Wc develop the embedded-atom method [Phys. Rev. Lett. 50, 1285], based on densityfunctional theory, as a new means of calculating ground-state properties of realistic metal systems. %'e derive an expression for the total energy of a metal using the embedding energy from which we obtain. several ground-state properties, such as the lattice constant, elastic constants, sublimation energy, and vacancy-formation energy. We obtain the embedding energy and accompanying pair potentials semiempirically for Ni and Pd, and use these to treat several problems: surface energy and relaxation of the (100), (110), and (111)faces; properties of H in bulk metal (H migration, binding of H to vacancies, and lattice expansion in the hydride phase); binding site and adsorption energy of hydrogen on (100), (110), and (111)surfaces; and lastly, fracture of Ni and the effects of hydrogen on the fracture. We emphasize problems with hydrogen and with surfaces because none of these can be treated with pair potentials. The agreement with experiment, the applicability to practical problems, and the simplicity of the technique make it an effective tool for atomistic studies of defects in metals.

No abstract

No abstract

Contents 1. Introduction 2. Embedded-atom method 2.1. Fundamentals 2.2. Phenomenology 2.3. Empiricism 3. Overview of applications 4. Bulk properties 4.1. Bulk phonons 4.2. Liquids 4.3. Thermal expansion, melting, and thermodynamic functions 4.4. Point defects 5. Grain boundaries 5.1. Structure 5.2. Role of many-body interactions 5.3. Elastic properties of grain boundaries 5.4. Thermal effects at grain boundaries 6. Surfaces 6.1. Surface energies and relaxations 6.2. Surface phonons 6.3. H/Pd(lll) 6.4. Au and Pt(ll0)-(1 × 2) 6.5. Adatom clusters on Pt(001) 7. Alloys 7.1. Dilute surface segregation 7.2. Bond breaking (surface segregation in Ni-Cu) 7.3. Compositional ordering 7.3.1. Example of short-range order: surface segregation in Pd-noble-metal alloys 7.3.2. Example of long-range order: surface segregation in Cu-Au alloys 7.3.3. Loss of long-range order: segregation to grain boundaries in Ni3AI 7.4. Segregation in strain fields 7.4.1. Segregation to a sessile edge dislocation 7.4.2. Segregation to (001) twist boundaries in Ni-Cu 7.4.3. Segregation to (001) twist boundaries in Pt-1 at.% Au alloys 8. Mechanical properties

Described herein are initial experimental details and properties of a silicon core, silica glass-clad optical fiber fabricated using conventional optical fiber draw methods. Such semiconductor core fibers have potential to greatly influence the fields of nonlinear fiber optics, infrared and THz power delivery. More specifically, x-ray diffraction and Raman spectroscopy showed the core to be highly crystalline silicon. The measured propagation losses were 4.3 dB/m at 2.936 microm, which likely are caused by either microcracks in the core arising from the large thermal expansion mismatch with the cladding or to SiO(2) precipitates formed from oxygen dissolved in the silicon melt. Suggestions for enhancing the performance of these semiconductor core fibers are provided. Here we show that lengths of an optical fiber containing a highly crystalline semiconducting core can be produced using scalable fiber fabrication techniques.

No abstract

No abstract

The embedded atom method [M. S. Daw and M. I. Baskes, Phys. Rev. B 29, 6443 (1984) used to calculate phase stability, lattice vibrational frequencies, point defect properties, antiphase boundary energies, and surface energies and relaxations for Ni3Al. The empirical embedding functions and core-core repulsions used by this method are obtained. The equilibrium phases for the Ni-rich half of the composition range of Ni–Al are determined for 1000 K and compared with experiment. The elastic constants and vibrational modes of Ni3Al are calculated and the elastic constants are compared with experiment. The formation energy, formation volume, and migration energies of vacancies are computed, and it is found that the formation energy of vacancies on the Ni sublattice is less than that on the Al sublattice. The (100) antiphase boundary is shown to be significantly lower in energy than the (111) antiphase boundary. The surface energies and atomic relaxations of the low index faces are computed, and it is shown that for the (100) and (110) faces that the preferred surface geometry corresponds to the bulk lattice with the mixed composition plane exposed.