Interaction energy between solutes : problem with compute group//group command

Dear all,
I’m trying to simulate the polymer interaction with ion in presence of water. The whole system consist of one polymer chain and and one ion surrounded by 1000 water molecules. For water I have used TIP4P/2005 water model. If I use group/group command in Lammps to calculate the interaction energy, it shows the error message of " Pair style does not support compute group/group", The same error message was indicated even if I use SPC water model.

Is there any other method by which I can calculate the interaction energy between polymer and ion. My polymer chain consist of 100 atoms. I look forward for your advice …

Thanks in Advance,

Pooja

Dear all,
     I'm trying to simulate the polymer interaction with ion in presence of
water. The whole system consist of one polymer chain and and one ion
surrounded by 1000 water molecules. For water I have used TIP4P/2005 water
model. If I use group/group command in Lammps to calculate the interaction
energy, it shows the error message of " Pair style does not support compute
group/group", The same error message was indicated even if I use SPC water
model.

Is there any other method by which I can calculate the interaction energy
between polymer and ion. My polymer chain consist of 100 atoms. I look
forward for your advice ..

the only alternative LAMMPS offers to compute subsets of interaction
energies, is the rerun command.
this will use a trajectory generated with all interactions, but you
would compute only the interactions, you are interested in during
rerun. if needed, multiple times with different subsets.

axel.

Dear Axel,

As I could understood from LAMMPS Documentation that rerun command is used to rerun the simulation with modified potential …like modified interaction range … or modified electrostatic interactions and analyse the modified trajectory. However, in the present case I don’t want to change the potential. I only want to calculate the interaction energy between polymer and ion. I am not getting how I can use rerun command to calculate interaction energy between these two groups … Pls help me in understanding it …

With Thanks and Regards,

Pooja

Dear Axel,
As I could understood from LAMMPS Documentation that rerun command is used
to rerun the simulation with modified potential ..like modified interaction
range .. or modified electrostatic interactions and analyse the modified
trajectory. However, in the present case I don't want to change the
potential. I only want to calculate the interaction energy between polymer
and ion. I am not getting how I can use rerun command to calculate
interaction energy between these two groups .. Pls help me in understanding
it ..

how? the way to go about it is, exactly what i explained already.
if you can't grasp the (really simple) concept, then there is no way
of helping you.

axel.

This is conceptually the same as changing the potential. After all, you really want a potential in which all interactions except those between the polymer and the water are 0.