fix <fixID> <group> atc <type> <parameter_file>
 fix AtC internal atc thermal Ar_thermal.dat  
  fix AtC internal atc two_temperature Ar_ttm.mat  
  fix AtC internal atc hardy  
  fix AtC internal atc field  
 
This fix is the beginning to creating a coupled FE/MD simulation and/or an on-the-fly estimation of continuum fields. The coupled versions of this fix do Verlet integration and the /post-processing does not. After instantiating this fix, several other fix_modify commands will be needed to set up the problem, e.g. define the finite element mesh and prescribe initial and boundary conditions.
The following coupling example is typical, but non-exhaustive:
 # ... commands to create and initialize the MD system 
 # initial fix to designate coupling type and group to apply it to 
 # tag group physics material_file 
 fix AtC internal atc thermal Ar_thermal.mat
 
 # create a uniform 12 x 2 x 2 mesh that covers region contain the group 
 # nx ny nz region periodicity 
 fix_modify AtC mesh create 12 2 2 mdRegion f p p
 
 # specify the control method for the type of coupling 
 # physics control_type 
 fix_modify AtC thermal control flux 
 
 # specify the initial values for the empirical field "temperature" 
 # field node_group value 
 fix_modify AtC initial temperature all 30.
 
 # create an output stream for nodal fields 
 # filename output_frequency 
 fix_modify AtC output atc_fe_output 100
 
 run 1000 
 
likewise for this post-processing example: 
 # ... commands to create and initialize the MD system 
 # initial fix to designate post-processing and the group to apply it to 
 # no material file is allowed nor required 
 fix AtC internal atc hardy 
 
 # for hardy fix, specific kernel function (function type and range) to # be used as a localization function 
 fix AtC kernel quartic_sphere 10.0 
 
 # create a uniform 1 x 1 x 1 mesh that covers region contain the group 
 # with periodicity this effectively creats a system average 
 fix_modify AtC mesh create 1 1 1 box p p p 
 # change from default lagrangian map to eulerian 
 # refreshed every 100 steps 
 fix_modify AtC atom_element_map eulerian 100 
 
 # start with no field defined 
 # add mass density, potential energy density, stress and temperature 
 fix_modify AtC fields add density energy stress temperature 
 # create an output stream for nodal fields 
 # filename output_frequency 
 fix_modify AtC output nvtFE 100 text 
 run 1000 
 
the mesh's linear interpolation functions can be used as the localization function 
 by using the field option: 
 fix AtC internal atc field 
 
 fix_modify AtC mesh create 1 1 1 box p p p 
 ... 
 
Note coupling and post-processing can be combined in the same simulations using separate fixes. 
 For detailed exposition of the theory and algorithms please see:
Please refer to the standard finite element (FE) texts, e.g. T.J.R Hughes The finite element method , Dover 2003, for the basics of FE simulation.
Thermal and two_temperature (coupling) types use a Verlet time-integration algorithm. The hardy type does not contain its own time-integrator and must be used with a separate fix that does contain one, e.g. nve, nvt, etc.
Currently,
fix_modify commands for setup: 
fix_modify commands for boundary and initial conditions:
fix_modify commands for control and filtering: 
fix_modify commands for output: 
fix_modify commands for post-processing: 
miscellaneous fix_modify commands: 
Note: a set of example input files with the attendant material files are included with this package
none
 1.6.1
 1.6.1