One-dimensional materials

Plenary 6. Shu-Lin Zhang et al, e-mail address slzhang pku.edu.cn (RS). Studies of phonon modes of nanoscale one-dimensional materials. Confinement and defect induced Raman transitions. 

Memory requirements for one-dimensional eontinuum dynamies ealeulations are minimal by the standards of eurrent hardware. Thus, sufTieiently fine zoning ean be used in sueh ealeulations to eapture details of material response and provide a rigorous test of fidelity for the numerieal models employed. The ability to use fine zoning also ensures that any diserepaneies between ealeulation and experiment ean be attributed, with eonsiderable eonfidenee, to Inadequaeies in the material response model. In faet, most desktop workstations have suffieient eomputing horsepower and memory to meet the eom-putating needs in one-dimensional material response studies. 

Carbon nanotubes have the same range of diameters as fullerenes, and are expeeted to show various kinds of size effeets in their struetures and properties. Carbon nanotubes are one-dimensional materials and fullerenes are zero-dimensional, whieh brings different effects to bear on their structures as well as on their properties. A whole range of issues from the preparation, structure, properties and observation of quantum effeets in carbon nanotubes in eomparison with 0-D fullerenes are diseussed in this book. 

Preparation research of SWCNT was also put forth by lijima and his co-worker [3]. The structure of SWCNT consists of an enrolled graphene to form a tube without seam. The length and diameter depend on the kinds of the metal catalyst used in the synthesis. The maximum length is several jim and the diameter varies from 1 to 3 nm. The thinnest diameter is about the same as that of Cgo (i.e., ca. 0.7 nm). The structure and characteristics of SWCNT are apparently different from those of MWCNT and rather near to fullerenes. Hence novel physical properties of SWCNT as the one-dimensional material between molecule and bulk are expected. On the other hand, the physical property of MWCNT is almost similar to that of graphite used as bulk [6c]. 

The presence of zinc with bidentate nitrogen donor ligands in the formation of novel composite materials by hydrothermal reactions has been studied. A zinc-containing one-dimensional material, [Zn(phenanthroline)Mo04] was isolated from molybdate, and from vanadium oxide in the presence of zinc 2,2 -bipyridine [Zn(2,2,-bipyridine)2V40i2] was obtained.212,213... 

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. 

One-dimensional material balance for water in soil may be written [8]... 

Much of the Pt2n chemistry came about as a result of the serendipitous discovery of the first platinum pyrimidine blue , formed from cis-[Pt(NH3)2(H20)2]2+ and polyuracil left incubating for several days at pH 7 and 37 °C. This material proved to have high antitumor activity as well as low renal toxicity [1-4], However, interest in Ptin chemistry [5-10] also arises from its possible occurrence in mixed-valence one-dimensional materials [11] [12] and from the participation of Ptm in Ptn/PtIV redox processes [13], as well as in the photocatalytic activation of C-M and C-X bonds [14],... 

Nanowires constitute a major family of one-dimensional materials. Besides confinement, they exhibit several interesting properties. Inorganic nanowires can be prepared by several methods. A few articles dealing with the synthesis, characterization and applications of inorganic nanowires are presented. Growth mechanism of nanorods has been examined in one of the article. 

In general, then, a band which is 1/3,1/4. .. l/p occupied is subject to Peierls instability with respect to a tri-, tetra-, / -merisation. It is important to remind you at this point that the possibility of a Jahn-Teller instability does not always mean the distortion occurs. The same applies for Peierls instability. There are several reasons. First of all, Peierls instability holds rigorously for ideal one-dimensional materials and reality is a more complicated three-dimensional space. Second, as in the case of molecules, when high-spin states are preferred, the distortion is not favored (see Problem 7 for an example). Third, even in the case of low-spin systems, the distortion may have additional consequences, e.g., weakening of spectator bonds. Coupled destabilizing effects can dampen or even prevent distortion. In the H2 case described above, there is no effect opposing the distortion, and dimerization is complete, i.e., fully independent H2 molecules result from our hypothetical chain. 

The replacement of main-group atoms in clusters by transition-metal atoms generates a richer structural chemistry superimposed on the cluster basics illustrated by the p-block systems. A logical question arises here. What would a one-dimensional material containing a transition metal look like Well, the d AOs will generate bands in a similar manner as the s and p orbitals. The major novelty will be the introduction of orbitals of 8 symmetry. Let s look at a hypothetical chain composed of equidistant Ni atoms (d = 2.5 A). The computed band structure, DOS and COOP are illustrated in Figure 6.14. The COs at k = 0 and ir/d arc drawn below. As a review of the previous section, we will reconstruct it starting from the Bloch functions associated with the nine Ni AOs. 

A development in the use of structured Ti02 has been the production of new one-dimensional materials such as nanotubes, nanofibers, and nanowires [86-... 

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. 

In order to test such a hypothesis, highly ideal model one-dimensional materials are required, since any interaction between chains must be minimised to enable Haldane Gap behaviour to be observed and studied. The molecular magnetic material [Ni(jU-N3)(l,3-diamino-... 

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... 

The contemporary interest in metal organophosphonate coordination chemistry has received considerable impetus from the applications of such materials as sorbents, catalysts and catalyst supports. The structural chemistry of the metal organophosphonate system is extremely rich " and is represented by mononuclear coordination complexes, molecular clusters, " one-dimensional materials, and layered phases. Extensive investigations have been reported on layered phosphonates of divalent, " trivalent, tetravalent, " and recently hexavalent elements. Several examples of three dimensional metal organophosphonate frameworks have also been described since the first report by Bujoli. " ... 

Quantum size effects related to the dimensionahty of a system in the nanometer range suggests a plethora of future applications using novel material properties. Whereas three-dimensional systems have an infinite extent in all three directions, in layered systems, for example atomic monolayers and thin films, the dimensionality is two, i.e. they are characterized by a limited number of layers. Consequently, a one-dimensional material is represented by wires on an atomic or molecular scale and may be realized in fibers or polymers. Zero-dimensional particles are reduced in all directions to such an extent that the properties of the original bulk system cannot... 

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