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	<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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	<HR>

	<H3>read_data command
	</H3>
	<P><B>Syntax:</B>
	</P>
	<PRE>read_data file keyword args ...
	</PRE>
	<UL><LI>file = name of data file to read in

	<LI>zero or more keyword/arg pairs may be appended

	<LI>keyword = <I>add</I> or <I>offset</I> or <I>shift</I> or <I>extra/atom/types</I> or <I>extra/bond/types</I> or <I>extra/angle/types</I> or <I>extra/dihedral/types</I> or <I>extra/improper/types</I> or <I>group</I> or <I>fix</I>

	<PRE> <I>add</I> arg = <I>append</I> or <I>Nstart</I> or <I>merge</I>
	append = add new atoms with IDs appended to current IDs
	Nstart = add new atoms with IDs starting with Nstart
	merge = add new atoms with their IDs unchanged
	<I>offset</I> args = toff boff aoff doff ioff
	toff = offset to add to atom types
	boff = offset to add to bond types
	aoff = offset to add to angle types
	doff = offset to add to dihedral types
	ioff = offset to add to improper types
	<I>shift</I> args = Sx Sy Sz
	Sx,Sy,Sz = distance to shift atoms when adding to system (distance units)
	<I>extra/atom/types</I> arg = # of extra atom types
	<I>extra/bond/types</I> arg = # of extra bond types
	<I>extra/angle/types</I> arg = # of extra angle types
	<I>extra/dihedral/types</I> arg = # of extra dihedral types
	<I>extra/improper/types</I> arg = # of extra improper types
	<I>group</I> args = groupID
	groupID = add atoms in data file to this group
	<I>fix</I> args = fix-ID header-string section-string
	fix-ID = ID of fix to process header lines and sections of data file
	header-string = header lines containing this string will be passed to fix
	section-string = section names with this string will be passed to fix
	</PRE>

	</UL>
	<P><B>Examples:</B>
	</P>
	<PRE>read_data data.lj
	read_data ../run7/data.polymer.gz
	read_data data.protein fix mycmap crossterm CMAP
	read_data data.water add append offset 3 1 1 1 1 shift 0.0 0.0 50.0
	read_data data.water add merge 1 group solvent
	</PRE>
	<P><B>Description:</B>
	</P>
	<P>Read in a data file containing information LAMMPS needs to run a
	simulation. The file can be ASCII text or a gzipped text file
	(detected by a .gz suffix). This is one of 3 ways to specify initial
	atom coordinates; see the <A HREF = "read_restart.html">read_restart</A> and
	<A HREF = "create_atoms.html">create_atoms</A> commands for alternative methods.
	Also see the explanation of the <A HREF = "Section_start.html#start_7">-restart command-line
	switch</A> which can convert a restart file to
	a data file.
	</P>
	<P>This command can be used multiple times to add new atoms and their
	properties to an existing system by using the <I>add</I>, <I>offset</I>, and
	<I>shift</I> keywords. See more details below, which includes the use case
	for the <I>extra</I> keywords.
	</P>
	<P>The <I>group</I> keyword adds all the atoms in the data file to the
	specified group-ID. The group will be created if it does not already
	exist. This is useful if you are reading multiple data files and wish
	to put sets of atoms into different groups so they can be operated on
	later. E.g. a group of added atoms can be moved to new positions via
	the <A HREF = "displace_atoms.html">displace_atoms</A> command. Note that atoms
	read from the data file are also always added to the "all" group. The
	<A HREF = "group.html">group</A> command discusses atom groups, as used in LAMMPS.
	</P>
	<P>The use of the <I>fix</I> keyword is discussed below.
	</P>
	<HR>

	<P><B>Reading multiple data files</B>
	</P>
	<P>The read_data command can be used multiple times with the same or
	different data files to build up a complex system from components
	contained in individual data files. For example one data file could
	contain fluid in a confined domain; a second could contain wall atoms,
	and the second file could be read a third time to create a wall on the
	other side of the fluid. The third set of atoms could be rotated to
	an opposing direction using the <A HREF = "displace_atoms.html">displace_atoms</A>
	command, after the third read_data command is used.
	</P>
	<P>The <I>add</I>, <I>offset</I>, <I>shift</I>, <I>extra</I>, and <I>group</I> keywords are
	useful in this context.
	</P>
	<P>If a simulation box does not yet exist, the <I>add</I> keyword
	cannot be used; the read_data command is being used for the first
	time. If a simulation box does exist, due to using the
	<A HREF = "create_box.html">create_box</A> command, or a previous read_data command,
	then the <I>add</I> keyword must be used.
	</P>
	<P>IMPORTANT NOTE: The simulation box size (xlo to xhi, ylo to yhi, zlo
	to zhi) in the new data file will be merged with the existing
	simulation box to create a large enough box in each dimension to
	contain both the existing and new atoms. Each box dimension never
	shrinks due to this merge operation, it only stays the same or
	grows. Care must be used if you are growing the existing simulation
	box in a periodic dimension. If there are existing atoms with bonds
	that straddle that periodic boundary, then the atoms may become far
	apart if the box size grows. This will separate the atoms in the
	bond, which can lead to "lost" bond atoms or bad dynamics.
	</P>
	<P>The three choices for the <I>add</I> argument affect how the IDs of atoms
	in the data file are treated. If <I>append</I> is specified, atoms in the
	data file are added to the current system, with their atom IDs reset
	so that an atomID = M in the data file becomes atomID = N+M, where N
	is the largest atom ID in the current system. This rule is applied to
	all occurrences of atom IDs in the data file, e.g. in the Velocity or
	Bonds section. If <I>Nstart</I> is specified, then <I>Nstart</I> is a numeric
	value is given, e.g. 1000, so that an atomID = M in the data file
	becomes atomID = 1000+M. If <I>merge</I> is specified, the data file atoms
	are added to the current system without changing their IDs. They are
	assumed to merge (without duplication) with the currently defined
	atoms. It is up to you to insure there are no multiply defined atom
	IDs, as LAMMPS only performs an incomplete check that this is the case
	by insuring the resulting max atomID >= the number of atoms.
	</P>
	<P>The <I>offset</I> and <I>shift</I> keywords can only be used if the <I>add</I>
	keyword is also specified.
	</P>
	<P>The <I>offset</I> keyword adds the specified offset values to the atom
	types, bond types, angle types, dihedral types, and improper types as
	they are read from the data file. E.g. if <I>toff</I> = 2, and the file
	uses atom types 1,2,3, then the added atoms will have atom types
	3,4,5. These offsets apply to all occurrences of types in the data
	file, e.g. for the Atoms or Masses or Pair Coeffs or Bond Coeffs
	sections. This makes it easy to use atoms and molecules and their
	attributes from a data file in different simulations, where you want
	their types (atom, bond, angle, etc) to be different depending on what
	other types already exist. All five offset values must be specified,
	but individual values will be ignored if the data file does not use
	that attribute (e.g. no bonds).
	</P>
	<P>The <I>shift</I> keyword can be used to specify an (Sx, Sy, Sz)
	displacement applied to the coordinates of each atom. Sz must be 0.0
	for a 2d simulation. This is a mechanism for adding structured
	collections of atoms at different locations within the simulation box,
	to build up a complex geometry. It is up to you to insure atoms do
	not end up overlapping unphysically which would lead to bad dynamics.
	Note that the <A HREF = "displace_atoms.html">displace_atoms</A> command can be used
	to move a subset of atoms after they have been read from a data file.
	Likewise, the <A HREF = "delete_atoms.html">delete_atoms</A> command can be used to
	remove overlapping atoms. Note that the shift values (Sx, Sy, Sz) are
	also added to the simulation box information (xlo, xhi, ylo, yhi, zlo,
	zhi) in the data file to shift its boundaries. E.g. xlo_new = xlo +
	Sx, xhi_new = xhi + Sx.
	</P>
	<P>The <I>extra</I> keywords can only be used the first time the read_data
	command is used. They are useful if you intend to add new atom, bond,
	angle, etc types later with additional read_data commands. This is
	because the maximum number of allowed atom, bond, angle, etc types is
	set by LAMMPS when the system is first initialized. If you do not use
	the <I>extra</I> keywords, then the number of these types will be limited
	to what appears in the first data file you read. For example, if the
	first data file is a solid substrate of Si, it will likely specify a
	single atom type. If you read a second data file with a different
	material (water molecules) that sit on top of the substrate, you will
	want to use different atom types for those atoms. You can only do
	this if you set the <I>extra/atom/types</I> keyword to a sufficiently large
	value when reading the substrate data file. Note that use of the
	<I>extra</I> keywords also allows each data file to contain sections like
	Masses or Pair Coeffs or Bond Coeffs which are sized appropriately for
	the number of types in that data file. If the <I>offset</I> keyword is
	used appropriately when each data file is read, the values in those
	sections will be stored correctly in the larger data structures
	allocated by the use of the <I>extra</I> keywords. E.g. the substrate file
	can list mass and pair coefficients for type 1 silicon atoms. The
	water file can list mass and pair coeffcients for type 1 and type 2
	hydrogen and oxygen atoms. Use of the <I>extra</I> and <I>offset</I> keywords
	will store those mass and pair coefficient values appropriately in
	data structures that allow for 3 atom types (Si, H, O). Of course,
	you would still need to specify coefficients for H/Si and O/Si
	interactions in your input script to have a complete pairwise
	interaction model.
	</P>
	<P>An alternative to using the <I>extra</I> keywords with the read_data
	command, is to use the <A HREF = "create_box.html">create_box</A> command to
	initialize the simulation box and all the various type limits you need
	via its <I>extra</I> keywords. Then use the read_data command one or more
	times to populate the system with atoms, bonds, angles, etc, using the
	<I>offset</I> keyword if desired to alter types used in the various data
	files you read.
	</P>
	<HR>

