Abstract
A crucial goal for increasing thermal energy harvesting will be to progress towards atomistic design strategies for smart nanodevices and nanomaterials. This requires the combination of computationally efficient atomistic methodologies with quantum transport based approaches. Here, we review our recent work on this problem, by presenting selected applications of the PHONON tool to the description of phonon transport in nanostructured materials. The PHONON tool is a module developed as part of the Density-Functional Tight-Binding (DFTB) software platform. We discuss the anisotropic phonon band structure of selected puckered two-dimensional materials, helical and horizontal doping effects in the phonon thermal conductivity of boron nitride-carbon heteronanotubes, phonon filtering in molecular junctions, and a novel computational methodology to investigate time-dependent phonon transport at the atomistic level. These examples illustrate the versatility of our implementation of phonon transport in combination with density functional-based methods to address specific nanoscale functionalities, thus potentially allowing for designing novel thermal devices.
Highlights
The accelerated pace of technological advances, which has taken place over the last half-century, has driven the continuous search for higher speed and cheaper computing with the concomitant developments of larger integration densities and miniaturization trends based on novel materials and processes [1]
We address selected applications of our recent implementations of quantum transport methodologies in low-dimensional materials
We combined the non-equilibrium Green’s functions (NEGF) formalism with the Density-Functional Tight-Binding (DFTB) methodology to address quantum ballistic transport in various low-dimensional materials with atomistic resolution. This computational approach is implemented as a tool in the DFTB+ software. These systems may be tractable using classical molecular dynamics, extensive parameterizations may be required to study different material combinations
Summary
The accelerated pace of technological advances, which has taken place over the last half-century, has driven the continuous search for higher speed and cheaper computing with the concomitant developments of larger integration densities and miniaturization trends based on novel materials and processes [1]. While considerable progress has been achieved in nanoelectronics in the implementation of local electrodes and gates over very short length scales, establishing temperature gradients over nanoscopic length scales remains a considerable challenge In this respect, for characterizing thermal devices, novel sophisticated experimental techniques have been developed, such as the 3ω method [20] and the frequency domain thermoeflectance [21], pioneered by Cahill et al [22]. The last category covers methodologies relying on the Landauer approach, or more generally on non-equilibrium Green’s functions (NEGF) [32,33,34,35] All these methodologies have found extensive application in the prediction of the thermal transport properties of various low-dimensional materials, yielding correct trends and results in good agreement with experimental studies [36,37,38]. This methodology is illustrated for a one-dimensional chain and simple nanoscale junctions based on polyethylene and polyacetylene dimers
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