compute_gyration_shape.txt

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+"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
+
+:link(lws,http://lammps.sandia.gov)
+:link(ld,Manual.html)
+:link(lc,Commands_all.html)
+
+:line
+
+compute gyration/shape command :h3
+
+[Syntax:]
+
+compute ID group-ID gyration computeID :pre
+
+ID, group-ID are documented in "compute"_compute.html command
+gyration/shape = style name of this compute command
+computeID = ID of "compute gyration"_compute_gyration.html command :ul
+
+[Examples:]
+
+compute 1 molecule gyration/shape pe :pre
+
+[Description:]
+
+Define a computation that calculates the eigenvalues of the gyration tensor of a
+group of atoms and three shape parameters. The computation includes all effects 
+due to atoms passing thru periodic boundaries.
+
+The three computed shape parameters are the asphericity, b, the acylindricity, c, 
+and the relative shape anisotropy, k:
+
+:c,image(Eqs/compute_shape_parameters.jpg)
+
+where lx ≤ ly ≤ lz are the three eigenvalues of the gyration tensor.
+The asphericity  is always non-negative and zero only when the three principal 
+moments are equal. This zero condition is met when the distribution of particles 
+is spherically symmetric (hence the name asphericity) but also whenever the particle
+ distribution is symmetric with respect to the three coordinate axes, e.g., 
+when the particles are distributed uniformly on a cube, tetrahedron or other Platonic 
+solid. The acylindricity is always non-negative and zero only when the two principal 
+moments are equal. This zero condition is met when the distribution of particles is 
+cylindrically symmetric (hence the name, acylindricity), but also whenever the particle 
+distribution is symmetric with respect to the two coordinate axes, e.g., when the 
+particles are distributed uniformly on a regular prism. the relative shape anisotropy 
+is bounded between zero (if all points are spherically symmetric) and one 
+(if all points lie on a line).
+
+NOTE: The coordinates of an atom contribute to the gyration tensor in 
+"unwrapped" form, by using the image flags associated with each atom.  
+See the "dump custom"_dump.html command for a discussion of "unwrapped" 
+coordinates. See the Atoms section of the "read_data"_read_data.html 
+command for a discussion of image flags and how they are set for each 
+atom.  You can reset the image flags (e.g. to 0) before invoking this 
+compute by using the "set image"_set.html command.
+
+[Output info:]
+
+This compute calculates a global vector of
+length 6, which can be accessed by indices 1-6. The first three values are the 
+eigenvalues of the gyration tensor followed by the asphericity, the acylindricity
+and the relative shape anisotropy.  The computed values can be used by any command 
+that uses global  vector values from a compute as input.  See the "Howto
+output"_Howto_output.html doc page for an overview of LAMMPS output
+options.
+
+The vector values calculated by this compute are
+"intensive".  The first five vector values will be in
+distance^2 "units"_units.html while the sixth one is dimensionless.
+
+[Restrictions:] 
+
+This compute is part of the USER-MISC package.  It is only enabled if
+LAMMPS was built with that package.  See the "Build
+package"_Build_package.html doc page for more info.
+
+[Related commands:]
+
+"compute gyration"_compute_gyration.html
+
+[Default:] none
+
+:line
+
+:link(Theodorou)
+[(Theodorou)] Theodorou, Suter, Macromolecules, 18, 1206 (1985).
+