	<P><B>Format of a data file</B>
	</P>
	<P>The structure of the data file is important, though many settings and
	sections are optional or can come in any order. See the examples
	directory for sample data files for different problems.
	</P>
	<P>A data file has a header and a body. The header appears first. The
	first line of the header is always skipped; it typically contains a
	description of the file. Then lines are read one at a time. Lines
	can have a trailing comment starting with '#' that is ignored. If the
	line is blank (only whitespace after comment is deleted), it is
	skipped. If the line contains a header keyword, the corresponding
	value(s) is read from the line. If it doesn't contain a header
	keyword, the line begins the body of the file.
	</P>
	<P>The body of the file contains zero or more sections. The first line
	of a section has only a keyword. This line can have a trailing
	comment starting with '#' that is either ignored or can be used to
	check for a style match, as described below. The next line is
	skipped. The remaining lines of the section contain values. The
	number of lines depends on the section keyword as described below.
	Zero or more blank lines can be used between sections. Sections can
	appear in any order, with a few exceptions as noted below.
	</P>
	<P>The keyword <I>fix</I> can be used one or more times. Each usage specifies
	a fix that will be used to process a specific portion of the data
	file. Any header line containing <I>header-string</I> and any section with
	a name containing <I>section-string</I> will be passed to the specified
	fix. See the <A HREF = "fix_property_atom.html">fix property/atom</A> command for
	an example of a fix that operates in this manner. The doc page for
	the fix defines the syntax of the header line(s) and section(s) that
	it reads from the data file. Note that the <I>header-string</I> can be
	specified as NULL, in which case no header lines are passed to the
	fix. This means that it can infer the length of its Section from
	standard header settings, such as the number of atoms.
	</P>
	<P>The formatting of individual lines in the data file (indentation,
	spacing between words and numbers) is not important except that header
	and section keywords (e.g. atoms, xlo xhi, Masses, Bond Coeffs) must
	be capitalized as shown and can't have extra white space between their
	words - e.g. two spaces or a tab between the 2 words in "xlo xhi" or
	the 2 words in "Bond Coeffs", is not valid.
	</P>
	<HR>

