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We present a theoretical study of solid CO2 up to 50 GPa and 1500 K using first-principles calculations. In this pressure-temperature range, interpretations of recent experiments have suggested the existence of CO2 phases which are intermediate between molecular and covalent-bonded solids. We reexamine the concept of intermediate phases in the CO2 phase(More)
  • Fernando Miguel Pais, Graça Lobo, +39 authors Donna Eiskamp
  • 2000
Dissertação apresentada para obtenção do Grau de Doutor em Engenharia do Ambiente, ABSTRACT Genetic algorithms (GAs) have been used to solve difficult optimization problems in a number of fields. One of the advantages of these algorithms is that they operate well even in domains where little is known, thus giving the GA the flavor of a general purpose(More)
It is generally assumed that solid hydrogen will transform into a metallic alkali-like crystal at sufficiently high pressure. However, some theoretical models have also suggested that compressed hydrogen may form an unusual two-component (protons and electrons) metallic fluid at low temperature, or possibly even a zero-temperature liquid ground state. The(More)
The T2K experiment observes indications of ν(μ) → ν(e) appearance in data accumulated with 1.43×10(20) protons on target. Six events pass all selection criteria at the far detector. In a three-flavor neutrino oscillation scenario with |Δm(23)(2)| = 2.4×10(-3)  eV(2), sin(2)2θ(23) = 1 and sin(2)2θ(13) = 0, the expected number of such events is 1.5±0.3(syst).(More)
We have computed the melting line of lithium hydride up to 200 GPa using the two-phase simulation technique coupled with first-principles molecular dynamics. Our predicted melting temperature at high pressures varies slowly with compression, ranging from 2000 to 2450 K at 50-200 GPa pressures. The compressed fluid close to the melting line retains the ionic(More)
All elements, except for helium, appear to solidify into crystalline forms at zero temperature, and it is generally assumed that the introduction of lattice defects results in an increase in internal energy. beta-Rhombohedral boron, a thermodynamically stable form of elemental boron at high temperature, is known to have a large amount of partial occupied(More)
X-ray absorption spectroscopy and ab initio modeling of the experimental spectra have been used to investigate the effects of surface passivation on the unoccupied electronic states of CdSe quantum dots (QDs). Significant differences are observed in the unoccupied electronic structure of the CdSe QDs, which are shown to arise from variations in specific(More)
A viable Li/O 2 battery will require the development of stable electrolytes that do not continuously decompose during cell operation. Recent experiments suggest that reactions occurring at the interface between the liquid electrolyte and the solid lithium peroxide (Li 2 O 2) discharge phase are a major contributor to these instabilities. To clarify the(More)
We investigate the structure, topology, and dynamics of liquid water at the interface with natively hydroxylated (001) surfaces of InP and GaP photoelectrodes. Using ab initio molecular dynamics simulations, we show that contact with the semiconductor surface enhances the water hydrogen-bond strength at the interface. This leads to the formation of an(More)