Apparent Bug in Fix GCMC

There seems to be a difference in how fix gcmc operates when hybrid vs.
non-hybrid potentials are used. In particular, the use of pair_style
hybrid causes a segmentation fault at the end of a run, and the number
of insertions and (especially) deletions doesn't match between otherwise
identical runs.

The following minimum working example seems to reproduce the problem;
uncomment the four lines in the input file to "fix" the problem:

** FILE mymol.txt **

3 atoms

Coords

1 0 0 -0.549
2 0 0 0.549
3 0 0 0

Types

1 1
2 1
3 2
** END FILE **

** FILE in.test **
units metal
atom_style bond
region myRegion block 0 10 0 10 0 10
create_box 2 myRegion
mass * 1
molecule nitrogens mymol.txt
pair_style hybrid lj/cut 12
pair_coeff 1 1 lj/cut 0.003140 3.32
pair_coeff 1 2 lj/cut 0 3.3
pair_coeff 2 2 lj/cut 0 3.3

#pair_style lj/cut 12
#pair_coeff 1 1 0.003140 3.32
#pair_coeff 1 2 0 3.3
#pair_coeff 2 2 0 3.3

fix 1 all gcmc 5000 40 500 0 1234 770 123 1 pressure 200 mol nitrogens
thermo_style custom step atoms press temp f_1[4] f_1[6] f_1[1] f_1[2]
run 100000

FYI, i've filed this as issue #81 on the LAMMPS project issue tracker
on github: https://github.com/lammps/lammps/issues/81

thanks for providing suitable test input. much appreciated.

axel.

after looking through the example input, i have to call this an invalid issue.
i cannot reproduce the segfault with the current development version
of LAMMPS, and the different behavior between hybrid and non-hybrid
for this input is actually documented behavior. using pair style
hybrid triggers the automatic application of the "full_energy" option.
if this is enabled, commenting out the non-hybrid pair style
definition results in an indentical trajectory. please see the
following excerpt from the documentation of fix gcmc.

Aha! It must have been in one of the patches between 16 May 2016
(latest "stable" version) and this morning. Thanks!