Pair coeffs not set (error) using hybrid/overlay during rerun


I have a low priority problem that I was wondering if anyone could help me with:

The error: ERROR: All pair coeffs are not set (pair.cpp:168)

I’ve spent some time trying to troubleshoot this error but have been unable to figure out the source of the error despite browsing the source code.

I am executing a “rerun” over a series of dump files (explicitly listed in order). I am using the method of reading in the original data file (with box definitions, masses, atom coordinates, and bond topology) and then running “rerun” with the keyword “dump” and options “x y z vx vy vz”.

My goal in the rerun simulation is to generate pairwise energy data using “compute group/group” and “compute pair”. “group/group” is being used to look specifically at the individual atom-type pair interactions. To do this without getting a “single call” error, I have to remove the “dpd/tstat” pair style such that my modified pair_styles look as follows:

readjust bond style

bond_style fene
bond_coeff 1 30.0 1.5 1.0 1.0
special_bonds lj 0 1 1

Combined pair styles

pair_style hybrid/overlay dpd/tstat {T_set} {T_set} 2.5 16523 lj/gromacs 1.9149 2.5 lj/cut 1.122462048 lj/expand 5.0 colloid 10.0 # <-- original style

pair_style hybrid/overlay lj/gromacs 1.9149 2.5 lj/cut 1.122462048 lj/expand 5.0 colloid 10.0 # <–rerun style

pair_coeff * * dpd/tstat 1.0 2.5 # <-- original style

pair_coeff 1 1 lj/gromacs 1.0 1.0
pair_coeff 2 2 lj/gromacs 1.0 1.0
pair_coeff 2 4 lj/gromacs 0.8 1.0 # weaker W-B
pair_coeff 4 4 lj/cut 0.25 1.0 # purely repulsive B-B
pair_coeff 1 2 lj/cut 0.25 1.0 # purely repulsive A-W
pair_coeff 1 4 lj/cut 0.25 1.0 # purely repulsive A-B

pair_coeff 1 3 lj/expand 0.25 1.0 2.5 3.622462048 # purely repulsive shifted LJ potential
pair_coeff 2 3 lj/expand {NP_W} 1.0 2.5 # variable pair_coeff 3 4 lj/expand {NP_B} 1.0 2.5 # neutral
pair_coeff 3 3 colloid ${Ann} 1.0 6.0 6.0 10.5 # neutral

As far as I understand, I should have all pair coeffs for all i <= j pair combinations set to at least one pair style, as above. I can avoid the error by adding “pair_coeff * * none” before I define any of the other pair_coeffs just to set the flags for each pair combination, but I don’t understand why it’s necessary. It may be worth noting that this particular simulation did not have any atoms of “type 3” present.

Thanks for any help.

  • Bryan

Without dpd/tstat you need to use pair style hybrid. Axel.

Oh, yup. That makes a lot of sense. Thanks for the reply!

  • Bryan