Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
MD Simulations of the Tensile Strength of (20,0) Single Walled Carbon Nanotubes
Gülay Dereli, * Necati Vardar and
Department of Physics, Yildiz Technical University, 34210, Turkey
Abstract— We have performed a computer experiment to examine the stability of (20,0) Single Walled Carbon Nanotubes (SWCNTs) with the
application of uniaxial strain. A (20,0) single-walled carbon nanotube consisting of 400 atoms with 20 layers is simulated under tensile loading
using our developed O(N) parallel tight-binding molecular-dynamics algorithms. It is observed that the simulated carbon nanotube is able to carry
the strain up to 118 % of the relaxed tube length in elongation. In this study, the elastic limit, Poisson ratio, Young’s modulus and tensile strength
of (20,0) SWCNTs are calculated.
There has been increasing attention given to Single-Walled
Carbon Nanotubes (SWCNTs) since they are the most durable
material against stretching and heating. SWCNTs properties
are mostly determined by the chirality of the tubes. Depending
on their chirality, carbon nanotubes could be metal or
semiconductor. Durability of the nanotubes are examined in
terms of the uniaxial compressive or tensile deformations.
Single Walled Carbon Nanotubes are specified by chiral
vector Ch
( n, m)
.The Zigzag SWCNTs that are represented
as (n,0) are metallic, if n is a multiple of 3 and all other are
semiconducting in unstrained condition.
In this study, we have performed a computer experiment to
examine structural stability and mechanical properties of
(20,0) SWCNT under tensile loading. Deformations due to
uniaxial strain are studied using a parallel, Order (N) tightbinding
molecular dynamics (O(N) TBMD) simulation code.
Parallel O(N) (TBMD) simulation code is designed by
G.Dereli et al.[1-3] and applied successfully to SWCNTs
simulations[4-7].
A semiconducting (20,0) SWCNT consisting of 400 atoms
with 20 layers is simulated. Periodic boundary condition is
applied along the tube axis. Velocity Verlet algorithms along
with the canonical ensemble molecular dynamics (NVT) is
used. In our simulation procedure (20,0) SWCNT is simulated
at a specified temperature for a 3000 MD steps of run with a
time step of 1 fs. This eliminates the possibility of the system
to be trapped in a metastable state. We wait for the total
energy per atom to reach the equilibrium state. Next, uniaxial
strain is applied to the SWCNT. We further simulate the
deformed tube structure under uniaxial strain for another 2000
MD steps. In our study, while the nanotube is axially
elongated or contracted, reduction or enlargement of the radial
dimension is observed. Strain is obtained from ( LL0)/
L0
where L
0
and L are the tube lengths before and after the
strain, respectively. We applied the elongation and calculated
the average total energy per atom. Following this procedure,
we examined the structural stability, total energy per atom,
stress-strain curves, elastic limit, Young’s modulus, tensile
strength, and Poisson ratio of (20,0) SWCNT. Deformations
affect the physical properties of SWCNTs.
We calculated the total energy of (20,0) SWCNTs as -8.29582
eV at zero strain. Figure 1, shows the total energy per atom of
(20,0) SWCNT as a function of simulation time. On
application of uniaxial strain, the total energy values have
changed. Figure 2, gives the total energy values for various
strain values.
Our studies show that (20,0) SWCNT is stable until 18%
uniaxial strain value. Figure 3 indicates that the tube can not
sustain its structural stability at 23% strain. Beyond these
strain values, bond breakings between the carbon atoms are
observed and the tube is no longer stable. Stability of (20,0)
SWCNT is compared with the same number of atom but
smaller diameter SWCNTs during the study.
E (eV/atom)
-8,27
-8,28
-8,29
-8,30
-8,31
-8,32
-8,33
-8,34
0 500 1000 1500 2000 2500 3000
MD Step
Figure 1: Total energy of (20,0) SWCNT as a function of simulation
time
E (eV/atom)
-6,8
-7,2
-7,6
-8,0
0
1
2
3
4
5
6
7
8
9
12
15
18
21
23
(20,0)
-8,4
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
MD Step
Figure 2: The effect of strain on the total energies of (20,0) SWCNTs
as a function of simulation time.
Figure 3: Simulation picture of (20,0) SWCNT under % 23 uniaxial
strain
The research reported here is supported through the Yildiz
Technical University Research Fund Project No: 24-01-01-04.
The simulations are performed at the Carbon Nanotubes
Simulation Laboratory at the Department of Physics, Yildiz
Technical University, Istanbul, Turkey.
*Corresponding author: gdereli@yildiz.edu.tr
148, 188
(2002).
[2] G. Dereli and C. Özdogan, Phys. Rev. B 67, 035416 (2003).
[3] G. Dereli and C. Özdogan, Phys. Rev. B 67, 035415 (2003).
[4] G. Dereli and B. Süngü, Phys. Rev. B 75, 184104 (2007).
[5] G. Dereli, B. Süngü and C. Özdogan, Nanotechnology 18, 24570 (2007).
20 ,
075707 ( 2009)
171 (2010).
(20,0)
6th Nanoscience and Nanotechnology Conference, zmir, 2010 397