309,864 research outputs found
Destruction of invariant circles for Gevrey area-preserving twist maps
In this paper, we show that for exact area-preserving twist maps on annulus,
the invariant circles with a given rotation number can be destroyed by
arbitrarily small Gevrey- perturbations of the integrable generating
function in the topology with .Comment: to appear in Journal of Dynamics and Differential Equations (JDDE).
arXiv admin note: text overlap with arXiv:1208.2840, arXiv:1106.613
Intrinsic Defects and Electronic Conductivity of TaON: First-Principles Insights
As a compound in between the tantalum oxide and nitride, the tantalum
oxynitride TaON is expected to combine their advantages and act as an efficient
visible-light-driven photocatalyst. In this letter, using hybrid functional
calculations we show that TaON has different defect properties from the binary
tantalum oxide and nitride: (i) instead of O or N vacancies or Ta
interstitials, the antisite is the dominant defect, which determines its
intrinsic n-type conductivity and the p-type doping difficulty; (ii) the
antisite has a shallower donor level than O or N vacancies, with a delocalized
distribution composed mainly of the Ta orbitals, which gives rise to
better electronic conductivity in the oxynitride than in the oxide and nitride.
The phase stability analysis reveals that the easy oxidation of TaON is
inevitable under O rich conditions, and a relatively O poor condition is
required to synthesize stoichiometric TaON samples
Thermodynamic Oxidation and Reduction Potentials of Photocatalytic Semiconductors in Aqueous Solution
We introduce an approach to calculate the thermodynamic oxidation and
reduction potentials of semiconductors in aqueous solution. By combining a
newly-developed ab initio calculation for compound formation energy and band
alignment with electrochemistry experimental data, this approach can be used to
predict the stability of almost any compound semiconductor in aqueous solution.
30 photocatalytic semiconductors have been studied, and a graph (a simplified
Pourbaix diagram) showing their valence/conduction band levels and
oxidation/reduction potentials is produced. Based on this graph, we have
studied the stabilities and trends against the oxidative and reductive
photocorrosion for compound semiconductors. We found that, only metal oxides
can be thermodynamically stable when used as the n-type photoanodes. All the
non-oxides are unstable due to easy oxidation by the photogenerated holes, but
they can be resistant to the reduction by electrons, thus stable as the p-type
photocathodes
Quantum Transport Calculations Using Periodic Boundary Conditions
An efficient new method is presented to calculate the quantum transports
using periodic boundary conditions. This method allows the use of conventional
ground state ab initio programs without big changes. The computational effort
is only a few times of a normal ground state calculation, thus it makes
accurate quantum transport calculations for large systems possible.Comment: 9 pages, 6 figure
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