A simple source of confusion occurs when one reads the doc pages of the following
Thermo_style
compute pair
compute group/group
- For example this line in thermo_style doc pages
epair = pairwise energy (evdwl + ecoul + elong + etail)
But further reading the doc page of thermo_style, it is mentioned that evdwl includes etail. So the above statement on the top of the page is slightly misleading i.e it appears as though edvwl does not include tail corrections but it does include tail corrections. However ecoul does not inlcude elong !
So please change the above statement to
epair = pairwise energy (evdwl + ecoul+elong )
to easily verify the above equality
- When going through the doc pages of compute pair command, the short form of vanderwaals interaction “evdwl” is used. However the evdwl does not include the tail corrections. This is inconsistent with the symbol used in thermo_style doc pages. similarly “ecoul” does not include elong. But this however is consistent with the shortform ecoul used in thermo_style doc pages.
In the compute pair doc pages it would be useful to mention evdwl does not inlcude tail corrections.
- Now if one were to use compute group/group command like this
compute 2 all group/group all pair yes
It would give the total pairwise potential energy of the system. Again this does not add tail corrections elong and etail to the pair wise energies.
Please mention this in the doc pages.
If I am mistaken please correct my understanding.
Thanks
Arun
Verification:
LAMMPS 15th may 2015
compute 1 all pair lj/cut/coul/long
compute 2 all group/group all pair yes
Step E_vdwl E_tail E_coul E_long E_pair 1 2
0 -756.46009 -885.64181 30935.469 -31524.447 -1345.4383 31064.65 31064.65
1 -781.76004 -885.64164 30935.882 -31524.51 -1370.3881 31039.764 31039.764
Loop time of 0.587527 on 1 procs for 1 steps with 15680 atoms
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compute 1 all pair lj/cut/coul/long evdwl
compute 2 all group/group all pair yes
Step E_vdwl E_tail E_coul E_long E_pair 1 2
0 -756.46009 -885.64181 30935.469 -31524.447 -1345.4383 129.18173 31064.65
1 -781.76004 -885.64164 30935.882 -31524.51 -1370.3881 103.8816 31039.764
Loop time of 0.584007 on 1 procs for 1 steps with 15680 atoms