Electronic Structure Of The Hydride Pd3feh

A self-consistent calculation of the electronic structure of Pd3FeH is presented, using the linear combination of muffin-tin orbitals method. We first briefly discuss the paramagnetic phase of the hydride. We then proceed to the discussion of the ferromagnetic phase of Pd3FeH. The analysis of the energy bands and densities of states gives a good understanding of the influence of hydrogen in this compound. We show any hydrogen uptake drastically decreases the magnetic moments of Pd3Fe. We also find a marked increase in the linear coefficient of specific heat, showing great alterations in the physical properties of Pd3Fe upon hydrogenation. © 1987 The American Physical Society.36145245

Magnetic Properties And Calculated Electronic Structure Of Iron-palladium Alloys

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The electronic structure of iron-palladium alloys are studied using the self-consistent linear muffin-tin orbital (LMTO) method. In particular, three compounds are analyzed, namely, Pd3Fe, PdFe, and PdFe3 and their stability investigated with respect to the iron concentration. Results are obtained from ferromagnetic calculations for each alloy. Our discussion on internal excess energy shows the PdFe3 ordered structure to be at best metastable with respect to its disordered alloy, while Pd3Fe and PdFe are stable compounds. Results for PdFe3 show a collapse of its magnetic moment as a function of the lattice parameter. © 1992 The American Physical Society.461489158925 2010/00863-0; FAPESP; São Paulo Research Foundation; 2011/09240-9; FAPESP; São Paulo Research Foundation; 2012/21198-0; FAPESP; São Paulo Research FoundationFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Quasienergy Spectra Of Quantum Dynamical Systems

We present a technique that yields in analytic fashion the quasienergy spectrum of bounded quantum systems in the presence of time-periodic perturbations. It also allows for the calculation of statistical averages using simple algebraic manipulations and provides tractable solutions even for systems with a large number of levels. We also report on numerical calculations for systems with few number of levels in and out of resonance, and which show the recurrences predicted by the Hogg-Huberman theorem [Phys. Rev. Lett. 48, 711 (1982); Phys. Rev. A 28, 22 (1983)]. © 1984 The American Physical Society.30417521759CONACYT; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; NCN; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; NRF; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; NSFC; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; DNRF; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; ERC; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; INFN; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; NKTH; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; NWO; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; OTKA; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; RAS; Nederlandse Organisatie voor Wetenschappelijk Onderzoek; RFBR; Nederlandse Organisatie voor Wetenschappelijk Onderzoek;  Nederlandse Organisatie voor Wetenschappelijk Onderzoek; STFC; Nederlandse Organisatie voor Wetenschappelijk Onderzoe

Unveiling the origin of oxygen atomic impurities in Au nanowires

The appearance of unusually large Au-Au bond distances in linear atomic chains (LACs) of Au nanowires is commonly attributed to the presence of atomic impurities. However, the origin of those contaminants is unknown. We present a study based on density functional theory calculations using quasistatic (T=0) and finite-temperature ab initio molecular-dynamics simulations of a possible route for the formation of atomic impurities in Au nanowires. This process starts with the adsorption of an O2 molecule followed by a CO molecule on Au LACs, leading to the formation of an intermediate O2CO complex. Upon thermal activation at finite temperatures, the complex is able to proceed to oxidation forming a CO2 molecule and leaving an atomic O impurity in the Au LAC

Gold nanowires and the effect of impurities

Metal nanowires and in particular gold nanowires have received a great deal of attention in the past few years. Experiments on gold nanowires have prompted theory and simulation to help answer questions posed by these studies. Here we present results of computer simulations for the formation, evolution and breaking of very thin Au nanowires. We also discuss the influence of contaminants, such as atoms and small molecules, and their effect on the structural and mechanical properties of these nanowires

The role of structural evolution on the quantum conductance behavior of gold nanowires during stretching

Gold nanowires generated by mechanical stretching have been shown to adopt only three kinds of configurations where their atomic arrangements adjust such that either the [100], [111] or [110] zone axes lie parallel to the elongation direction. We have analyzed the relationship between structural rearrangements and electronic transport behavior during the elongation of Au nanowires for each of the three possibilities. We have used two independent experiments to tackle this problem, high resolution transmission high resolution electron microscopy to observe the atomic structure and a mechanically controlled break junction to measure the transport properties. We have estimated the conductance of nanowires using a theoretical method based on the extended H\"uckel theory that takes into account the atom species and their positions. Aided by these calculations, we have consistently connected both sets of experimental results and modeled the evolution process of gold nanowires whose conductance lies within the first and third conductance quanta. We have also presented evidence that carbon acts as a contaminant, lowering the conductance of one-atom-thick wires.Comment: 10 page

Calibration of the length of a chain of single gold atoms

Using a scanning tunneling microscope or mechanically controllable break junctions it has been shown that it is possible to control the formation of a wire made of single gold atoms. In these experiments an interatomic distance between atoms in the chain of ~3.6 Angstrom was reported which is not consistent with recent theoretical calculations. Here, using precise calibration procedures for both techniques, we measure length of the atomic chains. Based on the distance between the peaks observed in the chain length histogram we find the mean value of the inter-atomic distance before chain rupture to be 2.6 +/- 0.2 A . This value agrees with the theoretical calculations for the bond length. The discrepancy with the previous experimental measurements was due to the presence of He gas, that was used to promote the thermal contact, and which affects the value of the work function that is commonly used to calibrate distances in scanning tunnelling microscopy and mechanically controllable break junctions at low temperatures.Comment: 6 pages, 6 figure

Towards unified understanding of conductance of stretched monatomic contacts

When monatomic contacts are stretched, their conductance behaves in qualitatively different ways depending on their constituent atomic elements. Under a single assumption of resonance formation, we show that various conductance behavior can be understood in a unified way in terms of the response of the resonance to stretching. This analysis clarifies the crucial roles played by the number of valence electrons, charge neutrality, and orbital shapes.Comment: 2 figure

Resposta da soja à adubação com zinco em solo com teores acima do nível crítico

O objetivo deste trabalho foi avaliar a resposta da soja a estratégias de adubação com zinco, em Latossolo com disponibilidade inicial do micronutriente acima do nível crítico. O experimento consistiu em 16 tratamentos com diferentes combinações de fontes, doses e formas de aplicação de Zn. Foram avaliados a produtividade da soja e os teores de Zn no solo, nas folhas e nos grãos. A fertilização com Zn aumentou a produtividade da soja, mesmo em solo com teor do micronutriente acima do nível crítico. A resposta à adubação varia de acordo com as estratégias de aplicação de zinco. Há indícios de que o nível crítico de Zn no solo deve ser revisto