	<P><B>Format of the header of a data file</B>
	</P>
	<P>These are the recognized header keywords. Header lines can come in
	any order. The value(s) are read from the beginning of the line.
	Thus the keyword <I>atoms</I> should be in a line like "1000 atoms"; the
	keyword <I>ylo yhi</I> should be in a line like "-10.0 10.0 ylo yhi"; the
	keyword <I>xy xz yz</I> should be in a line like "0.0 5.0 6.0 xy xz yz".
	All these settings have a default value of 0, except the lo/hi box
	size defaults are -0.5 and 0.5. A line need only appear if the value
	is different than the default.
	</P>
	<UL><LI><I>atoms</I> = # of atoms in system
	<LI><I>bonds</I> = # of bonds in system
	<LI><I>angles</I> = # of angles in system
	<LI><I>dihedrals</I> = # of dihedrals in system
	<LI><I>impropers</I> = # of impropers in system
	<LI><I>atom types</I> = # of atom types in system
	<LI><I>bond types</I> = # of bond types in system
	<LI><I>angle types</I> = # of angle types in system
	<LI><I>dihedral types</I> = # of dihedral types in system
	<LI><I>improper types</I> = # of improper types in system
	<LI><I>extra bond per atom</I> = leave space for this many new bonds per atom
	<LI><I>extra angle per atom</I> = leave space for this many new angles per atom
	<LI><I>extra dihedral per atom</I> = leave space for this many new dihedrals per atom
	<LI><I>extra improper per atom</I> = leave space for this many new impropers per atom
	<LI><I>extra special per atom</I> = leave space for this many new special bonds per atom
	<LI><I>ellipsoids</I> = # of ellipsoids in system
	<LI><I>lines</I> = # of line segments in system
	<LI><I>triangles</I> = # of triangles in system
	<LI><I>bodies</I> = # of bodies in system
	<LI><I>xlo xhi</I> = simulation box boundaries in x dimension
	<LI><I>ylo yhi</I> = simulation box boundaries in y dimension
	<LI><I>zlo zhi</I> = simulation box boundaries in z dimension
	<LI><I>xy xz yz</I> = simulation box tilt factors for triclinic system
	</UL>
	<P>The initial simulation box size is determined by the lo/hi settings.
	In any dimension, the system may be periodic or non-periodic; see the
	<A HREF = "boundary.html">boundary</A> command. When the simulation box is created
	it is also partitioned into a regular 3d grid of rectangular bricks,
	one per processor, based on the number of processors being used and
	the settings of the <A HREF = "processors.html">processors</A> command. The
	partitioning can later be changed by the <A HREF = "balance.html">balance</A> or
	<A HREF = "fix_balance.html">fix balance</A> commands.
	</P>
	<P>If the <I>xy xz yz</I> line does not appear, LAMMPS will set up an
	axis-aligned (orthogonal) simulation box. If the line does appear,
	LAMMPS creates a non-orthogonal simulation domain shaped as a
	parallelepiped with triclinic symmetry. The parallelepiped has its
	"origin" at (xlo,ylo,zlo) and is defined by 3 edge vectors starting
	from the origin given by A = (xhi-xlo,0,0); B = (xy,yhi-ylo,0); C =
	(xz,yz,zhi-zlo). <I>Xy,xz,yz</I> can be 0.0 or positive or negative values
	and are called "tilt factors" because they are the amount of
	displacement applied to faces of an originally orthogonal box to
	transform it into the parallelepiped.
	</P>
	<P>By default, the tilt factors (xy,xz,yz) can not skew the box more than
	half the distance of the corresponding parallel box length. For
	example, if xlo = 2 and xhi = 12, then the x box length is 10 and the
	xy tilt factor must be between -5 and 5. Similarly, both xz and yz
	must be between -(xhi-xlo)/2 and +(yhi-ylo)/2. Note that this is not
	a limitation, since if the maximum tilt factor is 5 (as in this
	example), then configurations with tilt = ..., -15, -5, 5, 15, 25,
	... are all geometrically equivalent. If you wish to define a box
	with tilt factors that exceed these limits, you can use the <A HREF = "box.html">box
	tilt</A> command, with a setting of <I>large</I>; a setting of
	<I>small</I> is the default.
	</P>
	<P>See <A HREF = "Section_howto.html#howto_12">Section_howto 12</A> of the doc pages
	for a geometric description of triclinic boxes, as defined by LAMMPS,
	and how to transform these parameters to and from other commonly used
	triclinic representations.
	</P>
	<P>When a triclinic system is used, the simulation domain should normally
	be periodic in the dimension that the tilt is applied to, which is
	given by the second dimension of the tilt factor (e.g. y for xy tilt).
	This is so that pairs of atoms interacting across that boundary will
	have one of them shifted by the tilt factor. Periodicity is set by
	the <A HREF = "boundary.html">boundary</A> command. For example, if the xy tilt
	factor is non-zero, then the y dimension should be periodic.
	Similarly, the z dimension should be periodic if xz or yz is non-zero.
	LAMMPS does not require this periodicity, but you may lose atoms if
	this is not the case.
	</P>
	<P>Also note that if your simulation will tilt the box, e.g. via the <A HREF = "fix_deform.html">fix
	deform</A> command, the simulation box must be setup to
	be triclinic, even if the tilt factors are initially 0.0. You can
	also change an orthogonal box to a triclinic box or vice versa by
	using the <A HREF = "change_box.html">change box</A> command with its <I>ortho</I> and
	<I>triclinic</I> options.
	</P>
	<P>For 2d simulations, the <I>zlo zhi</I> values should be set to bound the z
	coords for atoms that appear in the file; the default of -0.5 0.5 is
	valid if all z coords are 0.0. For 2d triclinic simulations, the xz
	and yz tilt factors must be 0.0.
	</P>
	<P>If the system is periodic (in a dimension), then atom coordinates can
	be outside the bounds (in that dimension); they will be remapped (in a
	periodic sense) back inside the box. Note that if the <I>add</I> option is
	being used to add atoms to a simulation box that already exists, this
	periodic remapping will be performed using simulation box bounds that
	are the union of the existing box and the box boundaries in the new
	data file.
	</P>
	<P>IMPORTANT NOTE: If the system is non-periodic (in a dimension), then
	all atoms in the data file must have coordinates (in that dimension)
	that are "greater than or equal to" the lo value and "less than or
	equal to" the hi value. If the non-periodic dimension is of style
	"fixed" (see the <A HREF = "boundary.html">boundary</A> command), then the atom
	coords must be strictly "less than" the hi value, due to the way
	LAMMPS assign atoms to processors. Note that you should not make the
	lo/hi values radically smaller/larger than the extent of the atoms.
	For example, if your atoms extend from 0 to 50, you should not specify
	the box bounds as -10000 and 10000. This is because LAMMPS uses the
	specified box size to layout the 3d grid of processors. A huge
	(mostly empty) box will be sub-optimal for performance when using
	"fixed" boundary conditions (see the <A HREF = "boundary.html">boundary</A>
	command). When using "shrink-wrap" boundary conditions (see the
	<A HREF = "boundary.html">boundary</A> command), a huge (mostly empty) box may cause
	a parallel simulation to lose atoms when LAMMPS shrink-wraps the box
	around the atoms. The read_data command will generate an error
	in this case.
	</P>
	<P>The "extra bond per atom" setting (angle, dihedral, improper) is only
	needed if new bonds (angles, dihedrals, impropers) will be added to
	the system when a simulation runs, e.g. by using the <A HREF = "fix_bond_create.html">fix
	bond/create</A> command. This will pre-allocate
	space in LAMMPS data structures for storing the new bonds (angles,
	dihedrals, impropers).
	</P>
	<P>The "extra special per atom" setting is typically only needed if new
	bonds/angles/etc will be added to the system, e.g. by using the <A HREF = "fix_bond_create.html">fix
	bond/create</A> command. Or if entire new molecules
	will be added to the system, e.g. by using the <A HREF = "fix_deposit.html">fix
	deposit</A> or <A HREF = "fix_pour.html">fix pour</A> commands, which
	will have more special 1-2,1-3,1-4 neighbors than any other molecules
	defined in the data file. Using this setting will pre-allocate space
	in the LAMMPS data structures for storing these neighbors. See the
	<A HREF = "special_bonds.html">special_bonds</A> and <A HREF = "molecule.html">molecule</A> doc
	pages for more discussion of 1-2,1-3,1-4 neighbors.
	</P>
	<P>IMPORTANT NOTE: All of the "extra" settings are only used if they
	appear in the first data file read; see the description of the <I>add</I>
	keyword above for reading multiple data files. If they appear in
	later data files, they are ignored.
	</P>
	<P>The "ellipsoids" and "lines" and "triangles" and "bodies" settings are
	only used with <A HREF = "atom_style.html">atom_style ellipsoid or line or tri or
	body</A> and specify how many of the atoms are
	finite-size ellipsoids or lines or triangles or bodies; the remainder
	are point particles. See the discussion of ellipsoidflag and the
	<I>Ellipsoids</I> section below. See the discussion of lineflag and the
	<I>Lines</I> section below. See the discussion of triangleflag and the
	<I>Triangles</I> section below. See the discussion of bodyflag and the
	<I>Bodies</I> section below.
	</P>
	<P>IMPORTANT NOTE: For <A HREF = "atom_style.html">atom_style template</A>, the
	molecular topology (bonds,angles,etc) is contained in the molecule
	templates read-in by the <A HREF = "molecule.html">molecule</A> command. This means
	you cannot set the <I>bonds</I>, <I>angles</I>, etc header keywords in the data
	file, nor can you define <I>Bonds</I>, <I>Angles</I>, etc sections as discussed
	below. You can set the <I>bond types</I>, <I>angle types</I>, etc header
	keywords, though it is not necessary. If specified, they must match
	the maximum values defined in any of the template molecules.
	</P>
	<HR>

