Quasi-one-dimensional material

Organic solids have received much attention in the last 10 to 15 years especially because of possible technological applications. Typically important aspects of these solids are superconductivity (of quasi one-dimensional materials), photoconducting properties in relation to commercial photocopying processes and photochemical transformations in the solid state. In organic solids formed by nonpolar molecules, cohesion in the solid state is mainly due to van der Waals forces. Because of the relatively weak nature of the cohesive forces, organic crystals as a class are soft and low melting. Nonpolar aliphatic hydrocarbons tend to crystallize in approximately close-packed structures because of the nondirectional character of van der Waals forces. Methane above 22 K, for example, crystallizes in a cubic close-packed structure where the molecules exhibit considerable rotation. The intermolecular C—C distance is 4.1 A, similar to the van der Waals bonds present in krypton (3.82 A) and xenon (4.0 A). Such close-packed structures are not found in molecular crystals of polar molecules. 

Thus, inter-atomic distances and the atomic state in Tetracarbon are fundamentally different from all the known forms of carbon. The differences between clear and hard diamond on the one hand, and soft and black graphite on the other hand, illustrate the differences among Tetracarbon and other forms of carbon. The distance between the neighboring sp -carbon atoms within the Tetracarbon chain is about 1.3 A, whereas the distance between the carbon chains is 4.80-5.03 A. It is interesting to note that in some respects Tetracarbon is similar to tubulenes, as it can be considered as tubulene in the limit when the diameter of the tube approaches the diameter of carbon atom. Nevertheless, in Tetracarbon the hybridization state of carbon atoms changes from sp to sp. It is basically a new purely one-dimensional sp -carbon modification with one-dimensional electron band structure, whereas tubulene is a quasi-one-dimensional material in which the number of one-dimensional electron bands increases with increasing tubulene diameter. Tetracarbon and tubulene are also similar in that the carbon chains in Tetracarbon are oriented normally to the surface of the film, similar to the orientation in tubulene. 

The fact that the bare coupling is short-ranged, or more precisely, that its anisotropy is roughly the same as that of the electronic band, is important in order to understand the very existence of quasi-one-dimensional materials. If the electron band is quasi-one-dimensional, such will also be the bare electron-phonon matrix element. E. g. band... 

DISORDERED QUASI-ONE-DIMENSIONAL MATERIALS MORREL H, COHEN... 

I have been collaborating in a series of investigations of the theory of quasi-one-dimensional materials the results of which are as yet largely unpublished. Accordingly, I shall review several of these for the present conference ... 

Here it has been supposed that we are dealing with a quasi-one-dimensional material... 

Bloch, Weisman, and V.arma called attention to the importance of disorder for the electronic properties of quasi-one-dimensional materials, pointed out that there existed x-ray evidence for disorder in a number of such materials, and interpreted the conductivity in terms of Mott hopping in one dimension. Among the materials they considered are NMP-TCNQ, Q-(TCNQ)2, and Ad-CFCNQ. Bulaevskii et al. have measured the magnetic susceptibility of these materials and found them to be strongly paramagnetic at low temperatures with a temperature dependence of the form... 

Some quasi-one dimensional materials have a curious low-temperature structure along the chains of highly overlapping molecules or atoms, both... 

Conducting polymers are considered to be quasi-one-dimensional materials. To be able to study the intrinsic properties of these materials, such as intra- and inter-chain electron motions, it is important to reach a high degree of orientation of the polymer chains. Orientation is also important for achieving a high conductivity in these materials, since an increased order also increases the overlap of orbitals between chains, and thus increases the hopping probability. 

K. Kaneto, K. Yoshino and Y. Innshi in Electronic Properties of Inorganic Quasi-One-Dimensional Materials, Volmne II, Ed., P. Monceau, Dordrecht, Netherlands, 1985, 69. 

Y. Ono, A. Terai, and H. Takayama (eds.). Nonlinear E.xcitations in Quasi-One-Dimensional Materials, Soliton and Its Relevance, Prog. Theor. Pins. Suppl. 113 (1993). 

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