stabilization of graphene sheet

Dear lammps user

Hello

I want to simulate nanoindentation on monolaer graphene.

But I can find some problem that the graphene sheet is not stable at al.

I cannot fix this problem. I appriciate if you can help me solving this problem.

Here below is my scripts.

Thanks in advanced.

---------------------------- INITIALLIZE --------------------------------

units metal

dimension 3

boundary s s s

atom_style atomic

--------------------------- ATOM DEFINITION -----------------------------

#—GRAPHENE

lattice custom 2.4595 &

a1 1 0 0 &

a2 0 1.732050807569 0 &

basis 0 0 0 &

basis 0.5 0.16666666667 0 &

basis 0.5 0.5 0 &

basis 0.0 0.66666666667 0

region simulationbox block 0 200 0 200 -20 26 units box

create_box 2 simulationbox

region graphene block 0 200 0 200 0 1 units box

create_atoms 1 region graphene

group monolayer region graphene

#fix 9 monolayer setforce 0.0 0.0 0.0 region graphene

velocity monolayer

region fixed cylinder z 100 100 90 -20.0 30.0 side out units box

group fixedgr region fixed

fix 2 fixedgr rigid/nvt group 1 fixedgr temp 300.0 300.0 0.01

#—INDENTER

lattice diamond 3.57

region indenter sphere 100.0 100.0 26.0 16.0 units box

create_atoms 2 region indenter

group indent region indenter

fix 4 indent rigid/nvt group 1 indent temp 300.0 300.0 0.01

mass 1 12.01

mass 2 12.01

velocity all create 300.0 100000

----------------------------- FORCE FIELD -------------------------------

pair_style hybrid tersoff lj/cut 0.1

pair_coeff * * tersoff SiC.tersoff C C

pair_coeff 1 2 lj/cut 2.964 3.407

neighbor 2.0 nsq

neigh_modify every 10 check yes

----------------------------- INDENTATION -------------------------------

#velocity all create 300.0 100000

#timestep 0.005

thermo 100

thermo_style custom step temp ke pe etotal

thermo_modify norm no

fix 3 all nvt temp 300.0 300.0 1.0

fix 5 indent move wiggle 0.0 0.0 -5.0 500.0 units box

fix 3 all nvt temp 300.0 300.0 1.0

dump graphene all atom 100 gra_indent_ja8.dump

run_style verlet

run 160000

unfix 5

Why is that you don’t have periodicity on the layer plane?

Carlos

In addition, first take away the pair_hybrid and unnecessary indenter group definitions and just verify you can get a stable graphene sheet with Tersoff. If you don’t get one, simplify the input script even more. Only add in more stuff after a stable sheet is obtained with the pair_style.

Ray