fix_modify AtC time_integration <descriptor> 
various time integration methods for the finite elements
 
gear - atomic velocity update with 2nd order Verlet, nodal temperature update with 3rd or 4th order Gear, thermostats based on controlling power 
 fractional_step - atomic velocity update with 2nd order Verlet, mixed nodal temperature update, 3/4 Gear for continuum and 2 Verlet for atomic contributions, thermostats based on controlling discrete energy changes
 
 fix_modify atc time_integration gear  
  fix_modify atc time_integration fractional_step  
 
see fix atc command
none
 1.6.1
 1.6.1