The extended Hubbard Hamiltonian on a bcc lattice is studied at half-filling and for a finite hopping between next-nearest-neighbours, in mean-field approximation. An ionic insulating broken-symmetry phase is predicted for any hydrogenoid bcc solid in the density range 1.0 < r s < 2.6. The occurrence of an ionic phase would explain the failure to achieve hydrogen metallization at high pressures...

plasters are produced from a light refractory material, mainly mgo (m.p. 2800ºc), a binder, and a void forming substance for insulating purposes. different oxides from the slag penetrate into these voids and provide low melting-point phases suchasrhodonite (mnsio3) (1290ºc), tephorite (mn2sio4) (1345ºc), merwinite (ca3mgsi2o8) (1575ºc), monticellite (camgsio4) (1490ºc), and enstatite (mgsio3) (...

We present a study of the electrical properties of insulating CeO2 layers in combination with superconducting ~Y/Dy! Ba2Cu3O72d ~RBCO! films over ramps and in crossover structures. CeO2 is frequently used as a buffer layer, or template layer for biepitaxial grain boundary junctions, but can also be used as an insulating layer in ramp-type junctions and other multilayer structures. Epitaxial thi...

We discuss the rich vibrational dynamics of nanometer-scale semiconducting and insulating crystals as probed by localized electronic impurity states, with an emphasis on nanoparticles that are only weakly coupled to their environment. Two principal regimes of electron–phonon dynamics are distinguished, and a brief survey of vibrationalmode broadening mechanisms is presented. Recent work on the ...

We find that temperature dependent screening can quantitatively explain the metallic behavior of the resistivity on the metallic side of the so-called metal-insulator transition in p-SiGe. Interference and interaction effects exhibit the usual insulating behavior which is expected to overpower the metallic background at sufficiently low temperatures. We find empirically that the concept of a Fe...

Using ab initio electronic structure calculations employing the LDA+U method we have investigated the exchange coupling in materials containing Eu in Eu formal valency including: (i) insulating ferromagnets (EuO, EuS, EuSe, EuTe), and (ii) elemental metal BCC Eu. The total energies calculated with constrained magnetic structures were mapped on the Heisenberg Hamiltonian in order to investigate ...

Dissolved gas analysis (DGA) is attracting greater and greater interest from researchers as a fault diagnostic tool for power transformers filled with vegetable insulating oils. This paper presents experimental results of dissolved gases in insulating oils under typical electrical and thermal faults in transformers. The tests covered three types of insulating oils, including two types of vegeta...

the infrastructure of the electricity grid and super grid system in the hitherto industrialized world was to a large extent built up in the decades following world war ii with a peak in investments around 1960-1980. this means that the flotilla of power transformers is now starting to reach projected lifetime of around 40 years. during the last couple of decades there has also been an ongoing d...

This paper describes a simple and reliable method of improving the surface insulation strength of a spacer used in vacuum. The method is to roughen the spacer surface to an average roughness R higher than 1 or 2 m. The material of the spacer a examined is SiO , PMMA, PTFE or Al O and their shape is a right cylinder with 2 2 3 10 mm in height and 54 mm in diameter. The spacer is subjected to a r...

We report a metal to insulator transition (MIT) in disordered films of molecularly linked gold nanoparticles (NPs). As the number of carbons (n) of alkanedithiol linker molecules (C(n)S2) is varied, resistance (R) at low temperature (T = 2 K) and at 200 K, as well as trends in R vs T data at intermediate temperatures, all point to an MIT occurring at n = 5. We describe these results in a contex...