bond_style mm3 command


bond_style mm3


bond_style mm3
bond_coeff 1 100.0 107.0


The mm3 bond style uses the potential that is anharmonic in the bond as defined in (Allinger)

\[E = K (r - r_0)^2 \left[ 1 - 2.55(r-r_0) + \frac{7}{12} 2.55^2(r-r_0)^2 \right]\]

where \(r_0\) is the equilibrium value of the bond, and \(K\) is a prefactor. The anharmonic prefactors have units \(\AA^{-n}\): \(-2.55 \AA^{-1}\) and \(\frac{7}{12} 2.55^2 \AA^{-2}\). The code takes care of the necessary unit conversion for these factors internally. Note that the MM3 papers contain an error in Eq (1): \(\frac{7}{12} 2.55\) should be replaced with \(\frac{7}{12} 2.55^2\)

The following coefficients must be defined for each bond type via the bond_coeff command as in the example above, or in the data file or restart files read by the read_data or read_restart commands:

  • \(K\) (energy/distance^2)

  • \(r_0\) (distance)


This bond style can only be used if LAMMPS was built with the YAFF package. See the Build package doc page for more info.



(Allinger) Allinger, Yuh, Lii, JACS, 111(23), 8551-8566 (1989),