	<P><B>Format of the body of a data file</B>
	</P>
	<P>These are the section keywords for the body of the file.
	</P>
	<UL><LI><I>Atoms, Velocities, Masses, Ellipsoids, Lines, Triangles, Bodies</I> = atom-property sections
	<LI><I>Bonds, Angles, Dihedrals, Impropers</I> = molecular topology sections
	<LI><I>Pair Coeffs, PairIJ Coeffs, Bond Coeffs, Angle Coeffs, Dihedral Coeffs, Improper Coeffs</I> = force field sections
	<LI><I>BondBond Coeffs, BondAngle Coeffs, MiddleBondTorsion Coeffs, EndBondTorsion Coeffs, AngleTorsion Coeffs, AngleAngleTorsion Coeffs, BondBond13 Coeffs, AngleAngle Coeffs</I> = class 2 force field sections
	</UL>
	<P>These keywords will check an appended comment for a match with the
	currently defined style:
	</P>
	<UL><LI><I>Atoms, Pair Coeffs, PairIJ Coeffs, Bond Coeffs, Angle Coeffs, Dihedral Coeffs, Improper Coeffs</I>
	</UL>
	<P>For example, these lines:
	</P>
	<PRE>Atoms # sphere
	Pair Coeffs # lj/cut
	</PRE>
	<P>will check if the currently-defined <A HREF = "atom_style.html">atom_style</A> is
	<I>sphere</I>, and the current <A HREF = "pair_style">pair_style</A> is <I>lj/cut</I>. If
	not, LAMMPS will issue a warning to indicate that the data file
	section likely does not contain the correct number or type of
	parameters expected for the currently-defined style.
	</P>
	<P>Each section is listed below in alphabetic order. The format of each
	section is described including the number of lines it must contain and
	rules (if any) for where it can appear in the data file.
	</P>
	<P>Any individual line in the various sections can have a trailing
	comment starting with "#" for annotation purposes. E.g. in the
	Atoms section:
	</P>
	<PRE>10 1 17 -1.0 10.0 5.0 6.0 # salt ion
	</PRE>
	<HR>

	<P><I>Angle Coeffs</I> section:
	</P>
	<UL><LI>one line per angle type

	<LI>line syntax: ID coeffs

	<PRE> ID = angle type (1-N)
	coeffs = list of coeffs
	</PRE>
	<LI>example:

	<PRE> 6 70 108.5 0 0
	</PRE>

	</UL>
	<P>The number and meaning of the coefficients are specific to the defined
	angle style. See the <A HREF = "angle_style.html">angle_style</A> and
	<A HREF = "angle_coeff.html">angle_coeff</A> commands for details. Coefficients can
	also be set via the <A HREF = "angle_coeff.html">angle_coeff</A> command in the
	input script.
	</P>
	<HR>

	<P><I>AngleAngle Coeffs</I> section:
	</P>
	<UL><LI>one line per improper type

	<LI>line syntax: ID coeffs

	<PRE> ID = improper type (1-N)
	coeffs = list of coeffs (see <A HREF = "improper_coeff.html">improper_coeff</A>)
	</PRE>

	</UL>
	<HR>

	<P><I>AngleAngleTorsion Coeffs</I> section:
	</P>
	<UL><LI>one line per dihedral type

	<LI>line syntax: ID coeffs

	<PRE> ID = dihedral type (1-N)
	coeffs = list of coeffs (see <A HREF = "dihedral_coeff.html">dihedral_coeff</A>)
	</PRE>

	</UL>
	<HR>

	<P><I>Angles</I> section:
	</P>
	<UL><LI>one line per angle

	<LI>line syntax: ID type atom1 atom2 atom3

	<PRE> ID = number of angle (1-Nangles)
	type = angle type (1-Nangletype)
	atom1,atom2,atom3 = IDs of 1st,2nd,3rd atoms in angle
	</PRE>
	example:
	<BR>
	<PRE> 2 2 17 29 430
	</PRE>

	</UL>
	<P>The 3 atoms are ordered linearly within the angle. Thus the central
	atom (around which the angle is computed) is the atom2 in the list.
	E.g. H,O,H for a water molecule. The <I>Angles</I> section must appear
	after the <I>Atoms</I> section. All values in this section must be
	integers (1, not 1.0).
	</P>
	<HR>

	<P><I>AngleTorsion Coeffs</I> section:
	</P>
	<UL><LI>one line per dihedral type

	<LI>line syntax: ID coeffs

	<PRE> ID = dihedral type (1-N)
	coeffs = list of coeffs (see <A HREF = "dihedral_coeff.html">dihedral_coeff</A>)
	</PRE>

	</UL>
	<HR>

	<P><I>Atoms</I> section:
	</P>
	<UL><LI>one line per atom
	<LI>line syntax: depends on atom style
	</UL>
	<P>An <I>Atoms</I> section must appear in the data file if natoms > 0 in the
	header section. The atoms can be listed in any order. These are the
	line formats for each <A HREF = "atom_style.html">atom style</A> in LAMMPS. As
	discussed below, each line can optionally have 3 flags (nx,ny,nz)
	appended to it, which indicate which image of a periodic simulation
	box the atom is in. These may be important to include for some kinds
	of analysis.
	</P>
	<DIV ALIGN=center><TABLE BORDER=1 >
	<TR><TD >angle</TD><TD > atom-ID molecule-ID atom-type x y z</TD></TR>
	<TR><TD >atomic</TD><TD > atom-ID atom-type x y z</TD></TR>
	<TR><TD >body</TD><TD > atom-ID atom-type bodyflag mass x y z</TD></TR>
	<TR><TD >bond</TD><TD > atom-ID molecule-ID atom-type x y z</TD></TR>
	<TR><TD >charge</TD><TD > atom-ID atom-type q x y z</TD></TR>
	<TR><TD >dipole</TD><TD > atom-ID atom-type q x y z mux muy muz</TD></TR>
	<TR><TD >electron</TD><TD > atom-ID atom-type q spin eradius x y z</TD></TR>
	<TR><TD >ellipsoid</TD><TD > atom-ID atom-type ellipsoidflag density x y z</TD></TR>
	<TR><TD >full</TD><TD > atom-ID molecule-ID atom-type q x y z</TD></TR>
	<TR><TD >line</TD><TD > atom-ID molecule-ID atom-type lineflag density x y z</TD></TR>
	<TR><TD >meso</TD><TD > atom-ID atom-type rho e cv x y z</TD></TR>
	<TR><TD >molecular</TD><TD > atom-ID molecule-ID atom-type x y z</TD></TR>
	<TR><TD >peri</TD><TD > atom-ID atom-type volume density x y z</TD></TR>
	<TR><TD >smd</TD><TD > atom-ID atom-type molecule volume mass kernel_radius contact_radius x y z</TD></TR>
	<TR><TD >sphere</TD><TD > atom-ID atom-type diameter density x y z</TD></TR>
	<TR><TD >template</TD><TD > atom-ID molecule-ID template-index template-atom atom-type x y z</TD></TR>
	<TR><TD >tri</TD><TD > atom-ID molecule-ID atom-type triangleflag density x y z</TD></TR>
	<TR><TD >wavepacket</TD><TD > atom-ID atom-type charge spin eradius etag cs_re cs_im x y z</TD></TR>
	<TR><TD >hybrid</TD><TD > atom-ID atom-type x y z sub-style1 sub-style2 ...
	</TD></TR></TABLE></DIV>

