20,068 research outputs found

    The properties of kaonic nuclei in relativistic mean-field theory

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    The static properties of some possible light and moderate kaonic nuclei, from C to Ti, are studied in the relativistic mean-field theory. The 1s and 1p state binding energies of KK^- are in the range of 739673\sim 96 MeV and 226322\sim 63 MeV, respectively. The binding energies of 1p states increase monotonically with the nucleon number A. The upper limit of the widths are about 42±1442\pm 14 MeV for the 1s states, and about 71±1071\pm 10 MeV for the 1p states. The lower limit of the widths are about 12±412\pm 4 MeV for the 1s states, and 21±321\pm 3 MeV for the 1p states. If V030V_{0}\leq 30 MeV, the discrete KK^- bound states should be identified in experiment. The shrinkage effect is found in the possible kaonic nuclei. The interior nuclear density increases obviously, the densest center density is about 2.1ρ02.1\rho_{0}.Comment: 9 pages, 2 tables and 1 figure, widths are considered, changes a lo

    First-principles study of native point defects in Bi2Se3

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    Using first-principles method within the framework of the density functional theory, we study the influence of native point defect on the structural and electronic properties of Bi2_2Se3_3. Se vacancy in Bi2_2Se3_3 is a double donor, and Bi vacancy is a triple acceptor. Se antisite (SeBi_{Bi}) is always an active donor in the system because its donor level (ε\varepsilon(+1/0)) enters into the conduction band. Interestingly, Bi antisite(BiSe1_{Se1}) in Bi2_2Se3_3 is an amphoteric dopant, acting as a donor when μ\mue_e<<0.119eV (the material is typical p-type) and as an acceptor when μ\mue_e>>0.251eV (the material is typical n-type). The formation energies under different growth environments (such as Bi-rich or Se-rich) indicate that under Se-rich condition, SeBi_{Bi} is the most stable native defect independent of electron chemical potential μ\mue_e. Under Bi-rich condition, Se vacancy is the most stable native defect except for under the growth window as μ\mue_e>>0.262eV (the material is typical n-type) and Δ\Deltaμ\muSe_{Se}<<-0.459eV(Bi-rich), under such growth windows one negative charged BiSe1_{Se1} is the most stable one.Comment: 7 pages, 4 figure
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