forked from lijiext/lammps
68 lines
2.3 KiB
Plaintext
68 lines
2.3 KiB
Plaintext
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"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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lattice command :h3
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[Syntax:]
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lattice style value :pre
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style = {none} or {sc} or {bcc} or {fcc} or {sq} or {sq2} or {hex} or {diamond} :ulb,l
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{none} value = none
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for all other styles:
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value = reduced density (for LJ units)
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value = cubic lattice constant in Angstroms (for real or metal units) :pre
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:ule
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[Examples:]
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lattice fcc 3.52
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lattice hex 0.85
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lattice none :pre
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[Description:]
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Define a lattice type and lattice constant. This is required before
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using a commands that (optionally) use the lattice, such as
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"create_atoms"_create_atoms.html or "region"_region.html. The lattice
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type must be consistent with the dimension of the simulation - see the
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"dimension"_dimension.html command. Styles {sc} or {bcc} or {fcc} or
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{diamond} are for 3d problems. Styles {sq} or {sq2} or {hex} are for
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2d problems. Lattices of style {fcc}, {bcc}, {hex}, or {diamond} are
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described in any solid-state physics text. A {sc} lattice is simple
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cubic, with atoms at the corners of a cube. A {sq} lattice is square
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with atoms at the corners of a square. A {sq2} lattice is a {sq}
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lattice with an additional atom at the center of the square.
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For unit style {real} or {metal}, the specified value is the cubic
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lattice constant in Angstroms. For unit style {lj}, the value is the
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reduced density (rho*) which LAMMPS converts into a cubic lattice
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constant. For 3d problems, the relationship "rho* = rho sigma^3" is
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used for the conversion, where rho = N/V with V = the volume of the
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cubic cell and N = 4 for {fcc}, 2 for {bcc}, 1 for {sc}, and 8 for
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{diamond} lattices. For 2d problems, the relationship "rho* = rho
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sigma^2" is used for the conversion, where N = 2 for {sq2} or {hex}
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and 1 for {sq}. In the hex case, the unit cell is actually
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rectangular; it is extended by a factor of sqrt(3) in the y-dimension.
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The command "lattice none" can be used to turn off the lattice
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setting. Any command that attempts to use a lattice constant will
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then generate an error.
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[Restrictions:] none
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[Related commands:]
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"dimension"_dimension.html, "orient"_orient.html,
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"origin"_origin.html, "create_atoms"_create_atoms.html,
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"region"_region.html
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[Default:]
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lattice none :pre
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