The adsorption and dissociation of O2 molecules at the Be(0001) surface is studied by using density-functional theory within the generalized gradient approximation and a supercell approach. The physisorbed and chemiso...
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The adsorption and dissociation of O2 molecules at the Be(0001) surface is studied by using density-functional theory within the generalized gradient approximation and a supercell approach. The physisorbed and chemisorbed molecular precursor states are identified to be along the parallel and vertical channels, respectively. It is shown that the vertical channel with O2 being at the hcp hollow sites of the Be(0001) surface is the most stable channel for the molecular chemisorption. The electronic and magnetic properties of this most stable chemisorbed molecular state are studied, which show that the electrons transfer forth and back between the spin-resolved antibonding π∗ molecular orbitals and surface Be sp states. A distinct covalent weight in the molecule-metal bond is also shown. The dissociation of O2 is determined by calculating the adiabatic potential energy surfaces, wherein the T-Y channel is found to be the most stable and favorable for dissociative adsorption of O2. Remarkably, we predict that unlike other simple sp metal surfaces such as Al(111) and Mg(0001), the adiabatic dissociation process of O2 at Be(0001) is an activated type with a sizeable energy barrier.
作者：
Adam B. HopkinsFrank H. StillingerSalvatore TorquatoDepartment of Chemistry
Princeton Institute for the Science and Technology of Materials Program in Applied and Computational Mathematics Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA and School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08544 USA
Elementary smooth functions (beyond contact) are employed to construct pair correlation functions that mimic jammed disordered sphere packings. Using the g2-invariant optimization method of Torquato and Stillinger [J....
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Elementary smooth functions (beyond contact) are employed to construct pair correlation functions that mimic jammed disordered sphere packings. Using the g2-invariant optimization method of Torquato and Stillinger [J. Phys. Chem. B 106, 8354 (2002)], parameters in these functions are optimized under necessary realizability conditions to maximize the packing fraction ϕ and average number of contacts per sphere Z. A pair correlation function that incorporates the salient features of a disordered packing and that is smooth beyond contact is shown to permit a ϕ of 0.6850: this value represents a 45% reduction in the difference between the maximum for congruent hard spheres in three dimensions, π/18≈0.7405 and 0.64, the approximate fraction associated with maximally random jammed packings in three dimensions. We show that, surprisingly, the continued addition of elementary functions consisting of smooth sinusoids decaying as r−4 permits packing fractions approaching π/18. A translational order metric is used to discriminate between degrees of order in the packings presented. We find that to achieve higher packing fractions, the degree of order must increase, which is consistent with the results of a previous study [Torquato et al., Phys. Rev. Lett. 84, 2064 (2000)].
Spiral waves and spatiotemporal chaos are sometimes harmful and should be controlled. In this paper spiral waves and spatiotemporal chaos are successfully eliminated by the pulse with a very specific spatiotemporal co...
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Spiral waves and spatiotemporal chaos are sometimes harmful and should be controlled. In this paper spiral waves and spatiotemporal chaos are successfully eliminated by the pulse with a very specific spatiotemporal configuration. The excited position D of spiral waves or spatiotemporal chaos is first recorded at an arbitrary time （to）. When the system at the domain D enters a recovering state, the external pulse is injected into the domain. If the intensity and the working time of the pulse are appropriate, spiral waves and spatiotemporal chaos can finally be eliminated because counter-directional waves can be generated by the pulse. There are two advantages in the method. One is that the tip can be quickly eliminated together with the body of spiral wave, and the other is that the injected pulse may be weak and the duration can be very short so that the original system is nearly not affected, which is important for practical applications.
We stretched a DNA molecule using an atomic force microscope (AFM) and quantified the mechanical properties associated with B and S forms of double-stranded DNA (dsDNA), molten DNA, and single-stranded DNA. We also fi...
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Charge transfer due to collisions of ground-state O3+(2s22p P2) ions with He is investigated using the quantum-mechanical molecular-orbital close-coupling (QMOCC) method. The ab initio adiabatic potentials and radial ...
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Charge transfer due to collisions of ground-state O3+(2s22p P2) ions with He is investigated using the quantum-mechanical molecular-orbital close-coupling (QMOCC) method. The ab initio adiabatic potentials and radial couplings utilized in the QMOCC calculations are obtained from the multireference single- and double-excitation configuration interaction approach. State-selective and total charge-transfer cross sections are calculated for collision energies from 0.01 eV/u to 1 keV/u. Comparison with existing data reveals that the present QMOCC calculations are in good harmony with the measured total single-electron charge-transfer cross sections. Excellent agreement with the available experimental data is also found for state-selective cross sections at the measured energy region.
The electron and hole states and confining potential for cylindrical core-shell structure with type-II band alignment are obtained from a numerical solution of the self-consistent Schrödinger-Poisson system of eq...
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The electron and hole states and confining potential for cylindrical core-shell structure with type-II band alignment are obtained from a numerical solution of the self-consistent Schrödinger-Poisson system of equations. The photoluminescence (PL) kinetics is theoretically analyzed, with the nanostructure size dispersion taken into account. The results are applied to the radiative recombination in the system of ZnTe/ZnSe stacked quantum dots. A good agreement with both cw and time-resolved experimental observations is found. It is shown that size distribution results in the PL decay that has essentially nonexponential behavior even at the tail of the decay where the carrier lifetime is almost the same due to slowly changing overlap of the electron and hole wave functions. Finally, a model situation applicable to colloidal core-shell nanowires is investigated and discussed.
We investigate the dissociation of O2 on Pb(111) surface using first-principles calculations. It is found that in a practical high-vacuum environment, the adsorption of molecular O2 takes place on clean Pb surfaces on...
We investigate the dissociation of O2 on Pb(111) surface using first-principles calculations. It is found that in a practical high-vacuum environment, the adsorption of molecular O2 takes place on clean Pb surfaces only at low temperatures such as 100 K, but the O2 easily desorbs at (elevated) room temperatures. It is further found that the Pb adatoms enhance the molecular adsorption and activate the adsorbed O2 to dissociate during subsequent room-temperature annealing. Our theory explains the observation of a two-step oxidation process on the Pb surfaces by the unique role of Pb adatoms.
In recent years, a series of opacity diagnostics have been developed at the Research Center of Laser Fusion in China. Two types of cavities (a conical cavity called a type I target, and a cylindrical cavity with foam ...
This paper investigates the interaction of a small number of modes in the two-fluid Kelvin-Helmholtz instability at the nonlinear regime by using a two-dimensional hydrodynamic code. This interaction is found to be re...
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This paper investigates the interaction of a small number of modes in the two-fluid Kelvin-Helmholtz instability at the nonlinear regime by using a two-dimensional hydrodynamic code. This interaction is found to be relatively long range in wave-number space and also it acts in both directions, i.e. short wavelengths affect long wavelengths and vice versa. There is no simple equivalent transformation from a band of similar modes to one mode representing their effective amplitude. Three distinct stages of interaction have been identified.
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