Environmental Engineering Reference
In-Depth Information
NL=1
NL=2
NL=3
NL=4
NL=5
Figure 1.6
Impacts of the number of heat bath layers (NL) on thermal
properties of SiNWs. (a) Temperature profile with different NL of Nose-
Hoover heat bath. (b) Temperature profile with different NL of Langevin
heat bath. (c) Heat flux
J
versus NL. (d) Thermal conductivity
κ
versus NL.
in thermal transport and essentially originated from the specific
geometrical configuration of the edge region [34], very similar
to the electronic and/or spin edge states [35-37]. It should be
emphasized that localization effect is a quite generic consequence
of the breaking of spatial periodicity due to the imposed boundary
condition in finite system. Therefore, LEM also exists with other
boundary conditionsin finitesystem (e.g., free or periodic) [33].
Duetothelocalization,LEMcontributeslittletoheattransport.If
heat bath is applied to this region, LEM will be excited and localized
at this region, while other modes can propagate and contribute to
the heat transport. We can see from Eqs. 1.25 and 1.26 that in order
tomaintainaconstanttemperature,themechanismofNHheatbath
istointroduceaviscosityforce,whichisproportionaltothevelocity,
and the proportionality is determined from the velocities of all the
particles. Due to this deterministic characteristic of NH heat bath,
once LEM is excited, it will accumulate at the heat bath layer over
time, because LEMs have a larger amplitude than other modes and
