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Transport in nonlinear chains and across several condensed matter interfaces.

机译：在非线性链中和在多个凝聚态物质界面之间传输。

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摘要

In recent years, with the advances in experimental techniques, the characteristic length scales of the materials synthesized, are becoming increasingly small. Many of these microscopic structures found their places in important commercial applications. However, the thermal loads imposed on these devices and structures create a major obstacle toward their applicability. This challenge is driving a renewed interest among researchers from various disciplines, toward the topic of thermal management. The interest in the topic of thermal transport in small scale structures, served as the motivation for the work performed in this dissertation. More specifically, the following topics were investigated:;• Transport in One-Dimensional Nonlinear Systems: Thermal transport in materials can be explained in terms of the diffusive motion of the heat carriers at the microscopic level. An important and surprising situation emerges in some low dimensional model systems; the thermal conductivity diverges with system size. It was shown (Toda, 1979) that nonlinearity has an important effect on the heat transport in low dimensional systems. We investigate the transport of energy in a nonlinear one-dimensional chain. We show that solitons are spontaneous generated when we apply forcing functions at the end of the chain. We investigate the different characteristics of these solitons generated in the chain.;• Transport in Fluids --- Study of Pair Distribution Function: Thermal transport in fluids depends on the distribution of particles in the fluid. It is well known that the two-particle distribution function can describe most of the thermodynamic properties for classical fluids in thermal equilibrium. We review the approximate integral equation theories (Percus-Yevick, Hypernetted chain approximation) to obtain the pair distribution functions of classical fluids. We find that these methods are highly dependent on the choice of the thermodynamic parameters of the fluid. We solve several Lennard-Jones fluid systems with different density and temperature values and prepare a density-temperature compressibility diagram. This diagram shows the region of applicability of these theories and helps us obtain the pair distribution function for a Lennard-Jones fluid with known thermodynamic parameters. We also suggest a modification of the integral-equation theories to obtain the pair distribution functions of quantum fluids.;• Thermal Transport Across Interfaces: When thermal energy is transported from one material to another, there is a discontinuity in temperature at the interface between them. This thermal boundary resistance is known as Kapitza resistance. The scattering of phonons at interfaces is one of the main reasons behind the presence of thermal boundary resistance. We explore the scattering of acoustic waves at several solid-solid interfaces using lattice dynamical methods. We derive matrix equations to obtain the reflection and transmission coefficients for an acoustic wave incident on the interface. These coefficients can reproduce the familiar expressions in the continuum limit and are consistent with the conservation relations.;We discuss a method to obtain the thermal boundary resistance for neutral solid-fluid interfaces. The acoustic mismatch theory works poorly for solid-fluid interfaces. One reason is that this theory only includes the long wavelength acoustic phonons. Our theory includes all the phonon modes in the solid and all the sound modes in the fluid, in the calculation of the thermal boundary resistance. We provide an application of this method to obtain the thermal boundary resistance at the interface between solid Argon and liquid Neon. Our method yields the value for Kapitza conductance for solid Argon-fluid Neon interface as 0.0374GW/Km2.
机译：近年来，随着实验技术的进步，合成材料的特征长度尺度越来越小。这些微观结构中的许多在重要的商业应用中找到了自己的位置。但是，施加在这些设备和结构上的热负荷对其应用造成了主要障碍。这一挑战正在促使各个学科的研究人员对热管理这一话题重新产生兴趣。对小规模结构中的热传输这一主题的兴趣，成为本文进行工作的动力。更具体地说，研究了以下主题：•一维非线性系统中的传输：材料中的热传输可以用载热体在微观水平上的扩散运动来解释。在某些低维模型系统中出现了一个重要且令人惊讶的情况。导热系数随系统尺寸而变化。研究表明（Toda，1979），非线性对低维系统的热传递有重要影响。我们研究了非线性一维链中的能量传输。我们表明，在链的末端应用强制函数时，孤子是自发生成的。我们研究了链中产生的这些孤子的不同特性。；•流体中的传输---对分布函数的研究：流体中的热传输取决于流体中颗粒的分布。众所周知，两粒子分布函数可以描述热平衡下经典流体的大多数热力学性质。我们回顾了近似积分方程理论（Percus-Yevick，Hypernetted链近似），以获得经典流体的对分布函数。我们发现这些方法高度依赖于流体的热力学参数的选择。我们解决了几种具有不同密度和温度值的Lennard-Jones流体系统，并准备了密度-温度可压缩性图。该图显示了这些理论的适用范围，并帮助我们获得了具有已知热力学参数的Lennard-Jones流体的对分布函数。我们还建议对积分方程理论进行修改，以获得量子流体的对分布函数。；•跨界面的热传输：当热能从一种材料传输到另一种材料时，它们之间的界面处温度不连续。该热边界电阻称为Kapitza电阻。声子在界面处的散射是存在热边界电阻的主要原因之一。我们使用晶格动力学方法探索了声波在多个固体-固体界面的散射。我们导出矩阵方程，以获得入射在界面上的声波的反射系数和透射系数。这些系数可以在连续极限中再现出熟悉的表达式，并且与守恒关系一致。我们讨论了一种获得中性固-液界面热边界电阻的方法。声学失配理论不适用于固体-流体界面。原因之一是该理论仅包括长波长声子。在计算热边界电阻时，我们的理论包括固体中的所有声子模态和流体中的所有声模。我们提供了该方法的应用，以获取固态氩和液态氖之间界面的热边界电阻。我们的方法得出的固体氩流体氖气界面的Kapitza电导值为0.0374GW / Km2。

著录项

  • 作者

    Neogi, Sanghamitra.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Condensed matter physics.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 149 p.
  • 总页数 149
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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