compute dihedral/local command
compute ID group-ID dihedral/local value1 value2 ...
ID, group-ID are documented in compute command
dihedral/local = style name of this compute command
one or more values may be appended
value = phi
phi = tabulate dihedral angles
compute 1 all dihedral/local phi
Define a computation that calculates properties of individual dihedral interactions. The number of datums generated, aggregated across all processors, equals the number of angles in the system, modified by the group parameter as explained below.
The value phi is the dihedral angle, as defined in the diagram on the dihedral_style doc page.
The local data stored by this command is generated by looping over all the atoms owned on a processor and their dihedrals. A dihedral will only be included if all 4 atoms in the dihedral are in the specified compute group.
Note that as atoms migrate from processor to processor, there will be no consistent ordering of the entries within the local vector or array from one timestep to the next. The only consistency that is guaranteed is that the ordering on a particular timestep will be the same for local vectors or arrays generated by other compute commands. For example, dihedral output from the compute property/local command can be combined with data from this command and output by the dump local command in a consistent way.
Here is an example of how to do this:
compute 1 all property/local dtype datom1 datom2 datom3 datom4 compute 2 all dihedral/local phi dump 1 all local 1000 tmp.dump index c_1 c_1 c_1 c_1 c_1 c_2
This compute calculates a local vector or local array depending on the number of keywords. The length of the vector or number of rows in the array is the number of dihedrals. If a single keyword is specified, a local vector is produced. If two or more keywords are specified, a local array is produced where the number of columns = the number of keywords. The vector or array can be accessed by any command that uses local values from a compute as input. See this section for an overview of LAMMPS output options.
The output for phi will be in degrees.