[lammps-users] Problem in treating fullerene(C60) as rigid body

Dear All:
          I am trying to simulate a system consisting of fullerene
molecules
on heterogeneous silicon surface having defects using lammps. The
surface contains two types of silicon atoms, on the top of which

there are some fullerene molecules. The surface atoms are supposed
to keep
frozen during simulation and fullerene molecules are treated as
rigid body.
For the sake of simplicity, I have taken a
homogeneous silicon surface containing only one type of silicon

atoms and few fullerene molecules on the top.

units           real
atom_style      atomic
boundary p p p
read_data       [data.si](http://data.si)
pair_style      tersoff
pair_coeff * * SiC.tersoff Si C

velocity        all create 300.0 352839
timestep        1.0
group          clump1 id <> 1 3276
group           c60 id <> 3277 4236
fix 1 clump1 recenter INIT INIT INIT units box
fix 2 c60 rigid molecule

#fix 2 c60 nve
#fix 2 c60 nvt 300.0 300.0 100.0
thermo          100
dump            1 all xyz 50 dump.c60
run             2000

#data file Si and C60

4236     atoms
2        atom types

-31.7 31.7 xlo xhi

-57.2 57.2 ylo yhi
-75.0 75.0 zlo zhi

Masses

  1 28.0000
  2 12.0000

Atoms

         atom-type            x           y            z
    1        1           -31.1849995  31.1850204   3.0400000

  -----     ---             -----        ----         ---
  3276       1             ----         ----         ----
  -----     ---             ----         ----         ----
  3277       2              ---           ---          --

  ----      ---             ---          ---          ---
  4236       2              ---          --           --

then it is showing error: Must use a molecular atom style with fix
rigid
molecule,
 then I moved to  "fix 2 c60 rigid single", then I found that all the

fullerene molecules are moving as a single body and silicon surface
remain as
stationary. After that I changed atom_style to "atom_style
molecular" along
with

the data file-
group           c60 id <> 3277 4236

fix 1 clump1 recenter INIT INIT INIT units box
fix 2 c60 rigid molecule

and data file having format as given below

4236     atoms
2        atom types

-31.7 31.7 xlo xhi
-57.2 57.2 ylo yhi

-75.0 75.0 zlo zhi

Masses

  1 28.0000
  2 12.0000

Atoms

         molecule-tag    atom-type          x           y            z
    1        1               1         -31.1849995  31.1850204  

3.0400000
  -----                     ---             -----        ----       ---
   3276      1              ----            ----         ----

If you want to use fix rigid molecule, then the clumps
of atoms you want to be rigid (fullerenes) have to
have a moleclue ID in the data file. Hence you need
to use atom_style molecular or another one that
includes moleclue IDs. Atom_style molecular does
not define charges, so I don't follow your comment on q.

If you assign molecule IDs correctly, then each fullerene
will be your rigid body. I.e. different mol IDs for
the atoms of each fullerene.

Steve