The project aims at developing path integral calculations for the computation of heat conductovity in insulating solids, taking quantum effects into account automatically. First for crystals, then for amorphous systems or nanostructures.
Heat transport in materials is a key property for a number of applications, and significant efforts are devoted to the design of materials with high (for heat transport applications) or low (e.g., for <br />thermoelectric conversion) heat conductivity, . With the exception of good metallic conductors, <br />thermal conductivity is in general dominated by atomic vibrations. The goal of the present project is <br />to establish a methodology for determining the vibrational contribution to thermal conductivities of <br />materials, using the formalism of path integrals that allows one to take into account accurately nuclear <br />quantum effects (NQE) in condensed systems.
The calculations will be based on Kubo formulae that involve time correlation functions to obtain th etransport coefficients. The corresponding correlations can be computed in imaginary time using the PIMC approach. The challenge is to obtain them witj good enough accuracy, so that teh Fourier spectrum can be obtained from imaginary time data. The present approach is to use a maximum entropy method to achieve this aim.
At the moment the method has been applied with success to a toy model (harmonic oscillator). The results appear to be convincing, we hope th emethod will be applicable to more complex cases.
Benchmark onf the method for a toy model.
Perspective: publication of results for the toy model, application to a more complex crystal.
Papers are not ready yet.
The goal of the project HeatFlow is to establish a methodology, based on the formalism of path integrals, allowing one to accurately take into account the influence of nuclear quantum effects on transport properties, and in particular heat transport, in condensed systems. This is a very ambitious task which, be believe, would have profound implications in many research fields, ranging from fundamental physics issues to the development of advanced materials for modern technological applications. We plan to apply the methodology we will develop to a few case studies, involving systems of both fundamental and practical interest in condensed matter science. In particular, we will focus, on one side,
on amorphous systems (glasses) and try to clarify in a plainly first-principles calculations framework the origin of the striking low-temperature anomalies in the thermal properties. On the other side, more in perspective and moving to systems of increased complexity, we will in contrast focus on highly ordered nano-structures, where a careful design with very high spatial resolution can trigger remarkable thermal responses.
Monsieur Jean-Louis Barrat (Laboratoire Interdisciplinaire de Physique)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
SyMMES Systèmes Moléculaires et nano Matériaux pour l'Energie et la Santé
LPMMC LABORATOIRE DE PHYSIQUE ET MODELISATION DES MILIEUX CONDENSES
LIPHY Laboratoire Interdisciplinaire de Physique
Help of the ANR 346,597 euros
Beginning and duration of the scientific project: December 2018 - 48 Months