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Huang L.,CAS Institute of Physics | Huang L.,Science and Technology on Surface Physics and Chemistry Laboratory | Wang Y.,CAS Institute of Physics | Dai X.,CAS Institute of Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The metal-insulator and spin state transitions of CoO under high pressure are studied by using density functional theory combined with dynamical mean-field theory. Our calculations predict that the metal-insulator transition in CoO is a typical orbital selective insulator-to-metal transition, where the t 2g orbitals of a Co 3d shell become metallic first around 60 GPa while the e g orbitals still remain insulating until 170 GPa. Further studies of the spin states of a Co 3d shell reveal that the orbital selective Mott phase in the intermediate pressure regime is mainly stabilized by the high-spin state of the Co 3d shell, and the transition from this phase to the fully metallic state is driven mainly by the high-spin to low-spin transition of the Co2 + ions. Our results are in good agreement with the most recent transport and x-ray emission experiments under high pressure. © 2012 American Physical Society. Source


Huang L.,CAS Institute of Physics | Huang L.,Science and Technology on Surface Physics and Chemistry Laboratory | Du L.,CAS Institute of Physics | Dai X.,CAS Institute of Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Motivated by the unexplored complexity of the phase diagrams for multiorbital Hubbard models, a three-band Hubbard model at integer fillings (N=4) with orbital degeneracy lifted partially by crystal field splitting is analyzed systematically in this work. By using the single-site dynamical mean-field theory and rotationally invariant Gutzwiller approximation, we have computed the full phase diagram with Coulomb interaction strength U and crystal field splitting Δ. We find a large region in the phase diagram where an orbital-selective Mott phase will be stabilized by the positive crystal field lifting the orbital degeneracy. Further analysis indicates that Hund's rule coupling is essential for the orbital-selective Mott phase, and the transition toward this phase is accompanied by a high-spin to low-spin transition. Such a model may be relevant for the recently discovered Ru-based materials. © 2012 American Physical Society. Source


Zhu X.-G.,University of Aarhus | Zhu X.-G.,Science and Technology on Surface Physics and Chemistry Laboratory | Hofmann P.,University of Aarhus
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

Topological insulators support metallic surface states whose existence is protected by the bulk band structure. It was predicted early that the topology of the surface-state Fermi contour should depend on several factors, such as the surface orientation and termination, and this raises the question to what degree a given surface state is protected by the bulk electronic structure upon structural changes. Using tight-binding calculations, we explore this question for the prototypical topological insulator Bi1-xSbx, studying different terminations of the (111) and (110) surfaces. We also consider the implications of the topological protection for (110) surfaces for the semimetals Bi and Sb. © 2014 American Physical Society. Source


Zhao P.,University of Bordeaux 1 | Zhao P.,Science and Technology on Surface Physics and Chemistry Laboratory | Li N.,University of Bordeaux 1 | Salmon L.,French National Center for Scientific Research | And 3 more authors.
Chemical Communications | Year: 2013

"Click" chemistry now offers access to a great variety of triazoles, and the first example of a strategy to stabilize gold nanoparticles (AuNPs) with a new 1,2,3-triazole-mPEG ligand is developed here together with preliminary examples of possible applications. © 2013 The Royal Society of Chemistry. Source


Lu H.Y.,Science and Technology on Surface Physics and Chemistry Laboratory
Materials Science Forum | Year: 2015

In this paper, we study the ground-state and lattice dynamical properties of β-UH--3 by means of the first-principles density functional theory within the local spin-density approximation (LSDA)+U formulism. The lattice constants and electronic structure are correctly described by taking into account the strong on-site Coulomb repulsion among the 5f electrons localized on uranium atoms. Good agreement with experiments is achieved by tuning the effective Hubbard parameter at around 4 eV. The phonon band structure confirms the dynamical stability of β-UH--3, and the Raman-active modes are consistent with Raman spectrum measurements. The substitution of the deuterium (tritium) atom for hydrogen atom makes significant variations in the typical frequency of Raman-active modes. It is found that the Raman-active mode frequency is approximately inversely proportional to the square root of the hydrogen isotope mass. We conclude that Raman spectrum provides a powerful method for detecting hydrogen isotopic effects. © (2015) Trans Tech Publications, Switzerland. Source

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