We present helium atom scattering experiments from the vitreous silica surface. Time-of-flight data of scattered He-atoms have been recorded at varying temperature and as a function of parallel momentum transfer. A dominant elastic peak and two broad features at ≈ 4 meV, one each on the phonon annihilation and creation side, are observed in all spectra. The thermal measurements between 127.0 an...

The mean-square relative displacements ~MSRD! of atomic pair motions in crystals are studied as a function of pair distance and temperature using the atomic pair distribution function ~PDF!. The effects of the lattice vibrations on the PDF peak widths are modelled using both a multi-parameter Born–von Karman ~BvK! force model and a single-parameter Debye model. These results are compared to exp...

This is the first of a series of five papers in which the thermodynamic properties of minerals are interpreted in terms of lattice vibrational spectra. In this paper, measured heat capacities for minerals are examined in terms of the Debye theory of lattice vibrations, and it is demonstrated that heat capacities of silicates show large deviations from the behavior expected from Debye theory. Th...

Due to its intriguing thermal and electrical properties, graphene has been widely studied for potential applications in sensor and energy devices. However, the reported value for its thermal conductivity spans from dozens to thousands of W m(-1) K(-1) due to different levels of alternations and defects in graphene samples. In this work, the thermal diffusivity of suspended four-layered graphene...

The elastic anisotropy and thermodynamic properties of the recently synthesized Pnnm-CN have been investigated using first-principles calculations under high temperature and high pressure. The calculated equilibrium crystal parameters and normalized volume dependence of the resulting pressure agree with available experimental and theoretical results. Within the considered pressure range of 0-90...

We calculate the Debye and Meissner masses of a gauge boson in a material consisting of two species of massless fermions that form a condensate of Cooper pairs. We perform the calculation as a function of temperature, for the cases of neutral Cooper pairs and charged Cooper pairs, and for a range of parameters including gapped quaisparticles, and ungapped quasiparticles with both quadratic and ...

Polyakov loop correlations at finite temperature in two-flavor QCD are studied in lattice simulations with the RG-improved gluon action and the clover-improved Wilson quark action. From the simulations on a 163 × 4 lattice , we extract the free energies, the effective running coupling geff(T ) and the Debye screening mass mD(T ) for various color channels of heavy quark−quark and quark−anti-qua...