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### gran rolling_friction cdt

Syntax:

    rolling_friction cdt

LIGGGHTS vs. LAMMPS Info:

This part of pair gran and fix wall/gran is not availabe in LAMMPS.

Description:

This model can be used as part of pair gran and fix wall/gran

The constant directional torque (CDT) model adds an additional torque contribution, equal to

torque_rf = rmu*k_n*delta_n*w_r_shear/mag(w_r_shear)*(R*).

w_r_shear is the projection of w_r into the shear plane, where w_r = w1-w2

If the rolling friction model is activated, the coefficient of rolling friction (rmu) must be defined as

    fix id all property/global coefficientRollingFriction peratomtypepair n_atomtypes value_11 value_12 .. value_21 value_22 .. .
        (value_ij=value for the coefficient of rolling friction between atom type i and j; n_atomtypes is the number of atom types you want to use in your simulation)

IMPORTANT NOTE: You have to use atom styles beginning from 1, e.g. 1,2,3,...

(Ai) Jun Ai, Jian-Fei Chen, J. Michael Rotter, Jin Y. Ooi, Powder Technology, 206 (3), p 269-282 (2011).