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compute group/group command

Syntax:

compute ID group-ID group/group group2-ID 

Examples:

compute 1 lower group/group upper
compute mine fluid group/group wall 

Description:

Define a computation that calculates the total energy and force interaction between two groups of atoms: the compute group and the specified group2. The two groups can be the same. The interaction energy is defined as the pairwise energy between all pairs of atoms where one atom in the pair is in the first group and the other is in the second group. Likewise, the interaction force calculated by this compute is the force on the compute group atoms due to pairwise interactions with atoms in the specified group2.

The energy and force are calculated by looping over a neighbor list of pairwise interactions. Thus it can be inefficient to compute this quantity too frequently.

Output info:

The interaction energy calculated by this compute is a scalar quantity. The interaction force is a vector of length 3. Both the scalar and vector values calculated by this compute are "extensive", meaning they scale with the number of atoms in the simulation.

Restrictions:

Only pairwise interactions, as defined by the pair_style command, are included in this calculation. Bond (angle, dihedral, etc) interactions between atoms in the two groups are not included. Long-range interactions due to a kspace_style command are also not included. Not all pair potentials can be evaluated in a pairwise mode as required by this compute. For example, 3-body potentials, such as Tersoff and Stillinger-Weber cannot be used. EAM potentials for metals only include the pair potential portion of the EAM interaction, not the embedding term.

Related commands: none

Default: none