Symmetry Violations in Partially Oxidized One-Dimensional (1D)Transition Metal Polymers. Metal-Ligand-Metal(M-L-M) Bridged Systems

1984 ◽  
Vol 39 (9) ◽  
pp. 807-829
Author(s):  
Michael C. Böhm
Keyword(s):  
Transition Metal ◽  
Density Wave ◽  
Tight Binding ◽  
Mean Field ◽  
Valence Bond ◽  
Hole State ◽  
One Dimensional ◽  
Metal Derivatives ◽  
A Charge ◽  
Metal Ligand

The band structure of the metal-ligand-metal (M-L-M) bridged quasi one-dimensional (1D) cyclopentadienylmanganese polymer, MnCp 1, has been studied in the unoxidized state and in a partly oxidized modification with one electron removed from each second MnCp fragment. The tight-binding approach is based on a semiempirical self-consistent-field (SCF) Hartree-Fock (HF) crystal orbital (CO) model of the INDO-type (intermediate neglect of differential overlap) combined with a statistical averaging procedure which has its origin in the grand canonical ensemble. The latter approximation allows for an efficient investigation of violations of the translation symmetries in the oxidized 1D material. The oxidation process in 1 is both ligand- and metal-centered (Mn 3d-2 states). The mean-field minimum corresponds to a charge density wave (CDW) solution with inequivalent Mn sites within the employed repeat-units. The symmetry adapted solution with electronically identical 3d centers is a maximum in the variational space. The coupling of this electronic instability to geometrical deformations is also analyzed. The ligand amplitudes encountered in the hole-state wave function prevent extremely large charge separations between the 3d centers which are found in ID systems without bridging moieties (e.g. Ni(CN)2-5 chain). The symmetry reduction in oxidized 1 is compared with violations of spatial symmetries in finite transition metal derivatives and simple solids. The stabilization of the valence bond-type (VB) solution is physically rationalized (i.e. left-right correlations between the 3d centers). The computational results derived for 1 are generalized to oxidized transition metal chains with band occupancies that are simple fractions of the number of stacking units and to 1D systems that deviate from this relation. The entropy-influence for temperatures T ≠ 0 is shortly discussed (stabilization of domain or cluster structures).

FRÖHLICH'S ONE-DIMENSIONAL SUPERCONDUCTOR WITH PARA-FERMI STATISTICS

1994 ◽  
Vol 08 (19) ◽  
pp. 1195-1200 ◽  
Author(s):  
V. L. SAFONOV ◽  
A. V. ROZHKOV
Keyword(s):  
Density Wave ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Wave State ◽  
One Dimensional ◽  
Fermi Statistics ◽  
The Mean ◽  
A Charge ◽  
Dimensional Crystal

The hypothesis that conduction electrons in a one-dimensional crystal obey para-Fermi statistics is discussed. Thermal properties of Fröhlich's model in the mean-field approximation are calculated within the framework of this hypothesis. It is shown that the temperature of the phase transition to a charge density wave state is greater in a system with parastatistics.

CHARGE DENSITY WAVE TRANSITIONS IN TWO-DIMENSIONAL TRANSITION METAL BRONZES AND OXIDES

1993 ◽  
Vol 07 (23n24) ◽  
pp. 3973-4003 ◽  
Author(s):  
P. FOURY ◽  
J.P. POUGET
Keyword(s):  
Transition Metal ◽  
Charge Density ◽  
Ground State ◽  
Charge Density Wave ◽  
Density Wave ◽  
Electron Localization ◽  
Two Dimensional ◽  
Fermi Surfaces ◽  
A Charge ◽  
Structural Instabilities

The structural instabilities towards the formation of a charge density wave (CDW) ground state exhibited by several layered Mo and W bronzes and oxides are reviewed. It is shown that in these two-dimensional (2D) metals, including the purple bronzes A x Mo 6 O 17 (A=K, Na, Tl; x≈1), the γ and η phases of MO 4 O 11 and the monophosphate tungsten bronzes with pentagonal tunnels ( PO 2)4 ( WO 3)2m(m=4, 6, 7), the CDW instability can be associated with particular chains of MoO 6 or WO 6 octahedra of the ReO 3 type slabs along which there is a strong overlap of the t 2g orbitals. The CDW critical wave vectors of the purple bronzes, Mo 4 O 11 and the tungsten bronzes with m=4 and 6 lead to a common nesting between differently oriented 1D Fermi surfaces. It is suggested that the anharmonic CDW modulation, which occurs in the tungsten bronzes with m≥7, could be the structural fingerprint of electron localization effects.

