Phonon Green’s function -Towards a super tool for thermomechanical modeling of nanomaterials

A multiscale Green’s function method, developed at NIST, Boulder, over the last several years, will be described for modeling the thermomechanical properties of nanomaterials, especially semiconductors. It is a problem of strong topical interest because of its application to modern solid-state devices. Static as well as phonon Green’s function-based methods will be discussed. These methods are based upon the continuum as well as discrete lattice models of solids. The method fully accounts for the nonlinear discrete lattice effects in the near-field and reduces asymptotically to the macroscopic continuum model in the far-field region. A major advantage of the lattice Green’s function method is that it can model a large crystallite containing, for example, a million atoms without excessive computational effort and it links nanoscales seamlessly to macroscales. Our primary interest at NIST is in the measurement science and setting up of standards.  Any process of measurement on a system involves a probe and the measurable response of the system to the probe. The response of the system is the Green’s function. Hence, it is also called the response function. Thus, the Green’s function is basically a measurement tool.  

 

Calculation of the Green’s function requires a detailed knowledge of the materials’ characteristics like interatomic potential, which is subject to many uncertainties.  What makes the Green’s function a possible super-tool, is, that the Green’s function can, in principle, be directly measured. If measured values of the Green’s function can be available, all the modeling problems can be solved. That is the direction in which presently I am working.

 

 

Please email emma.nelson-1@colorado.edu with any questions or to be added to the CU Phonon Club email list!