2006-09-22 00:22:34 +08:00
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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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angle_style class2 command :h3
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[Syntax:]
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angle_style class2 :pre
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[Examples:]
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angle_style class2
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2010-11-18 02:25:09 +08:00
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angle_coeff * 75.0
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2010-11-19 01:28:36 +08:00
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angle_coeff 1 bb 10.5872 1.0119 1.5228
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angle_coeff * ba 3.6551 24.895 1.0119 1.5228 :pre
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2006-09-22 00:22:34 +08:00
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[Description:]
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The {class2} angle style uses the potential
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:c,image(Eqs/angle_class2.jpg)
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where Ea is the angle term, Ebb is a bond-bond term, and Eba is a
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bond-angle term. Theta0 is the equilibrium angle and r1 and r2 are
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the equilibrium bond lengths.
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2006-09-28 03:12:31 +08:00
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See "(Sun)"_#Sun for a description of the COMPASS class2 force field.
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2010-11-18 02:20:48 +08:00
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Coefficients for the Ea, Ebb, and Eba formulas must be defined for
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each angle type via the "bond_coeff"_bond_coeff.html command as in the
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example above, or in the data file or restart files read by the
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"read_data"_read_data.html or "read_restart"_read_restart.html
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commands.
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These are the 4 coefficients for the Ea formula:
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2006-09-22 00:22:34 +08:00
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theta0 (degrees)
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K2 (energy/radian^2)
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2008-02-01 02:14:21 +08:00
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K3 (energy/radian^3)
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K4 (energy/radian^4) :ul
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2006-09-22 00:22:34 +08:00
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Theta0 is specified in degrees, but LAMMPS converts it to radians
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2008-02-01 02:14:21 +08:00
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internally; hence the units of the various K are in per-radian.
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2006-09-22 00:22:34 +08:00
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2010-11-18 02:20:48 +08:00
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For the Ebb formula, each line in a "bond_coeff"_bond_coeff.html
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command in the input script lists 4 coefficients, the first of which
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is "bb" to indicate they are BondBond coefficients. In a data file,
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2010-11-18 02:25:09 +08:00
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these coefficients should be listed under a "BondBond Coeffs" heading
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and you must leave out the "bb", i.e. only list 3 coefficients after
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the angle type.
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2006-09-22 00:22:34 +08:00
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2010-11-18 02:20:48 +08:00
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bb
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2006-09-22 00:22:34 +08:00
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M (energy/distance^2)
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r1 (distance)
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r2 (distance) :ul
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2010-11-18 02:20:48 +08:00
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For the Eba formula, each line in a "bond_coeff"_bond_coeff.html
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command in the input script lists 5 coefficients, the first of which
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is "ba" to indicate they are BondAngle coefficients. In a data file,
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2010-11-18 02:25:09 +08:00
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these coefficients should be listed under a "BondAngle Coeffs" heading
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2010-11-18 02:20:48 +08:00
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and you must leave out the "ba", i.e. only list 4 coefficients after
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the angle type.
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2006-09-22 00:22:34 +08:00
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2010-11-18 02:20:48 +08:00
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ba
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2006-09-22 00:22:34 +08:00
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N1 (energy/distance^2)
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N2 (energy/distance^2)
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r1 (distance)
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r2 (distance) :ul
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The theta0 value in the Eba formula is not specified, since it is the
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same value from the Ea formula.
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[Restrictions:]
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2007-06-26 08:03:39 +08:00
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This angle style can only be used if LAMMPS was built with the
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"class2" package. See the "Making LAMMPS"_Section_start.html#2_3
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section for more info on packages.
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2006-09-22 00:22:34 +08:00
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[Related commands:]
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"angle_coeff"_angle_coeff.html
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[Default:] none
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2006-09-28 03:12:31 +08:00
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:line
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:link(Sun)
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[(Sun)] Sun, J Phys Chem B 102, 7338-7364 (1998).
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