forked from lijiext/lammps
117 lines
2.8 KiB
Plaintext
117 lines
2.8 KiB
Plaintext
"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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dihedral_style class2 command :h3
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[Syntax:]
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dihedral_style class2 :pre
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[Examples:]
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dihedral_style class2
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dihedral_coeff 1 100 75 100 70 80 60 :pre
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[Description:]
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The {class2} dihedral style uses the potential
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:c,image(Eqs/dihedral_class2.jpg)
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where Ed is the dihedral term, Embt is a middle-bond-torsion term,
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Eebt is an end-bond-torsion term, Eat is an angle-torsion term, Eaat
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is an angle-angle-torsion term, and Ebb13 is a bond-bond-13 term.
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Theta1 and theta2 are equilibrium angles and r1 r2 r3 are equilibrium
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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 Ed formula can be specified
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in the input script. These are the 6 coefficients:
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K1 (energy)
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phi1 (degrees)
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K2 (energy)
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phi2 (degrees)
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K3 (energy)
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phi3 (degrees) :ul
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Coefficients for all the other formulas must be specified in the data
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file.
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For the Embt formula, the coefficients are listed under a
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"MiddleBondTorsion Coeffs" heading and each line lists 4 coefficients:
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A1 (energy/distance)
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A2 (energy/distance)
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A3 (energy/distance)
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r2 (distance) :ul
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For the Eebt formula, the coefficients are listed under a
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"EndBondTorsion Coeffs" heading and each line lists 8 coefficients:
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B1 (energy/distance)
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B2 (energy/distance)
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B3 (energy/distance)
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C1 (energy/distance)
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C2 (energy/distance)
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C3 (energy/distance)
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r1 (distance)
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r3 (distance) :ul
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For the Eat formula, the coefficients are listed under a "AngleTorsion
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Coeffs" heading and each line lists 8 coefficients:
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D1 (energy/radian)
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D2 (energy/radian)
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D3 (energy/radian)
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E1 (energy/radian)
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E2 (energy/radian)
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E3 (energy/radian)
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theta1 (degrees)
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theta2 (degrees) :ul
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Theta1 and theta2 are specified in degrees, but LAMMPS converts them
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to radians internally; hence the units of D and E are in
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energy/radian.
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For the Eaat formula, the coefficients are listed under a
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"AngleAngleTorsion Coeffs" heading and each line lists 3 coefficients:
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M (energy/radian^2)
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theta1 (degrees)
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theta2 (degrees) :ul
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Theta1 and theta2 are specified in degrees, but LAMMPS converts them
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to radians internally; hence the units of M are in energy/radian^2.
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For the Ebb13 formula, the coefficients are listed under a "BondBond13
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Coeffs" heading and each line lists 3 coefficients:
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N (energy/distance^2)
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r1 (distance)
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r3 (distance) :ul
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[Restrictions:]
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This dihedral style is part of the "class2" package. It is only
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enabled 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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"dihedral_coeff"_dihedral_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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