	<P>The keywords have these meanings:
	</P>
	<UL><LI>atom-ID = integer ID of atom
	<LI>molecule-ID = integer ID of molecule the atom belongs to
	<LI>atom-type = type of atom (1-Ntype)
	<LI>q = charge on atom (charge units)
	<LI>diameter = diameter of spherical atom (distance units)
	<LI>ellipsoidflag = 1 for ellipsoidal particles, 0 for point particles
	<LI>lineflag = 1 for line segment particles, 0 for point particles
	<LI>triangleflag = 1 for triangular particles, 0 for point particles
	<LI>bodyflag = 1 for body particles, 0 for point particles
	<LI>template-index = which molecule within the molecule template the atom is part of
	<LI>template-atom = which atom within a template molecule the atom is
	<LI>density = density of particle (mass/distance^3 or mass/distance^2 or mass/distance units, depending on dimensionality of particle)
	<LI>mass = mass of particle (mass units)
	<LI>volume = volume of particle (distance^3 units)
	<LI>x,y,z = coordinates of atom
	<LI>mux,muy,muz = components of dipole moment of atom (dipole units)
	<LI>rho = density (need units) for SPH particles
	<LI>e = energy (need units) for SPH particles
	<LI>cv = heat capacity (need units) for SPH particles
	<LI>spin = electron spin (+1/-1), 0 = nuclei, 2 = fixed-core, 3 = pseudo-cores (i.e. ECP)
	<LI>eradius = electron radius (or fixed-core radius)
	<LI>etag = integer ID of electron that each wavepacket belongs to
	<LI>cs_re,cs_im = real/imaginary parts of wavepacket coefficients
	<LI>kernel_radius = ??? (distance units)
	<LI>contact_radius = ??? (distance units)
	</UL>
	<P>The units for these quantities depend on the unit style; see the
	<A HREF = "units.html">units</A> command for details.
	</P>
	<P>For 2d simulations specify z as 0.0, or a value within the <I>zlo zhi</I>
	setting in the data file header.
	</P>
	<P>The atom-ID is used to identify the atom throughout the simulation and
	in dump files. Normally, it is a unique value from 1 to Natoms for
	each atom. Unique values larger than Natoms can be used, but they
	will cause extra memory to be allocated on each processor, if an atom
	map array is used, but not if an atom map hash is used; see the
	<A HREF = "atom_modify.html">atom_modify</A> command for details. If an atom map is
	not used (e.g. an atomic system with no bonds), and you don't care if
	unique atom IDs appear in dump files, then the atom-IDs can all be set
	to 0.
	</P>
	<P>The molecule ID is a 2nd identifier attached to an atom. Normally, it
	is a number from 1 to N, identifying which molecule the atom belongs
	to. It can be 0 if it is an unbonded atom or if you don't care to
	keep track of molecule assignments.
	</P>
	<P>The diameter specifies the size of a finite-size spherical particle.
	It can be set to 0.0, which means that atom is a point particle.
	</P>
	<P>The ellipsoidflag, lineflag, triangleflag, and bodyflag determine
	whether the particle is a finite-size ellipsoid or line or triangle or
	body of finite size, or whether the particle is a point particle.
	Additional attributes must be defined for each ellipsoid, line,
	triangle, or body in the corresponding <I>Ellipsoids</I>, <I>Lines</I>,
	<I>Triangles</I>, or <I>Bodies</I> section.
	</P>
	<P>The <I>template-index</I> and <I>template-atom</I> are only defined used by
	<A HREF = "atom_style.html">atom_style template</A>. In this case the
	<A HREF = "molecule.html">molecule</A> command is used to define a molecule template
	which contains one or more molecules. If an atom belongs to one of
	those molecules, its <I>template-index</I> and <I>template-atom</I> are both set
	to positive integers; if not the values are both 0. The
	<I>template-index</I> is which molecule (1 to Nmols) the atom belongs to.
	The <I>template-atom</I> is which atom (1 to Natoms) within the molecule
	the atom is.
	</P>
	<P>Some pair styles and fixes and computes that operate on finite-size
	particles allow for a mixture of finite-size and point particles. See
	the doc pages of individual commands for details.
	</P>
	<P>For finite-size particles, the density is used in conjunction with the
	particle volume to set the mass of each particle as mass = density *
	volume. In this context, volume can be a 3d quantity (for spheres or
	ellipsoids), a 2d quantity (for triangles), or a 1d quantity (for line
	segments). If the volume is 0.0, meaning a point particle, then the
	density value is used as the mass. One exception is for the body atom
	style, in which case the mass of each particle (body or point
	particle) is specified explicitly. This is because the volume of the
	body is unknown.
	</P>
	<P>For atom_style hybrid, following the 5 initial values (ID,type,x,y,z),
	specific values for each sub-style must be listed. The order of the
	sub-styles is the same as they were listed in the
	<A HREF = "atom_style.html">atom_style</A> command. The sub-style specific values
	are those that are not the 5 standard ones (ID,type,x,y,z). For
	example, for the "charge" sub-style, a "q" value would appear. For
	the "full" sub-style, a "molecule-ID" and "q" would appear. These are
	listed in the same order they appear as listed above. Thus if
	</P>
	<PRE>atom_style hybrid charge sphere
	</PRE>
	<P>were used in the input script, each atom line would have these fields:
	</P>
	<PRE>atom-ID atom-type x y z q diameter density
	</PRE>
	<P>Note that if a non-standard value is defined by multiple sub-styles,
	it must appear mutliple times in the atom line. E.g. the atom line
	for atom_style hybrid dipole full would list "q" twice:
	</P>
	<PRE>atom-ID atom-type x y z q mux muy myz molecule-ID q
	</PRE>
	<P>Atom lines specify the (x,y,z) coordinates of atoms. These can be
	inside or outside the simulation box. When the data file is read,
	LAMMPS wraps coordinates outside the box back into the box for
	dimensions that are periodic. As discussed above, if an atom is
	outside the box in a non-periodic dimension, it will be lost.
	</P>
	<P>LAMMPS always stores atom coordinates as values which are inside the
	simulation box. It also stores 3 flags which indicate which image of
	the simulation box (in each dimension) the atom would be in if its
	coordinates were unwrapped across periodic boundaries. An image flag
	of 0 means the atom is still inside the box when unwrapped. A value
	of 2 means add 2 box lengths to get the unwrapped coordinate. A value
	of -1 means subtract 1 box length to get the unwrapped coordinate.
	LAMMPS updates these flags as atoms cross periodic boundaries during
	the simulation. The <A HREF = "dump.html">dump</A> command can output atom atom
	coordinates in wrapped or unwrapped form, as well as the 3 image
	flags.
	</P>
	<P>In the data file, atom lines (all lines or none of them) can
	optionally list 3 trailing integer values (nx,ny,nz), which are used
	to initialize the atom's image flags. If nx,ny,nz values are not
	listed in the data file, LAMMPS initializes them to 0. Note that the
	image flags are immediately updated if an atom's coordinates need to
	wrapped back into the simulation box.
	</P>
	<P>It is only important to set image flags correctly in a data file if a
	simulation model relies on unwrapped coordinates for some calculation;
	otherwise they can be left unspecified. Examples of LAMMPS commands
	that use unwrapped coordinates internally are as follows:
	</P>
	<UL><LI>Atoms in a rigid body (see <A HREF = "fix_rigid.html">fix rigid</A>, <A HREF = "fix_rigid.html">fix
	rigid/small</A>) must have consistent image flags, so that
	when the atoms are unwrapped, they are near each other, i.e. as a
	single body.

