forked from lijiext/lammps
80 lines
1.8 KiB
Plaintext
80 lines
1.8 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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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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angle_coeff * 75.0 :pre
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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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See "(Sun)"_#Sun for a description of the COMPASS class2 force field.
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For this style, only coefficients for the Ea formula can be specified
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in the input script. These are the 4 coefficients:
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theta0 (degrees)
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K2 (energy/radian^2)
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K3 (energy/radian^2)
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K4 (energy/radian^2) :ul
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Theta0 is specified in degrees, but LAMMPS converts it to radians
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internally; hence the units of K are in energy/radian^2.
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Coefficients for the Ebb and Eba formulas must be specified in the
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data file.
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For the Ebb formula, the coefficients are listed under a "BondBond
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Coeffs" heading and each line lists 3 coefficients:
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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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For the Eba formula, the coefficients are listed under a "BondAngle
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Coeffs" heading and each line lists 4 coefficients:
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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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This angle style is part of the "class2" package. It is only enabled
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if LAMMPS was built with that package. See the "Making
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LAMMPS"_Section_start.html#2_2 section for more info.
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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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: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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