Biomedical Engineering Reference
In-Depth Information
Fig. 1.13
(
a
) Water density distributions along
z
(carbon nanotube axis). (
b
) Water density
distributions inside the nanotube together with the positions of the carbon atoms. The
red
and
black
filledcircles
denote the positions of the carbon atoms. The
arrow
,markedby
P
, is the position of
the atom affected by an external force (reprinted from [
129
]. Copyright 2008 American Physical
Society)
wavelike pattern increases obviously, but the distances between crests and troughs
change very little, almost fixed. For 1:5 < ı
6
ı
c
2:0 A, the amplitude of the
wavelike pattern increases sharply. From ı
2:0 A and up, the wavelike pattern
of the water density distribution was deformed and the density at
P
is smaller than
that of the other parts. For ı
>
2:5 A, the density distribution at
P
is very close to
zero. Outside the CNT, the water density distribution is not affected by the shape of
the CNT. There are two peaks near the two openings of the CNT due to the van der
Waals (VDW) attraction of two graphite sheets.
The average number of water molecules inside the CNT of 13.4 A is about five.
For the CNT of 14.6 A, the average number of water molecules inside the nanotube
is about 5.5. The number of water molecules inside the CNT fluctuates with respect
to time (see Fig.
1.14
). There are two stable states with
N
D
5and
N
D
6. The system
switches mainly between the two states. The average durations for the states with
