DSpace Community:
http://hdl.handle.net/10261/46
2016-07-29T17:58:26ZHeat transport through a solid–solid junction: the interface as an autonomous thermodynamic system
http://hdl.handle.net/10261/135085
Title: Heat transport through a solid–solid junction: the interface as an autonomous thermodynamic system
Authors: Rurali, Riccardo; Colombo, Luciano; Cartoixà, Xavier; Wilhelmsen, Øivind; Trinh, Thuat T.; Bedeaux, Dick; Kjelstrup, Signe
Abstract: We perform computational experiments using nonequilibrium molecular dynamics simulations, showing that the interface between two solid materials can be described as an autonomous thermodynamic system. We verify the local equilibrium and give support to the Gibbs description of the interface also away from the global equilibrium. In doing so, we reconcile the common formulation of the thermal boundary resistance as the ratio between the temperature discontinuity at the interface and the heat flux with a more rigorous derivation from nonequilibrium thermodynamics. We also show that thermal boundary resistance of a junction between two pure solid materials can be regarded as an interface property, depending solely on the interface temperature, as implicitly assumed in some widely used continuum models, such as the acoustic mismatch model. Thermal rectification can be understood on the basis of different interface temperatures for the two flow directions.2016-07-27T11:34:20ZBand gap engineering of MoS2 upon compression
http://hdl.handle.net/10261/135081
Title: Band gap engineering of MoS2 upon compression
Authors: López-Suárez, Miquel; Neri, Igor; Rurali, Riccardo
Abstract: Molybdenum disulfide (MoS2) is a promising candidate for 2D nanoelectronic devices, which shows a direct band-gap for monolayer structure. In this work we study the electronic structure of MoS2 upon both compressive and tensile strains with first-principles density-functional calculations for different number of layers. The results show that the band-gap can be engineered for experimentally attainable strains (i.e., ±0.15). However, compressive strain can result in bucking that can prevent the use of large compressive strain. We then studied the stability of the compression, calculating the critical strain that results in the on-set of buckling for free-standing nanoribbons of different lengths. The results demonstrate that short structures, or few-layer MoS2, show semi-conductor to metal transition upon compressive strain without bucking.2016-07-27T11:04:23ZThermal rectification in silicon by a graded distribution of defects
http://hdl.handle.net/10261/135080
Title: Thermal rectification in silicon by a graded distribution of defects
Authors: Dettori, Riccardo; Melis, Claudio; Rurali, Riccardo; Colombo, Luciano
Abstract: We discuss about computer experiments based on nonequilibrium molecular dynamics simulations providing evidence that thermal rectification can be obtained in bulk Si by a non-uniform distribution of defects. We consider a graded population of both Ge substitutional defects and nanovoids, distributed along the direction of an applied thermal bias, and predict a rectification factor comparable to what is observed in other low–dimensional Si–based nanostructures. By considering several defect distribution profiles, thermal bias conditions, and sample sizes, the present results suggest that a possible way for tuning the thermal rectification is by defect engineering.2016-07-27T10:31:54ZThermal transport in porous Si nanowires from approach-to-equilibrium molecular dynamics calculations
http://hdl.handle.net/10261/135047
Title: Thermal transport in porous Si nanowires from approach-to-equilibrium molecular dynamics calculations
Authors: Cartoixà, Xavier; Dettori, Riccardo; Melis, Claudio; Colombo, Luciano; Rurali, Riccardo
Abstract: We study thermal transport in porous Si nanowires (SiNWs) by means of approach-to-equilibrium
molecular dynamics simulations. We show that the presence of pores greatly reduces the thermal
conductivity, j, of the SiNWs as long mean free path phonons are suppressed. We address explicitly
the dependence of j on different features of the pore topology—such as the porosity and the pore
diameter—and on the nanowire (NW) geometry—diameter and length. We use the results of the
molecular dynamics calculations to tune an effective model, which is capable of capturing the
dependence of j on porosity and NW diameter. The model illustrates the failure of Matthiessen’s
rule to describe the coupling between boundary and pore scattering, which we account for by the
inclusion of an additional empirical term.2016-07-26T11:46:51Z