	<LI>If the <A HREF = "replicate.html">replicate</A> command is used to generate a larger
	system, image flags must be consistent for bonded atoms when the bond
	crosses a periodic boundary. I.e. the values of the image flags
	should be different by 1 (in the appropriate dimension) for the two
	atoms in such a bond.

	<LI>If you plan to <A HREF = "dump.html">dump</A> image flags and perform post-analysis
	that will unwrap atom coordinates, it may be important that a
	continued run (restarted from a data file) begins with image flags
	that are consistent with the previous run.
	</UL>
	<P>Atom velocities and other atom quantities not defined above are set to
	0.0 when the <I>Atoms</I> section is read. Velocities can be set later by
	a <I>Velocities</I> section in the data file or by a
	<A HREF = "velocity.html">velocity</A> or <A HREF = "set.html">set</A> command in the input
	script.
	</P>
	<HR>

	<P><I>Bodies</I> section:
	</P>
	<UL><LI>one or more lines per body

	<LI>first line syntax: atom-ID ninteger ndouble

	<PRE> ninteger = # of integer quantities for this particle
	ndouble = # of floating-point quantities for this particle
	</PRE>
	<LI>0 or more integer lines: one line for every 10 integer quantities

	<LI>0 or more double lines: one line for every 10 double quantities

	<LI>example:

	<PRE> 12 3 6
	2 3 2
	1.0 2.0 3.0 1.0 2.0 4.0
	</PRE>
	<LI>example:

	<PRE> 12 0 14
	1.0 2.0 3.0 1.0 2.0 4.0 1.0 2.0 3.0 1.0
	2.0 4.0 4.0 2.0
	</PRE>

	</UL>
	<P>The <I>Bodies</I> section must appear if <A HREF = "atom_style.html">atom_style body</A>
	is used and any atoms listed in the <I>Atoms</I> section have a bodyflag =
	1. The number of bodies should be specified in the header section via
	the "bodies" keyword.
	</P>
	<P>Each body can have a variable number of integer and/or floating-point
	values. The number and meaning of the values is defined by the body
	style, as described in the <A HREF = "body.html">body</A> doc page. The body style
	is given as an argument to the <A HREF = "atom_style.html">atom_style body</A>
	command.
	</P>
	<P>The ninteger and ndouble values determine how many integer and
	floating-point values are specified for this particle. Ninteger and
	ndouble can be as large as needed and can be different for every body.
	Integer values are then listed on subsequent lines, 10 values per
	line. Floating-point values follow on subsequent lines, again 10 per
	line. If the number of lines is not evenly divisible by 10, the last
	line in that group contains the remaining values, e.g. 4 values out of
	14 in the last example above, for floating-point values. If there are
	no values of a particular type, no lines appear for that type,
	e.g. there are no integer lines in the last example above.
	</P>
	<P>The <I>Bodies</I> section must appear after the <I>Atoms</I> section.
	</P>
	<HR>

	<P><I>Bond Coeffs</I> section:
	</P>
	<UL><LI>one line per bond type

	<LI>line syntax: ID coeffs

	<PRE> ID = bond type (1-N)
	coeffs = list of coeffs
	</PRE>
	<LI>example:

	<PRE> 4 250 1.49
	</PRE>

	</UL>
	<P>The number and meaning of the coefficients are specific to the defined
	bond style. See the <A HREF = "bond_style.html">bond_style</A> and
	<A HREF = "bond_coeff.html">bond_coeff</A> commands for details. Coefficients can
	also be set via the <A HREF = "bond_coeff.html">bond_coeff</A> command in the input
	script.
	</P>
	<HR>

	<P><I>BondAngle Coeffs</I> section:
	</P>
	<UL><LI>one line per angle type

	<LI>line syntax: ID coeffs

	<PRE> ID = angle type (1-N)
	coeffs = list of coeffs (see class 2 section of <A HREF = "angle_coeff.html">angle_coeff</A>)
	</PRE>

	</UL>
	<HR>

	<P><I>BondBond Coeffs</I> section:
	</P>
	<UL><LI>one line per angle type

	<LI>line syntax: ID coeffs

	<PRE> ID = angle type (1-N)
	coeffs = list of coeffs (see class 2 section of <A HREF = "angle_coeff.html">angle_coeff</A>)
	</PRE>

	</UL>
	<HR>

	<P><I>BondBond13 Coeffs</I> section:
	</P>
	<UL><LI>one line per dihedral type

	<LI>line syntax: ID coeffs

	<PRE> ID = dihedral type (1-N)
	coeffs = list of coeffs (see class 2 section of <A HREF = "dihedral_coeff.html">dihedral_coeff</A>)
	</PRE>

	</UL>
	<HR>

	<P><I>Bonds</I> section:
	</P>
	<UL><LI>one line per bond

	<LI>line syntax: ID type atom1 atom2

	<PRE> ID = bond number (1-Nbonds)
	type = bond type (1-Nbondtype)
	atom1,atom2 = IDs of 1st,2nd atoms in bond
	</PRE>
	<LI>example:

	<PRE> 12 3 17 29
	</PRE>

	</UL>
	<P>The <I>Bonds</I> section must appear after the <I>Atoms</I> section. All values
	in this section must be integers (1, not 1.0).
	</P>
	<HR>

