Optical properties of In2O3 from experiment and first-principles theory: influence of lattice screening

The framework of many-body perturbation theory led to deep insight into electronic structure and optical properties of diverse systems and, in particular, many semiconductors. It relies on an accurate approximation of the screened Coulomb electron–electron interaction W, that in current implementations is usually achieved by describing electronic interband transitions. However, our results for several oxide semiconductors indicate that for polar materials it is necessary to also account for lattice contributions to dielectric screening. To clarify this question in this work, we combine highly accurate experimentation and cutting-edge theoretical spectroscopy to elucidate the interplay of quasiparticle and excitonic effects for cubic bixbyite In2O3 across an unprecedentedly large photon energy range. We then show that the agreement between experiment and theory is excellent and, thus, validate that the physics of quasiparticle and excitonic effects is described accurately by these first-principles techniques, except for the immediate vicinity of the absorption onset. Finally, our combination of experimental and computational data clearly establishes the need for including a lattice contribution to dielectric screening in the screened electron–electron interaction, in order to improve the description of excitonic effects near the absorption edge

Dielectric function and critical points of the band structure for hexagonal and cubic GaN and AlN

weitere beteiligte Personen: Dr. Andreas Hangleiter Stefan Potthast Donald J. A

Intel Paragon XP/S - Architecture and Software Environment

The paper describes the hardware and software components of the Intel Paragon XP/S system, a distributed memory scalable multicomputer. The Paragon processing nodes, which are based on the Intel i860 XP RISC processor, are connected by a two-dimensional mesh with high bandwidth. This new interconnection network and the new operating system are the main differences between the Paragon and its predecessor, the iPSC/860 with its hypercube topology. The paper first gives an overview of the Paragon system architecture, the node architecture, the interconnection network, I/O interfaces, and peripherals. The second part outlines the Paragon OSF/1 operating system and the program development environment including programming models, compilers, application libraries, and tools for parallelization, debugging, and performance analysis

A catalog of classifying characteristics for massively parallel computers

In order to facilitate an application-oriented assessment of high-performance massively parallel computing systems, a catalog of about 350 classifying characteristics concerning the architecture and software environment of such systems has been compiled. The data required for the catalog allow a rather complete and homogeneous description of a massively parallel system to be established. This article contains an overview of the catalog and the hardware model on which it is based