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Wenlin Feng - One of the best experts on this subject based on the ideXlab platform.
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investigations of the spin hamiltonian parameters and tetragonal distortions due to jahn teller Effect for the monovalent d9 ni pd pt impurity centers in agcl crystals
2010Co-Authors: Wenlin Feng, Weiqing Yang, Wenchenc Zheng, Xueming LiAbstract:Abstract When the monovalent m d 9 ions Ni + (3d 9 ), Pd + (4d 9 ) and Pt + (5d 9 ) substitute for the Ag + ions in AgCl crystal, the cubic chlorine octahedron surrounding Ag + in the host AgCl crystal distorts into the tetragonally elongated octahedron in the m d 9 impurity center owing to the Jahn–Teller Effect. The spin-Hamiltonian parameters ( g factors g || , g ⊥ and hyperfine structure constants A || , A ⊥ ) of the tetragonal m d 9 centers in AgCl are calculated from the high-order perturbation formulas based on the cluster approach, in which the admixture between d orbitals of d n ion and p orbitals of ligand ion via covalence Effect are taken into account. From the calculations, the spin-Hamiltonian parameters of these tetragonal m d 9 centers in AgCl are explained reasonably and the tetragonal distortions (characterized by the tetragonal elongation Δ R = R || − R ⊥ , where R || and R ⊥ denote the metal–ligand distances parallel with and perpendicular to the tetragonal axis) of these centers due to Jahn–Teller Effect are obtained. The results are discussed.
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investigations of the spin hamiltonian parameters and tetragonal distortion due to the jahn teller Effect for cu h2o 62 clusters in c nh2 3al so4 2 6h2o cu2 crystal
2010Co-Authors: Wenlin Feng, Wen-chen Zheng, Weiqing YangAbstract:Abstract When Cu2+ ion occupies the trigonal Al3+ (II) site in guanidinium aluminium sulphate hexahydrate (GASH) (C(NH2)3Al(SO4)2·6H2O) crystals, the trigonal Al(H2O)63+ octahedron in the host GASH crystal changes to the tetragonally-elongated Cu(H2O)62+ octahedron in the impurity center due to the Jahn–Teller Effect. The tetragonal distortion (characterized by ΔR=R∥–R⊥, where R∥ and R⊥ represent the metal–ligand distances parallel with and perpendicular to the C4 axis) of this Cu(H2O)62+ cluster is studied by calculating its spin-Hamiltonian parameters (g factors g∥, g⊥ and hyperfine structure constants A∥ and A⊥) from two theoretical methods, the complete diagonalization (of energy matrix) method (CDM) and the perturbation theory method (PTM). Both methods are based on the cluster approach in which the admixture between the d orbitals of 3dn ion and the p orbitals of ligand ion is considered. The calculated results show that both methods can be used to calculate the spin-Hamiltonian parameters and to determine the structure of 3d9 clusters in crystals. These results are discussed.
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spin hamiltonian parameters and tetragonal distortion due to the jahn teller Effect for cu2 centres in trigonal zn bro3 center dot 6h2o crystal
2009Co-Authors: Wenlin Feng, Lv He, Weiqing Yang, Wen-chen ZhengAbstract:The spin-Hamiltonian parameters (g factors g//, g perpendicular to and hyperfine structure constants 65A// and 65A perpendicular to) for the tetragonal Cu2+ centres in trigonal Zn(BrO3)center dot 6H2O crystal are calculated from the complete diagonalization (of energy matrix) method (CDM) based on the cluster approach. In the CDM, the Zeeman and hyperfine interaction terms are added to the Hamiltonian in the conventional CDM and the contributions to the spin-Hamiltonian parameters from both the spin-orbit coupling parameter of central d9 ion and that of ligand ion are included. The calculated spin-Hamiltonian parameters of Zn(BrO3)center dot 6H2O: Cu2+ show good agreement with the experimental values and the tetragonal elongation (characterized by R=R// - R perpendicular to, where R// and R perpendicular to represent the metal-ligand distances parallel with and perpendicular to the C4 axis) due to the static Jahn-Teller Effect is obtained from the calculations. The results are discussed.
