implementing new fix and neighbor list

Hello lammps developers,

I try to implemented a new fix to use the test area simulation method
(Gloor et al., J. Chem. Phys. 123, 134703(2005)) to calculated the
interfacial free energy between two immiscible liquids, in this method the
interfacial area is slightly increased or reduced but the volume of system
not change (NVT simulations), this fix in the n step, calculated the
difference of potential energy between the reference and the perturbed
systems.
Where the perturbed systems correspond to the reference system with the
sides of box are slightly modified but the scaled positions not change.
So I realize test of the new fix, the first three calculation with the fix
run okey but in for the 4 step, something must be happening with the
construction of the neighbor list, in log file show the following message.

    2995 0.99247481 -33796.057 16000 0.20992682
    2996 0.99258516 -33797.866 16000 0.20969392
    2997 0.99276093 -33800.964 16000 0.2091864
    2998 0.99311765 -33805.651 16000 0.20817756
    2999 0.99371015 -33814.474 16000 0.20625962
    3000 0.99391154 -33825.716 16000 0.20337434
    3001 0 8.6947514e+23 16000 2.1736879e+20
    3002 0 -32722.066 16000 -0.37409011
    3003 0 -32770.927 16000 -0.39041893
    3004 0 -32818.245 16000 -0.40627815
    3005 0 -32864.216 16000 -0.42170735
    3006 0 -32908.689 16000 -0.43670196
    3007 0 -32951.803 16000 -0.45129169
ERROR: Lost atoms: original 9032 current 9030 (../thermo.cpp:394)

is possible check the my code fix_tasm.cpp, specially the function:
void FixTASM::neighbor_settings() (lines 587 - 615)
actually is prototype version and only work with a lennard-jones liquid,
but I intend to modify to use a molecular systems.
Thanks so much to help me
Samuel

fix_tasm.cpp (16.2 KB)

fix_tasm.h (2.89 KB)

in.tasm (756 Bytes)

interface.top (244 KB)

log.lammps (185 KB)

tasm.dat (337 Bytes)