fix smd/adjust_dt command


fix ID group-ID smd/adjust_dt arg
  • ID, group-ID are documented in fix command

  • smd/adjust_dt = style name of this fix command

  • arg = s_fact

    s_fact = safety factor


fix 1 all smd/adjust_dt 0.1


The fix calculates a new stable time increment for use with the SMD time integrators.

The stable time increment is based on multiple conditions. For the SPH pair styles, a CFL criterion (Courant, Friedrichs & Lewy, 1928) is evaluated, which determines the speed of sound cannot propagate further than a typical spacing between particles within a single time step to ensure no information is lost. For the contact pair styles, a linear analysis of the pair potential determines a stable maximum time step.

This fix inquires the minimum stable time increment across all particles contained in the group for which this fix is defined. An additional safety factor s_fact is applied to the time increment.

See this PDF guide to use Smooth Mach Dynamics in LAMMPS.

Restart, fix_modify, output, run start/stop, minimize info

Currently, no part of MACHDYN supports restarting nor minimization.


This fix is part of the MACHDYN package. It is only enabled if LAMMPS was built with that package. See the Build package page for more info.