Naoya Iwahara - One of the best experts on this subject based on the ideXlab platform.
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jahn teller Effect in the cubic fullerides a 3 c 60
2021Co-Authors: Zhishuo Huang, Tohru Sato, Naoya Iwahara, Munirah D Albaqami, Liviu F ChibotaruAbstract:Compared to isolated ${\mathrm{C}}_{60}^{3\ensuremath{-}}$ ions, characterized by a three-dimensional equipotential trough at the bottom of the lowest adiabatic potential energy surface (APES), the Jahn-Teller (JT) Effect in cubic fullerides is additionally influenced by the interaction of JT distortions at ${\mathrm{C}}_{60}$ sites with vibrational modes of the lattice. This leads to modification of JT stabilization energy and to the warping of the trough at each fullerene site, as well as to the interaction of JT distortions at different sites. Here we investigate these Effects in three fcc fullerides with $A=\mathrm{K}$, Rb, Cs and in ${\mathrm{Cs}}_{3}{\mathrm{C}}_{60}$ with bcc (A15) structure. DFT calculations of orbital vibronic coupling constants at ${\mathrm{C}}_{60}$ sites and of phonon spectra have been done for fully ordered lattices (1 ${\mathrm{C}}_{60}/\mathrm{u}.\mathrm{c}.$). Based on them the elastic response function for local JT distortions has been evaluated and the lowest APES investigated. To this end an expression for the latter as a function of trough coordinates of all sites has been derived. The results show that the JT stabilization energy slightly increases compared to an isolated ${\mathrm{C}}_{60}^{3\ensuremath{-}}$ and a warping of the trough of a few meV occurs. The interaction of JT distortions on nearest- and next-nearest-neighbor fullerene sites is of similar order of magnitude. These Effects arise first of all due to the interaction of ${\mathrm{C}}_{60}$ sites with the displacements of neighbor alkali atoms and are more pronounced in fcc fullerides than in the A15 compound. The results of this study support the picture of weakly hindered independent rotations of JT deformations at ${\mathrm{C}}_{60}$ sites in cubic ${A}_{3}{\mathrm{C}}_{60}$.
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dynamical jahn teller instability in metallic fullerides
2015Co-Authors: Naoya Iwahara, Liviu F ChibotaruAbstract:Dynamical Jahn-Teller Effect has escaped so far direct observation in metallic systems. It is particularly believed to be quenched also in correlated conductors with orbitally degenerate sites such as cubic fullerides. Here the Gutzwiller approach is extended to treat electron correlation over metals with Jahn-Teller active sites and applied to the investigation of the ground state of K$_3$C$_{60}$. It is shown that dynamical Jahn-Teller instability fully develops in this material when the interelectron repulsion $U$ on C$_{60}$ sites exceeds some critical value. The latter is found to be lower than the current estimates of $U$, meaning that dynamical Jahn-Teller Effect takes place in all cubic fullerides. This leads to strong splitting of LUMO orbitals on C$_{60}$ sites and calls for reconsideration of the role of orbital degeneracy in the Mott-Hubbard transition in fullerides.
Liviu F Chibotaru - One of the best experts on this subject based on the ideXlab platform.
