Friction coefient calculation getting error in thermo style

i want to calculate friction between water and graphite…
#LAMMPS Input file generated by Avogadro

MD simulation for SPCE

units real
variable T equal 283.15 #86.4956
variable V equal vol
variable dt equal 1
variable p equal 5000 # correlation length
variable s equal 10 # sample interval
variable d equal $p*$s # dump interval

convert from LAMMPS real units to SI

variable kB equal 1.3806504e-23 # [J/K/** Boltzmann
variable atm2Pa equal 101325.0
variable A2m equal 1.0e-10
variable fs2s equal 1.0e-15
variable convert equal {atm2Pa}*{atm2Pa}{fs2s}*{A2m}{A2m}*{A2m}

units real

atom_style full

dimension 3

boundary p p p

#The SPC/E water potential
pair_style lj/cut/coul/long 12 12
kspace_style ewald 1.0e-4
pair_coeff 1 1 0.15535 3.1533
pair_coeff * 2 0.00000 0.0000
bond_style harmonic
angle_style harmonic
read_data data.lammps
bond_coeff 1 100.00 1.000
angle_coeff 1 100.00 109.47
#special_bonds lj/coul 0.0 0.0 0.5

group water type 2 3
group graphite type 1

neighbor 2.0 bin
neigh_modify every 1 delay 0 check yes

timestep ${dt}
thermo $d
variable v equal vol
print “volume: $v”

fix RigidOHBonds water shake 0.0001 20 0 b 1 a 1
fix freeze graphite setforce 0.0 0.0 0.0

velocity water create 260 4928459 rot yes mom yes dist gaussian
velocity graphite create 260 4928459 dist gaussian
fix ensemble water nvt temp $T $T 10 drag 0.2

compute tgraph graphite temp
compute twater water temp
thermo_style custom step temp c_tgraph c_twater pe etotal press vol density
thermo 10

#unfix NVT
fix NVE all nve
reset_timestep 0
variable p equal 1000 # correlation length
variable s equal 2 # sample interval
variable d equal $p*$s # dump interval

compute force water group/group graphite
variable fxy equal fxy
variable fxz equal fxz
variable fyz equal fyz

fix SS all ave/correlate $s $p d & v_fxy v_fxz v_fyz type auto file vis.dat ave running variable scale equal {convert}/(${kB}$T)$V*s*{dt}
variable la11 equal trap(f_SS[3]){scale} variable la22 equal trap(f_SS[4])*{scale}
variable la33 equal trap(f_SS[5])
${scale}
variable la equal (v_la11+v_la22+v_la33)/3.0

variable ndens equal count(all)/vol
thermo_style custom step temp press v_fxy v_fxz v_fyz v_la11 v_la22 v_la33 v_la
print “average frictioncoeffient”

Run the simulation

run 900000

i want to calculate friction between water and graphite...

so is there a question here?
please note, that this mailing list is not a "debug my input file"
service. you can (and should) do that on your own.

http://lammps.sandia.gov/doc/Section_errors.html

axel.