Anisotropic metallic conductivity

The salt may be best described as a mixed-valence compound containing platinum in the 2.3+ oxidation state. The combination of the mixed-valence state, the very short Pt— Pt separation of 2.89 A (only approximately 0.1 A longer than in platinum metal), and the formation of linear Pt—Pt chains along the c axis gives rise to the high, anisotropic metallic conductivity in this material.1... 

In oriented metallic conducting polymers, with large anisotropy in conductivity, the anisotropic diffusion coefficient factor should be taken into account in the above model. The robustness of this metallic state can be verified from the field dependence of conductivity at low temperatures. For example, in the case of sample E with oj 2 200 S/cm (see Fig. 3.4), which is just on the metallic side of the M-I transition, a field of 8 T can induce a transition to the insulating state, as shown in Fig. 3.7. The corresponding W vs. T plot (Fig. 3.7a) is consistent with the fact that the system has moved from the metallic to the critical/insulating side. This is a typical example... 

The details of the EPR investigation of the graphite compound MCl6BF4M merit some discussion. Because the material is an electronic conductor, we suspended the polycrystalline sample in eicosane, melted the mixture under hot water, vibrated the sample to get random orientation, and froze the mixture under cold water. Because "CifcBF is an anisotropic conductor (it does not have metallic conductivity orthogonal to the planes), the interpretation of the EPR results requires care. Thus, in a thick plate of an isotropic metal as lithium, one observes a Dysonian asymmetry parameter A/B which is dependent on temperature, varying between... 

High electrical conductivity of organic conductors manifests itself in the IR spectra as anisotropic metal-like reflectivity associated with intermo-lecular charge transfer. Although an electron gas giving the plasma edge... 

One of the surprising results of the early pressure studies is shown in Fig. 10 [27]. In the range investigated, both transverse components of the conductivity increased with pressure at the same rate as important factors in the development of Weger s theory of the transverse conductivity of anisotropic metals [75]. In this... 

Graphite intercalation compounds have received widespread interest for two main reasons. First, intercalation results in compounds that have metallic conductivity. The electrical conductivity can approach that of copper metal and is highly anisotropic ratios of the conductivity in-plane to that along the c axis can be six orders of magiutude at room temperature. Secondly, graphite is a unique host lattice in that intercalation compounds can be formed with either electron donors or electron acceptors as guest species. 

ZrCl has a homoatomic-layer structure sequenced Cl-Zr-Zr-Cl. Each Zr atom has three neighbours in the adjacent sheet at 3.09 A, six more in the same sheet at 3.42 A and three chlorine atoms on the other side at 2.63 A. Weak chlorine-chlorine interactions between sheets at 3.61 A contrast with the strong metal-metal binding within sheets. These structural features account for the graphitic nature and anisotropic electrical conduction of ZrS. Thermodynamic parameters have been obtained for the reduction of zirconium chlorides. The reaction of ZrC with a melt containing alkali-metal chlorides and titanium chlorides has been investigated. ... 

Metal-chain complexes containing stacked square-planar tetracyanoplatinate groups, [Pt(CN)4]2", are currently of high interest because of their one-dimensional (very anisotropic ) metallic properties. Complexes of this type contain metal-atom chains and often possess a characteristic brilliant, metallic luster. They may be synthesized by oxidation using chemical or electrolytic techniques.1 Although these compounds often appear metallic, they may also be semiconductors. These complexes differ in their Pt-Pt intrachain separations, degree of partial oxidation of the platinum atom (Pt2-1 2 4), electrical conductivity, and metallic color.2 Compounds in this series which contain platinum atoms in a nonintegral oxidation state are known as partially oxidized tetra-cyanoplatinate (POTCP) complexes. Some complexes also possess a metallic luster but are not metallic, as is the case for Tl4(C03)[Pt(CN)4] (see below). 

In planar transition metal complexes, the interactions among the metal and ligand tt orbitals which occur within these stacks can provide a continuous pathway for electron delocalization along one direction in the solid which is detectable as anisotropic electrical conductivity. Such effectively one-dimensional solid-state interactions can result in unique properties and property combinations. 

Fig. 8 Double logarithmic plot of ionic and electronic conductivity, /C on and k, of oxide films. Dotted line ionic conductivity equals the electronic one. Arrows indicate changes due to increasing field, approaching Ufb and increasing electronic equilibrium. Passive Ti as example 1 stable passive film of Ti02 near the flat band potential 2 insulating film of Ti02 on anisotropic metal plane (xxxO) 3 as 2, but for the isotropic, close packed metal plane (0001).

Part II surveys the inorganic materials which exhibit or potentially exhibit a columnar structure. Emphasis is placed on square planar third-row transition metal complexes which exhibit the properties of anisotropic electrical conductivity and the first-row transition metal complexes which exhibit anisotropic cooperative magnetic behavior. The measured chemical and physical properties of the known one-dimensional inorganic complexes are summarized and a number of potentially one-dimensional materials are surveyed. The known one-dimensional magnetic systems are then presented. An extensive reference list including citations through the beginning of 1975 is included to make it easy for the reader to go further into areas of his particular interest. 

Metallic conductivity, superconductivity, and cooperative magnetic properties are the most significant attributes of these donor-acceptor (and partial charge transfer) solids." These properties derive from the partially occupied delocalized n-orbitals of the donor and acceptor species, which overlap to form energy bands along the stacks. Interactions between the stacks are less important, as the conductivities are usually anisotropic. Enlargement of the donor and acceptor species diminishes the coulombic destabilization of stacks of homo-(partially)-charged molecules. 

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