	<P><I>Dihedral Coeffs</I> section:
	</P>
	<UL><LI>one line per dihedral type

	<LI>line syntax: ID coeffs

	<PRE> ID = dihedral type (1-N)
	coeffs = list of coeffs
	</PRE>
	<LI>example:

	<PRE> 3 0.6 1 0 1
	</PRE>

	</UL>
	<P>The number and meaning of the coefficients are specific to the defined
	dihedral style. See the <A HREF = "dihedral_style.html">dihedral_style</A> and
	<A HREF = "dihedral_coeff.html">dihedral_coeff</A> commands for details.
	Coefficients can also be set via the
	<A HREF = "dihedral_coeff.html">dihedral_coeff</A> command in the input script.
	</P>
	<HR>

	<P><I>Dihedrals</I> section:
	</P>
	<UL><LI>one line per dihedral

	<LI>line syntax: ID type atom1 atom2 atom3 atom4

	<PRE> ID = number of dihedral (1-Ndihedrals)
	type = dihedral type (1-Ndihedraltype)
	atom1,atom2,atom3,atom4 = IDs of 1st,2nd,3rd,4th atoms in dihedral
	</PRE>
	<LI>example:

	<PRE> 12 4 17 29 30 21
	</PRE>

	</UL>
	<P>The 4 atoms are ordered linearly within the dihedral. The <I>Dihedrals</I>
	section must appear after the <I>Atoms</I> section. All values in this
	section must be integers (1, not 1.0).
	</P>
	<HR>

	<P><I>Ellipsoids</I> section:
	</P>
	<UL><LI>one line per ellipsoid

	<LI>line syntax: atom-ID shapex shapey shapez quatw quati quatj quatk

	<PRE> atom-ID = ID of atom which is an ellipsoid
	shapex,shapey,shapez = 3 diameters of ellipsoid (distance units)
	quatw,quati,quatj,quatk = quaternion components for orientation of atom
	</PRE>
	<LI>example:

	<PRE> 12 1 2 1 1 0 0 0
	</PRE>

	</UL>
	<P>The <I>Ellipsoids</I> section must appear if <A HREF = "atom_style.html">atom_style
	ellipsoid</A> is used and any atoms are listed in the
	<I>Atoms</I> section with an ellipsoidflag = 1. The number of ellipsoids
	should be specified in the header section via the "ellipsoids"
	keyword.
	</P>
	<P>The 3 shape values specify the 3 diameters or aspect ratios of a
	finite-size ellipsoidal particle, when it is oriented along the 3
	coordinate axes. They must all be non-zero values.
	</P>
	<P>The values <I>quatw</I>, <I>quati</I>, <I>quatj</I>, and <I>quatk</I> set the orientation
	of the atom as a quaternion (4-vector). Note that the shape
	attributes specify the aspect ratios of an ellipsoidal particle, which
	is oriented by default with its x-axis along the simulation box's
	x-axis, and similarly for y and z. If this body is rotated (via the
	right-hand rule) by an angle theta around a unit vector (a,b,c), then
	the quaternion that represents its new orientation is given by
	(cos(theta/2), asin(theta/2), bsin(theta/2), c*sin(theta/2)). These
	4 components are quatw, quati, quatj, and quatk as specified above.
	LAMMPS normalizes each atom's quaternion in case (a,b,c) is not
	specified as a unit vector.
	</P>
	<P>The <I>Ellipsoids</I> section must appear after the <I>Atoms</I> section.
	</P>
	<HR>

	<P><I>EndBondTorsion Coeffs</I> section:
	</P>
	<UL><LI>one line per dihedral type

	<LI>line syntax: ID coeffs

	<PRE> ID = dihedral type (1-N)
	coeffs = list of coeffs (see class 2 section of <A HREF = "dihedral_coeff.html">dihedral_coeff</A>)
	</PRE>

	</UL>
	<HR>

	<P><I>Improper Coeffs</I> section:
	</P>
	<UL><LI>one line per improper type

	<LI>line syntax: ID coeffs

	<PRE> ID = improper type (1-N)
	coeffs = list of coeffs
	</PRE>
	<LI>example:

	<PRE> 2 20 0.0548311
	</PRE>

	</UL>
	<P>The number and meaning of the coefficients are specific to the defined
	improper style. See the <A HREF = "improper_style.html">improper_style</A> and
	<A HREF = "improper_coeff.html">improper_coeff</A> commands for details.
	Coefficients can also be set via the
	<A HREF = "improper_coeff.html">improper_coeff</A> command in the input script.
	</P>
	<HR>

	<P><I>Impropers</I> section:
	</P>
	<UL><LI>one line per improper

	<LI>line syntax: ID type atom1 atom2 atom3 atom4

	<PRE> ID = number of improper (1-Nimpropers)
	type = improper type (1-Nimpropertype)
	atom1,atom2,atom3,atom4 = IDs of 1st,2nd,3rd,4th atoms in improper
	</PRE>
	<LI>example:

	<PRE> 12 3 17 29 13 100
	</PRE>

	</UL>
	<P>The ordering of the 4 atoms determines the definition of the improper
	angle used in the formula for each <A HREF = "improper_style.html">improper
	style</A>. See the doc pages for individual styles
	for details.
	</P>
	<P>The <I>Impropers</I> section must appear after the <I>Atoms</I> section. All
	values in this section must be integers (1, not 1.0).
	</P>
	<HR>

	<P><I>Lines</I> section:
	</P>
	<UL><LI>one line per line segment

	<LI>line syntax: atom-ID x1 y1 x2 y2

	<PRE> atom-ID = ID of atom which is a line segment
	x1,y1 = 1st end point
	x2,y2 = 2nd end point
	</PRE>
	<LI>example:

	<PRE> 12 1.0 0.0 2.0 0.0
	</PRE>

	</UL>
	<P>The <I>Lines</I> section must appear if <A HREF = "atom_style.html">atom_style line</A>
	is used and any atoms are listed in the <I>Atoms</I> section with a
	lineflag = 1. The number of lines should be specified in the header
	section via the "lines" keyword.
	</P>
	<P>The 2 end points are the end points of the line segment. The ordering
	of the 2 points should be such that using a right-hand rule to cross
	the line segment with a unit vector in the +z direction, gives an
	"outward" normal vector perpendicular to the line segment.
	I.e. normal = (c2-c1) x (0,0,1). This orientation may be important
	for defining some interactions.
	</P>
	<P>The <I>Lines</I> section must appear after the <I>Atoms</I> section.
	</P>
	<HR>

	<P><I>Masses</I> section:
	</P>
	<UL><LI>one line per atom type

	<LI>line syntax: ID mass

	<PRE> ID = atom type (1-N)
	mass = mass value
	</PRE>
	<LI>example:

	<PRE> 3 1.01
	</PRE>

	</UL>
	<P>This defines the mass of each atom type. This can also be set via the
	<A HREF = "mass.html">mass</A> command in the input script. This section cannot be
	used for atom styles that define a mass for individual atoms -
	e.g. <A HREF = "atom_style.html">atom_style sphere</A>.
	</P>
	<HR>