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jahn teller Effect in the cubic fullerides a 3 c 60
2021Co-Authors: Zhishuo Huang, Tohru Sato, Naoya Iwahara, Munirah D Albaqami, Liviu F ChibotaruAbstract:Compared to isolated ${\mathrm{C}}_{60}^{3\ensuremath{-}}$ ions, characterized by a three-dimensional equipotential trough at the bottom of the lowest adiabatic potential energy surface (APES), the Jahn-Teller (JT) Effect in cubic fullerides is additionally influenced by the interaction of JT distortions at ${\mathrm{C}}_{60}$ sites with vibrational modes of the lattice. This leads to modification of JT stabilization energy and to the warping of the trough at each fullerene site, as well as to the interaction of JT distortions at different sites. Here we investigate these Effects in three fcc fullerides with $A=\mathrm{K}$, Rb, Cs and in ${\mathrm{Cs}}_{3}{\mathrm{C}}_{60}$ with bcc (A15) structure. DFT calculations of orbital vibronic coupling constants at ${\mathrm{C}}_{60}$ sites and of phonon spectra have been done for fully ordered lattices (1 ${\mathrm{C}}_{60}/\mathrm{u}.\mathrm{c}.$). Based on them the elastic response function for local JT distortions has been evaluated and the lowest APES investigated. To this end an expression for the latter as a function of trough coordinates of all sites has been derived. The results show that the JT stabilization energy slightly increases compared to an isolated ${\mathrm{C}}_{60}^{3\ensuremath{-}}$ and a warping of the trough of a few meV occurs. The interaction of JT distortions on nearest- and next-nearest-neighbor fullerene sites is of similar order of magnitude. These Effects arise first of all due to the interaction of ${\mathrm{C}}_{60}$ sites with the displacements of neighbor alkali atoms and are more pronounced in fcc fullerides than in the A15 compound. The results of this study support the picture of weakly hindered independent rotations of JT deformations at ${\mathrm{C}}_{60}$ sites in cubic ${A}_{3}{\mathrm{C}}_{60}$.
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dynamical jahn teller instability in metallic fullerides
2015Co-Authors: Naoya Iwahara, Liviu F ChibotaruAbstract:Dynamical Jahn-Teller Effect has escaped so far direct observation in metallic systems. It is particularly believed to be quenched also in correlated conductors with orbitally degenerate sites such as cubic fullerides. Here the Gutzwiller approach is extended to treat electron correlation over metals with Jahn-Teller active sites and applied to the investigation of the ground state of K$_3$C$_{60}$. It is shown that dynamical Jahn-Teller instability fully develops in this material when the interelectron repulsion $U$ on C$_{60}$ sites exceeds some critical value. The latter is found to be lower than the current estimates of $U$, meaning that dynamical Jahn-Teller Effect takes place in all cubic fullerides. This leads to strong splitting of LUMO orbitals on C$_{60}$ sites and calls for reconsideration of the role of orbital degeneracy in the Mott-Hubbard transition in fullerides.
Tohru Sato - One of the best experts on this subject based on the ideXlab platform.
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jahn teller Effect in the cubic fullerides a 3 c 60
2021Co-Authors: Zhishuo Huang, Tohru Sato, Naoya Iwahara, Munirah D Albaqami, Liviu F ChibotaruAbstract:Compared to isolated ${\mathrm{C}}_{60}^{3\ensuremath{-}}$ ions, characterized by a three-dimensional equipotential trough at the bottom of the lowest adiabatic potential energy surface (APES), the Jahn-Teller (JT) Effect in cubic fullerides is additionally influenced by the interaction of JT distortions at ${\mathrm{C}}_{60}$ sites with vibrational modes of the lattice. This leads to modification of JT stabilization energy and to the warping of the trough at each fullerene site, as well as to the interaction of JT distortions at different sites. Here we investigate these Effects in three fcc fullerides with $A=\mathrm{K}$, Rb, Cs and in ${\mathrm{Cs}}_{3}{\mathrm{C}}_{60}$ with bcc (A15) structure. DFT calculations of orbital vibronic coupling constants at ${\mathrm{C}}_{60}$ sites and of phonon spectra have been done for fully ordered lattices (1 ${\mathrm{C}}_{60}/\mathrm{u}.\mathrm{c}.$). Based on them the elastic response function for local JT distortions has been evaluated and the lowest APES investigated. To this end an expression for the latter as a function of trough coordinates of all sites has been derived. The results show that the JT stabilization energy slightly increases compared to an isolated ${\mathrm{C}}_{60}^{3\ensuremath{-}}$ and a warping of the trough of a few meV occurs. The interaction of JT distortions on nearest- and next-nearest-neighbor fullerene sites is of similar order of magnitude. These Effects arise first of all due to the interaction of ${\mathrm{C}}_{60}$ sites with the displacements of neighbor alkali atoms and are more pronounced in fcc fullerides than in the A15 compound. The results of this study support the picture of weakly hindered independent rotations of JT deformations at ${\mathrm{C}}_{60}$ sites in cubic ${A}_{3}{\mathrm{C}}_{60}$.
