Environmental Engineering Reference
In-Depth Information
Figure 1.9
ImpactsofheatbathparameteronthermalpropertiesofSiNWs.
Thenanowirehasafixedcross-sectionof3
×
3unitcells.Inthelongitudinal
direction, it has a fixed length of 10 unit cells with three layers of heat bath
ateachend.(a)Temperatureprofilewithparameter
τ
ofNose-Hooverheat
bath. (b) Temperature profile with parameter
of Langevin heat bath. (c)
Heat flux
J
versus heat bath parameter. (d) Thermal conductivity
λ
κ
versus
≤
τ
≤
≤
λ
≤
heat bath parameter. Here 0.05
1000,and 0.1
400.
290 K, and tune the heat bath parameters to study their impacts on
heat flux, temperature profile, and thermal conductivity.
Next we set NL
=
3 for both NH and Langevin heat bath. In Fig.
1.9 we plot the impacts of heat bath parameter on the calculated
thermalpropertiesofSiNWs.ForNHheatbath,
τ
cannotbetoosmall
(e.g.,
τ
=
0.01 in Fig. 1.9a) since it produces wrong temperature
profile in this case, although the heat bath still can reach the aimed
temperature and a temperature gradient can be established in the
middle region. With the increase of
τ
from 0.01, the temperature
gradient in the middle region is almost the same, but the mean
temperature decreases until
τ
=
0.2. This results in a decrease in
heat current when
0.04, TJ at the
left boundary is nearly zero, while TJ at the right boundary is about
5 K. This should be a numerical artifact because TJ has its physical
τ<
0.2. Particularly when
τ
=
