Syntax:
bond_style gran/disk
bond_style gran/disk/waves
Examples:
bond_style gran/disk bond_style gran/disk/waves bond_coeff 1 0.8 1.0 0.0 0.9 8e9 2.5 1 1e6 1e5 1e6
Description:
These bond styles are part of the USER-SEAICE package; they are only enabled if LIGGGHTS was built with that package.
The gran/disk style, in combination with atom_style hybrid disk bond/gran/disk can be used in a general context to model bonded, disk-shaped granular particles in 2D. The gran/disk/waves style is specifically dedicated to simulation of wave-induced bending and twisting moments acting on ice floes on the sea surface. It requires atom_style hybrid disk disk/waves bond/gran/disk.
The following coefficients must be defined for each bond type via the bond_coeff command as in the example above. The syntax of the bond_coeff command in this case is:
bond_coeff N lambdaR thb delthb lambdab Eb lambdans breakmode sigmamaxc sigmamaxt taumax
where:
At present, only breakmode=1 is allowed, which means stress-induced bond breaking that occurs if at least one of the three breaking criteria is fullfilled. The bond-thickness distribution is uniform, with mean equal thb and width equal delthb (may be zero).
A constant damping coefficient of 0.995 is used in the formulae for the forces and torques acting on the bonds.
If granular bonds are used, the following settings are required and/or strongly recommended:
newton off off communicate single cutoff value vel yes special_bonds lj/coul 0 1 1 extra Ne
Due to the first setting, forces due to pairwise and bonded interactions between atoms belonging to different processors are calculated by each processor separately, instead of being communicated between processors; see newton command for details. As a result of the second command, velocities, necessary to calculate pairwise interactions, are stored by ghosts atoms; see communicate command for details. For simulations with bonds, the value of the ghost cutoff distance value should be larger than the longest bond in the system, so that the bond information is correctly passed between processors. The third command is an artefact from other bond types, in which interactions may be computed not only between atoms directly connected with a bond, but also between atoms connected via other atoms; in the case of granular bonds, changing the weights for indirect interactions from 1 to 0 doesn't influence the results, but unnecessarily increases the amount of memory; the same effect occurs if the special_bonds command is not used at all; the value Ne specifies the number of extra space saved for bonds that may be created during the simulation with the fix bond/create/gran/disk command; it may be zero if bonds are read from an input file at the beginning of the simulation and the information about the maximum number of neighbors is read from that file.
Related commands:
atom_style hybrid disk bond/gran/disk, bond_coeff, fix bond/create/gran/disk, read_data
Default: none
(Herman) Agnieszka Herman, Geosci. Model Devel., submitted (2015).