Syntax:
fix ID group-ID dt/reset N Tmin Tmax Xmax keyword values ...
units value = lattice or box lattice = Xmax is defined in lattice units box = Xmax is defined in simulation box units
Examples:
fix 5 all dt/reset 10 1.0e-5 0.01 0.1 fix 5 all dt/reset 10 0.01 2.0 0.2 units box
Description:
Reset the timestep size every N steps during a run, based on current atom velocities and forces. This can be useful when starting from a configuration with overlapping atoms, where forces will be large. Or it can be useful when running an impact simulation where one or more high-energy atoms collide with a solid, causing a damage cascade.
This fix overrides the timestep size setting made by the timestep command. The new timestep size dt is computed in the following way.
Vmax is the maximum velocity; Amax is the maximum acceleration = force/mass. Note that Tmin or Tmax can be specified as INF, in which case one or both of the last 2 checks will not be performed.
When the run style is respa, this fix resets the outer loop (largest) timestep, which is the same timestep that the timestep command sets.
Restart, fix_modify, output, run start/stop, minimize info:
No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix.
The current timestep size is stored as a scalar quantity by this fix. The cummulative simulation time (in time units) is stored as the first element of a vector. Both these quantities can be accessed by various output commands. The scalar and vector values calculated by this fix are "intensive", meaning they are independent of the number of atoms in the simulation.
No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.
Restrictions:
The cummulative time is zeroed when the fix is created and continuously accrues thereafter. Using the reset_timestep command while this fix is defined will mess up the time accumulation.
Related commands:
Default:
The option defaults is units = lattice.