"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c :link(lws,http://lammps.sandia.gov) :link(ld,Manual.html) :link(lc,Section_commands.html#comm) :line dihedral_style class2 command :h3 dihedral_style class2/omp command :h3 [Syntax:] dihedral_style class2 :pre [Examples:] dihedral_style class2 dihedral_coeff 1 100 75 100 70 80 60 dihedral_coeff * mbt 3.5945 0.1704 -0.5490 1.5228 dihedral_coeff * ebt 0.3417 0.3264 -0.9036 0.1368 0.0 -0.8080 1.0119 1.1010 dihedral_coeff 2 at 0.0 -0.1850 -0.7963 -2.0220 0.0 -0.3991 110.2453 105.1270 dihedral_coeff * aat -13.5271 110.2453 105.1270 dihedral_coeff * bb13 0.0 1.0119 1.1010 :pre [Description:] The {class2} dihedral style uses the potential :c,image(Eqs/dihedral_class2.jpg) where Ed is the dihedral term, Embt is a middle-bond-torsion term, Eebt is an end-bond-torsion term, Eat is an angle-torsion term, Eaat is an angle-angle-torsion term, and Ebb13 is a bond-bond-13 term. Theta1 and theta2 are equilibrium angles and r1 r2 r3 are equilibrium bond lengths. See "(Sun)"_#Sun for a description of the COMPASS class2 force field. Coefficients for the Ed, Embt, Eebt, Eat, Eaat, and Ebb13 formulas must be defined for each dihedral type via the "dihedral_coeff"_dihedral_coeff.html command as in the example above, or in the data file or restart files read by the "read_data"_read_data.html or "read_restart"_read_restart.html commands. These are the 6 coefficients for the Ed formula: K1 (energy) phi1 (degrees) K2 (energy) phi2 (degrees) K3 (energy) phi3 (degrees) :ul For the Embt formula, each line in a "dihedral_coeff"_dihedral_coeff.html command in the input script lists 5 coefficients, the first of which is "mbt" to indicate they are MiddleBondTorsion coefficients. In a data file, these coefficients should be listed under a "MiddleBondTorsion Coeffs" heading and you must leave out the "mbt", i.e. only list 4 coefficients after the dihedral type. mbt A1 (energy/distance) A2 (energy/distance) A3 (energy/distance) r2 (distance) :ul For the Eebt formula, each line in a "dihedral_coeff"_dihedral_coeff.html command in the input script lists 9 coefficients, the first of which is "ebt" to indicate they are EndBondTorsion coefficients. In a data file, these coefficients should be listed under a "EndBondTorsion Coeffs" heading and you must leave out the "ebt", i.e. only list 8 coefficients after the dihedral type. ebt B1 (energy/distance) B2 (energy/distance) B3 (energy/distance) C1 (energy/distance) C2 (energy/distance) C3 (energy/distance) r1 (distance) r3 (distance) :ul For the Eat formula, each line in a "dihedral_coeff"_dihedral_coeff.html command in the input script lists 9 coefficients, the first of which is "at" to indicate they are AngleTorsion coefficients. In a data file, these coefficients should be listed under a "AngleTorsion Coeffs" heading and you must leave out the "at", i.e. only list 8 coefficients after the dihedral type. at D1 (energy/radian) D2 (energy/radian) D3 (energy/radian) E1 (energy/radian) E2 (energy/radian) E3 (energy/radian) theta1 (degrees) theta2 (degrees) :ul Theta1 and theta2 are specified in degrees, but LAMMPS converts them to radians internally; hence the units of D and E are in energy/radian. For the Eaat formula, each line in a "dihedral_coeff"_dihedral_coeff.html command in the input script lists 4 coefficients, the first of which is "aat" to indicate they are AngleAngleTorsion coefficients. In a data file, these coefficients should be listed under a "AngleAngleTorsion Coeffs" heading and you must leave out the "aat", i.e. only list 3 coefficients after the dihedral type. aat M (energy/radian^2) theta1 (degrees) theta2 (degrees) :ul Theta1 and theta2 are specified in degrees, but LAMMPS converts them to radians internally; hence the units of M are in energy/radian^2. For the Ebb13 formula, each line in a "dihedral_coeff"_dihedral_coeff.html command in the input script lists 4 coefficients, the first of which is "bb13" to indicate they are BondBond13 coefficients. In a data file, these coefficients should be listed under a "BondBond13 Coeffs" heading and you must leave out the "bb13", i.e. only list 3 coefficients after the dihedral type. bb13 N (energy/distance^2) r1 (distance) r3 (distance) :ul :line Styles with a {cuda}, {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are functionally the same as the corresponding style without the suffix. They have been optimized to run faster, depending on your available hardware, as discussed in "Section_accelerate"_Section_accelerate.html of the manual. The accelerated styles take the same arguments and should produce the same results, except for round-off and precision issues. These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL, KOKKOS, USER-OMP and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the "Making LAMMPS"_Section_start.html#start_3 section for more info. You can specify the accelerated styles explicitly in your input script by including their suffix, or you can use the "-suffix command-line switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can use the "suffix"_suffix.html command in your input script. See "Section_accelerate"_Section_accelerate.html of the manual for more instructions on how to use the accelerated styles effectively. :line [Restrictions:] This dihedral style can only be used if LAMMPS was built with the CLASS2 package. See the "Making LAMMPS"_Section_start.html#start_3 section for more info on packages. [Related commands:] "dihedral_coeff"_dihedral_coeff.html [Default:] none :line :link(Sun) [(Sun)] Sun, J Phys Chem B 102, 7338-7364 (1998).