Hello everyone

I reckon that there is an ambiguity with the description of the “compute group/group” command in the manual. it says:

“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.”

What is it exactly? The total energy or the force?

regards

Toon

From the “Output info” section of compute group/group: “This compute calculates a global scalar (the energy) and a global vector of length 3 (force), which can be accessed by indices 1-3. These values can be used by any command that uses global scalar or vector values from a compute as input. See the Howto output doc page for an overview of LAMMPS output options.”

Will

Hi Toon,

here is the output information about this command.

**Output info:**

This compute calculates a global scalar (the energy) and a global vector of length 3 (force), which can be accessed by indices 1-3. These values can be used by any command that uses global scalar or vector values from a compute as input. See the Howto output doc page for an overview of LAMMPS output options.

Both the scalar and vector values calculated by this compute are “extensive”. The scalar value will be in energy units. The vector values will be in force units.

For example, compute 1 lower group/group upper

To access the interaction energy , you can use c_1

To access the interaction force in x y z direction : c_1[1] c_1[2] c_1[3]

Hello Dezhao Huang

Thank you for your kind reply. It was quite a lot of helpful.

regards

Toon