	<P><I>MiddleBondTorsion Coeffs</I> section:
	</P>
	<UL><LI>one line per dihedral type

	<LI>line syntax: ID coeffs

	<PRE> ID = dihedral type (1-N)
	coeffs = list of coeffs (see class 2 section of <A HREF = "dihedral_coeff.html">dihedral_coeff</A>)
	</PRE>

	</UL>
	<HR>

	<P><I>Pair Coeffs</I> section:
	</P>
	<UL><LI>one line per atom type

	<LI>line syntax: ID coeffs

	<PRE> ID = atom type (1-N)
	coeffs = list of coeffs
	</PRE>
	<LI>example:

	<PRE> 3 0.022 2.35197 0.022 2.35197
	</PRE>

	</UL>
	<P>The number and meaning of the coefficients are specific to the defined
	pair style. See the <A HREF = "pair_style.html">pair_style</A> and
	<A HREF = "pair_coeff.html">pair_coeff</A> commands for details. Since pair
	coefficients for types I != J are not specified, these will be
	generated automatically by the pair style's mixing rule. See the
	individual pair_style doc pages and the <A HREF = "pair_modify.html">pair_modify
	mix</A> command for details. Pair coefficients can also
	be set via the <A HREF = "pair_coeff.html">pair_coeff</A> command in the input
	script.
	</P>
	<HR>

	<P><I>PairIJ Coeffs</I> section:
	</P>
	<UL><LI>one line per pair of atom types for all I,J with I <= J

	<LI>line syntax: ID1 ID2 coeffs

	<PRE> ID1 = atom type I = 1-N
	ID2 = atom type J = I-N, with I <= J
	coeffs = list of coeffs
	</PRE>
	<LI>examples:

	<PRE> 3 3 0.022 2.35197 0.022 2.35197
	3 5 0.022 2.35197 0.022 2.35197
	</PRE>

	</UL>
	<P>This section must have N*(N+1)/2 lines where N = # of atom types. The
	number and meaning of the coefficients are specific to the defined
	pair style. See the <A HREF = "pair_style.html">pair_style</A> and
	<A HREF = "pair_coeff.html">pair_coeff</A> commands for details. Since pair
	coefficients for types I != J are all specified, these values will
	turn off the default mixing rule defined by the pair style. See the
	individual pair_style doc pages and the <A HREF = "pair_modify.html">pair_modify
	mix</A> command for details. Pair coefficients can also
	be set via the <A HREF = "pair_coeff.html">pair_coeff</A> command in the input
	script.
	</P>
	<HR>

	<P><I>Triangles</I> section:
	</P>
	<UL><LI>one line per triangle

	<LI>line syntax: atom-ID x1 y1 x2 y2

	<PRE> atom-ID = ID of atom which is a line segment
	x1,y1,z1 = 1st corner point
	x2,y2,z2 = 2nd corner point
	x3,y3,z3 = 3rd corner point
	</PRE>
	<LI>example:

	<PRE> 12 0.0 0.0 0.0 2.0 0.0 1.0 0.0 2.0 1.0
	</PRE>

	</UL>
	<P>The <I>Triangles</I> section must appear if <A HREF = "atom_style.html">atom_style
	tri</A> is used and any atoms are listed in the <I>Atoms</I>
	section with a triangleflag = 1. The number of lines should be
	specified in the header section via the "triangles" keyword.
	</P>
	<P>The 3 corner points are the corner points of the triangle. The
	ordering of the 3 points should be such that using a right-hand rule
	to go from point1 to point2 to point3 gives an "outward" normal vector
	to the face of the triangle. I.e. normal = (c2-c1) x (c3-c1). This
	orientation may be important for defining some interactions.
	</P>
	<P>The <I>Triangles</I> section must appear after the <I>Atoms</I> section.
	</P>
	<HR>

	<P><I>Velocities</I> section:
	</P>
	<UL><LI>one line per atom
	<LI>line syntax: depends on atom style
	</UL>
	<DIV ALIGN=center><TABLE BORDER=1 >
	<TR><TD >all styles except those listed</TD><TD > atom-ID vx vy vz</TD></TR>
	<TR><TD >electron</TD><TD > atom-ID vx vy vz ervel</TD></TR>
	<TR><TD >ellipsoid</TD><TD > atom-ID vx vy vz lx ly lz</TD></TR>
	<TR><TD >sphere</TD><TD > atom-ID vx vy vz wx wy wz</TD></TR>
	<TR><TD >hybrid</TD><TD > atom-ID vx vy vz sub-style1 sub-style2 ...
	</TD></TR></TABLE></DIV>

	<P>where the keywords have these meanings:
	</P>
	<P>vx,vy,vz = translational velocity of atom
	lx,ly,lz = angular momentum of aspherical atom
	wx,wy,wz = angular velocity of spherical atom
	ervel = electron radial velocity (0 for fixed-core):ul
	</P>
	<P>The velocity lines can appear in any order. This section can only be
	used after an <I>Atoms</I> section. This is because the <I>Atoms</I> section
	must have assigned a unique atom ID to each atom so that velocities
	can be assigned to them.
	</P>
	<P>Vx, vy, vz, and ervel are in <A HREF = "units.html">units</A> of velocity. Lx, ly,
	lz are in units of angular momentum (distance-velocity-mass). Wx, Wy,
	Wz are in units of angular velocity (radians/time).
	</P>
	<P>For atom_style hybrid, following the 4 initial values (ID,vx,vy,vz),
	specific values for each sub-style must be listed. The order of the
	sub-styles is the same as they were listed in the
	<A HREF = "atom_style.html">atom_style</A> command. The sub-style specific values
	are those that are not the 5 standard ones (ID,vx,vy,vz). For
	example, for the "sphere" sub-style, "wx", "wy", "wz" values would
	appear. These are listed in the same order they appear as listed
	above. Thus if
	</P>
	<PRE>atom_style hybrid electron sphere
	</PRE>
	<P>were used in the input script, each velocity line would have these
	fields:
	</P>
	<PRE>atom-ID vx vy vz ervel wx wy wz
	</PRE>
	<P>Translational velocities can also be set by the
	<A HREF = "velocity.html">velocity</A> command in the input script.
	</P>
	<HR>

	<P><B>Restrictions:</B>
	</P>
	<P>To read gzipped data files, you must compile LAMMPS with the
	-DLAMMPS_GZIP option - see the <A HREF = "Section_start.html#start_2">Making
	LAMMPS</A> section of the documentation.
	</P>
	<P><B>Related commands:</B>
	</P>
	<P><A HREF = "read_dump.html">read_dump</A>, <A HREF = "read_restart.html">read_restart</A>,
	<A HREF = "create_atoms.html">create_atoms</A>, <A HREF = "write_data.html">write_data</A>
	</P>
	<P><B>Default:</B>
	</P>
	<P>The default for all the <I>extra</I> keywords is 0.
	</P>
	</HTML>

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