# Regarding graphene thermal conductivity

Dear all LAMMPS users,

While I am running the lammps code for the evaluation of thermal conductivity of Graphene I am facing an error like "Divide by 0 in variable formula. I would like to know the reason and How can fix the problem. Please refer the input script here below.

variable T equal 300
variable V equal vol
variable dt equal 0.001
#variable p equal 1000 # correlation length
#variable s equal 5 # 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 eV2J equal 1.602e-19
variable A2m equal 1.0e-10
variable ps2s equal 1.0e-12
variable convert equal {eV2J}*{eV2J}/{ps2s}/{A2m}
variable alat equal 2.46

# setup problem

units metal
boundary p p p
atom_style atomic

mass 1 12.0

pair_style tersoff
pair_coeff * * /home/kpark39/programs/lammps-1Feb14/potentials/SiC_1994.tersoff C
neighbor 2.0 bin
neigh_modify delay 5
timestep \${dt}

variable tmp equal lx
variable lo equal \${tmp}
variable strain equal (lx-v_lo)/v_lo

variable p1 equal “-pxx/10000”
variable p2 equal “-pyy/10000”

# 2nd equilibration run

compute ke all ke/atom

# units of Kb = J/K, units of ke = eV or J, so temp becomes K

variable temp atom c_ke*{eV2J}/(1.5*{kB})
fix 1 all nve
compute cc1 all chunk/atom bin/1d x lower 5
fix 2 all ave/chunk 10 100 1000 cc1 v_temp file profile.mp #units box

fix 3 all thermal/conductivity 10 x 190 swap 2
fix 4 all temp/berendsen 300 300 100
variable tdiff equal f_2[96][3]-f_2[1][3]

# thermal conductivity calculation

fix 5 all ave/time 1 1 1000 v_tdiff ave running file ave.dat
variable Z equal f_3*{eV2J}*1000/2/(110*3.4)/{A2m}/{dt}/100000/{ps2s}/f_5
fix 7 all deform 1 x erate 0.0001 units box
fix def all print 1000 “{strain} {p2} \${p1}” file Graphene_tensile_data_300K.txt
dump 7 all custom 5000 Graphene_thermal_deform*.lammpstrj id type x y z
thermo_style custom step temp epair etotal f_3 v_tdiff f_5 v_Z
thermo 1000

run 100000

Dear all LAMMPS users,

While I am running the lammps code for the evaluation of thermal
conductivity of Graphene I am facing an error like "Divide by 0 in variable
formula. I would like to know the reason and How can fix the problem.
Please refer the input script here below.

the reason is what the error message says it is: in one of your
variable expressions you have a division by zero which causes LAMMPS
to abort.
this is fixed by a process called "debugging": you need to check your
input line by line for which line may be causing this issue.

BTW: it looks like you are using a 4 year old version of LAMMPS. that
is not a good idea. there was just a new stable release. you should
upgrade to that one. as a bonus, you may get some help from that
LAMMPS version to identify which variable expression is failing.

axel.