Thermal conductivity spectroscopy technique to measure phonon mean free paths.

Size effects in heat conduction, which occur when phonon mean free paths (MFPs) are comparable to characteristic lengths, are being extensively explored in many nanoscale systems for energy applications. Knowledge of MFPs is essential to understanding size effects, yet MFPs are largely unknown for most materials. Here, we introduce the first experimental technique which can measure MFP distributions over a wide range of length scales and materials. Using this technique, we measure the MFP distribution of silicon for the first time and obtain good agreement with first-principles calculations.

Why the all-electron full-potential approach is suitable for calculations on fullerenes and nanotubes?

Already 30 years have passed since the first prediction of C60 by Professor Osawa. A family of cage-type fullerenes and carbon nanotubes were experimentally found as the third form of carbon molecules in the 1980s. After this discovery, much research has been conducted experimentally and theoretically on these new materials. The all-electron full-potential approach is important for fully understanding the quantum mechanical behavior of the fullerenes and related molecules. We show some results of band calculations and ab initio molecular dynamics.