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jahn teller Effect in coronene monoanion a comparative study with corannulene monoanion
2003Co-Authors: Tohru Sato, Hideaki Tanaka, Atsushi Yamamoto, Yasutaka Kuzumoto, Ken TokunagaAbstract:Abstract We calculate the electronic and geometric structure of coronene monoanion, C 24 H 12 − , and observe the electron spin resonance (ESR) spectra of the monoanion in solution, to compare with the Jahn–Teller Effect in corannulene monoanion, C 20 H 10 − . The symmetries of the optimized structures are C 2 h and D 2 h for a minimum and a saddle point, respectively. The group-theoretical consideration shows that sixth anharmonic warping term can give rise to the energy minimum structure with C 2 h symmetry. Although the ESR spectra of doped corannulene monoanion have shown complicated hyperfine splittings due to the Jahn–Teller Effect, those of coronene monoanion exhibited equally spaced 13 peaks due to the equivalent 12 hydrogens and no hyperfine structure due to the Jahn–Teller Effect down to 200 K, which signifies that the energy barrier between the minima of coronene monoanion is lower than that of corannulene monoanion. The validity of the epikernel principle for the static Jahn–Teller distortion is also discussed.
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an esr study on jahn teller Effect in corannulene monoanion
2000Co-Authors: Tohru Sato, Atsushi Yamamoto, Hideaki TanakaAbstract:Abstract Solution ESR spectra of alkali-metal-doped corannulene monoanion, C 20 H 10 − , have been observed from RT to 183 K. Eleven peaks have been observed from RT to 273 K. As the decrease of temperature, the 11 signals due to ten equivalent protons split into complicated ones. This behavior has been interpreted in terms of pseudorotation about the C 5 v Jahn–Teller crossing. The potential barriers between five equivalent C s wells originating from the fifth-order anharmonic term have been estimated to be ca. 2.2×10 −3 eV.
H Iwasawa - One of the best experts on this subject based on the ideXlab platform.
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fermi surfaces and orbital polarization in superconducting ceo0 5 f0 5bis2 revealed by angle resolved photoemission spectroscopy
2015Co-Authors: T Sugimoto, D Ootsuki, Corentin Morice, Emilio Artacho, S S Saxena, Eike F Schwier, Mingtian Zheng, Yoshitsugu Kojima, H IwasawaAbstract:We have investigated the electronic structure of BiS$_2$-based CeO$_{0.5}$F$_{0.5}$BiS$_2$ superconductor using polarization-dependent angle-resolved photoemission spectroscopy (ARPES), and succeeded in elucidating the orbital characters on the Fermi surfaces. In the rectangular Fermi pockets around X point, the straight portion parallel to the $k_y$ direction is dominated by Bi $6p_x$ character. The orbital polarization indicates the underlying quasi-one-dimensional electronic structure of the BiS$_2$ system. Moreover, distortions on tetragonally aligned Bi could give rise to the band Jahn-Teller Effect.
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fermi surfaces and orbital polarization in superconducting ceo 0 5 f 0 5 bis 2 revealed by angle resolved photoemission spectroscopy
2015Co-Authors: T Sugimoto, D Ootsuki, Corentin Morice, Emilio Artacho, S S Saxena, Eike F Schwier, Mingtian Zheng, Yoshitsugu Kojima, H IwasawaAbstract:We have investigated the electronic structure of ${\mathrm{BiS}}_{2}$-based ${\mathrm{CeO}}_{0.5}{\mathrm{F}}_{0.5}{\mathrm{BiS}}_{2}$ superconductor using polarization-dependent angle-resolved photoemission spectroscopy (ARPES), and succeeded in elucidating the orbital characters on the Fermi surfaces. In the rectangular Fermi pockets around the $X$ point, the straight portion parallel to the ${k}_{y}$ direction is dominated by Bi $6{p}_{x}$ character. The orbital polarization indicates the underlying quasi-one-dimensional electronic structure of the ${\mathrm{BiS}}_{2}$ system. Moreover, distortions on tetragonally aligned Bi could give rise to the band Jahn-Teller Effect.
