Environmental Engineering Reference
In-Depth Information
Figure 1.20
Cross-sectional view of SiNTs with central atoms (smaller
circles) denoting the removed atoms.
In this simulation, SW potential is used to derive the force term.
Numerically, a velocity Verlet algorithm is employed to integrate
Newton's equations of motion, and each MD step is set as 0.8 fs.
A cubic supercell of
N
X
×
N
Y
×
N
Z
unit cells is used. A periodic
boundary condition is applied in the
x
(longitudinal) direction, and
a free boundary condition is applied in the other two directions,
the atoms on the inner and outer surfaces of SiNTs and SiNWs.
For each realization, all the atoms are initially placed at their
equilibrium positions but have a random velocity according to
Gaussian distribution. Canonical ensemble MD with Langevin heat
reservoir first runs for 10
5
steps to equilibrate the whole system
at a given temperature. Then microcanonical ensemble MD runs
for another 3
10
6
steps (2.4 ns) and heat current is recorded at
each step. After that, thermal conductivity is calculated according
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