CHARGE-FLUX DENSITY WAVES: ANYONS IN A PERIODIC POTENTIAL

1991 ◽  
Vol 05 (21) ◽  
pp. 1431-1438
Author(s):  
D. M. Gaitonde ◽  
Sumathi Rao
Keyword(s):  
Flux Density ◽  
Periodic Potential ◽  
Mean Field Theory ◽  
Density Wave ◽  
Mean Field ◽  
Landau Levels ◽  
Filling Fraction ◽  
Lattice Periodicity ◽  
Magnetic Length ◽  
A Charge

We show that the lattice periodicity which causes a modulation of the charge density by a wave vector q also leads to a modulation of the flux density if the charged particles are anyons. Within mean field theory, we obtain a charge and flux density wave (CFDW) where the degenerate Landau levels of a constant magnetic field split into bands. For a weak periodic flux superimposed on a strong constant flux, anyon superconductivity at integer filling of Landau levels (corresponding to a statistics parameter of θ = π(1 − 1/ν) with ν = n = integer ) is not affected. However, at statistics corresponding to non-integer filling of Landau levels, for certain commensurability conditions between the lattice length (a), the magnetic length (l) and the filling fraction (ν), gaps open up at the Fermi level and convert an anyon metal into an anyon insulator.

X-ray diffuse scattering as precursor of incommensurate Peierls transitions in one-dimensional organic charge transfer conductors

2004 ◽  
Vol 219 (11) ◽  
Author(s):  
Jean-Paul Pouget
Keyword(s):  
Charge Transfer ◽  
Charge Density Wave ◽  
Diffuse Scattering ◽  
Lattice Distortion ◽  
Density Wave ◽  
Periodic Lattice ◽  
One Dimensional ◽  
X Ray ◽  
Charge Transfer Salts ◽  
A Charge

AbstractQuasi-one dimensional (1D) conductors of the TTF-TCNQ family of charge transfer salts exhibit a Peierls transition which stabilizes a periodic lattice distortion (PLD), accompanied by a charge density wave (CDW) modulation, with an incommensurate 2

Peculiarities of carrier scattering at the boundary of a normal metal and a quasi-one-dimensional conductor with a charge-density wave

JETP Letters ◽  
1996 ◽  
Vol 64 (4) ◽  
pp. 285-291 ◽  
Author(s):  
A. A. Sinchenko ◽  
Yu. I. Latyshev ◽  
S. G. Zybtsev ◽  
I. G. Gorlova ◽  
P. Monceau
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Normal Metal ◽  
One Dimensional ◽  
Carrier Scattering ◽  
A Charge

Observation of discommensuration arrays in transition metal substituted TaTe4

1990 ◽  
Vol 48 (4) ◽  
pp. 170-171
Author(s):  
J.C. Bennett ◽  
F.W. Boswell ◽  
J.M. Corbett ◽  
A. Prodan ◽  
S. Kohara
Keyword(s):  
Electron Diffraction ◽  
Transition Metal ◽  
Charge Density Wave ◽  
Room Temperature ◽  
Density Wave ◽  
Threshold Concentration ◽  
Transition Metal Doping ◽  
One Dimensional ◽  
Diffraction Patterns ◽  
Dimensional Crystal

TaTe4 is a quasi-one-dimensional crystal in which chains of Ta atoms along the c-axis are centered within extended cages of Te atoms in square antiprismatic coordination. The subcell structure is tetragonal with axes (axaxc). At room temperature, the crystal is modulated by a commensurate charge-density wave (CDW) which gives rise to a supercell with axes (2ax2ax3c). Transition metal doping of TaTe4 causes the modulation to become incommensurate.A series of mixed crystals (Ta1−xMx)Te with M = Nb, Ti or Zr have been examined using electron diffraction and electron microscopy. In each case, the modulation periodicity (as measured from the positions of the satellites in electron diffraction patterns) remains commensurate until a threshold concentration ( x ∼ .3 for Nb, ∼ .1 for Ti and Zr) is reached and then jumps discontinuously to an incommensurate value. Upon further substitution by Nb, the modulation periodicity varies with x, approaching that of NbTe as x approaches 1.0.

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