group_num new_group_number restart_group_number fix_number cal_number
cal_number= non-negative integer (<= 40)
group_num 3 0 3 0 group_num 2 1 1 2
This command sets the numbers of new groups, restart groups, fix, and calculations. In CAC, a group is a collection of elements/nodes/atoms. There are two purposes of having groups: (i) to apply a displacement/force to certain elements/nodes/atoms, (ii) to calculate some mechanical quantities, e.g., energy, force, and stress, of certain elements/nodes/atoms.
The new groups are defined in the group command. The elements/nodes/atoms contained in the restart groups, named
group_*, are read from the
group_in_*.id files, where
* is a positive integer starting from
new_group_number + 1, yet their displacement/force information is set in the fix command.
The total number of groups, i.e.,
restart_group_number, cannot be larger than 40. Files
group_in_*.id contain information of the restart groups. On the one hand, there cannot be fewer
group_in_*.id files than
restart_group_number; on the other hand, any
group_in_*.id file with
restart_group_number will be ignored. When
boolean_restart = f,
restart_group_number becomes 0, regardless of its value set in this command.
fix_number should not be larger than
restart_group_number; neither should
cal_number should not be smaller than
group_num 0 0 0 0