| Home | Introduction
| Approach & Model | Computational
Process | Calculation of Electric Field | Results
& Discussions | References & Appendix |
Results and Discussions:
Nanotube Growth: No electric field
present
Below is the simulation of nanotube
growth. We find that the ethylene partial pressure has a linear
effect on the growth rate of the nanotube. It also has a more
subtle effect on the shape of the growing end of the nanotube. This type
of effect, while not likely to be observable, could provide significant insight
into why/how nanotubes of different size and chiralty are formed.
For source code click here.
Download movie
click here.
Nanotube Growth: Electric field is
present
Next we explored the impact of applying an
electric field during nanotube growth. For large enough applied
potentials, the growth rate can be slowed down or hastened by changing the
bias. For a perfectly flat-ended nanotube, this would induce a uniform
field and therefore, a uniform force. However, because of the curved
nature of the nanotube, the force varies along the contour the of the
tube. This has a subtle impact over the initial growth
shape, while at larger tube lengths, this effect diminishes. Again, this
type of effect, while not likely to be observable, could provide significant
insight into how nanotubes of different sizes and chiralties are
initiated. For example, at high negative field, the growth is strongly
suppressed, resulting in a rounder nanotube initially. This could result
in a less chiral nanotube (such as the folding chair structure).
Lastly, we plot the Field-Driven Forces
for two different biases to clearly show how the CN experiences different
field-induced stresses, altering the shape, and thus altering the shape of the
electric field force. At the beginning of the movie, the forces are the same
shape just opposite in sign; by the end of the movie the forces clearly no
longer have the same shape (if you were to flip the sign on one of them).
Also the enhanced growth rate with
positive bias is in agreement with observed phenomena where CNTs tend to grow
preferentially towards positive electrodes.
For source code click here.
Negative
Field
Download movie
click here.
Positive
Field
Download movie
click here.
Comparison of Field-Driven Forces (Overlaid on CNT Growth)
Download movie
click here.