Zero gap

It is clear from Figure 6.8 that the band for each isotope is fairly symmetrical about the corresponding band centre and that there is approximately equal spacing between adjacent i -branch lines and between adjacent P-branch lines, with twice this spacing between the first R- and P-branch lines, R(0) and P(l). This spacing between R(0) and P(l) is called the zero gap and it is in this region where the band centre falls. 

From Equations (6.27) and (6.28) it follows that the zero gap, v[i (0)] — v[P(l)], is AB and that the spacing is 2B between adjacent i -branch lines and also between adjacent P-branch lines, hence the approximate symmetry of the band. 

These surprising results can be understood on the basis of the electronic structure of a graphene sheet which is found to be a zero gap semiconductor [177] with bonding and antibonding tt bands that are degenerate at the TsT-point (zone corner) of the hexagonal 2D Brillouin zone. The periodic boundary... 

Lombos BA, Lee EYM, Kipling AL, Krawczyniuk RW (1975) Mercury Chalcogenides, Zero gap semiconductors. J Phys Chem Solids 36 1193-1198... 

A zero-gap electrolyser is currently under trial. In pilot-scale operation, it has demonstrated a cell voltage of 3.0-3.1 V at a current density of 6 kA m-2. The results indicate that completion of zero-gap technology will bring a further reduction in unit power consumption of 100 kWh per tonne of NaOH. 

BiChlor contains a number of features to lower the electrolyser voltage by reducing the resistance. One of these features is the design for zero gap operation. This lowers the electrolyser resistance by keeping the distance from the electrodes to the membrane at a minimum. 

Figure 7.2 Cell designs, (a) Conventional alkaline electrolysis (b) advanced alkaline electrolysis (zero gap) (c) SPE configuration (acid electrolysis).

The problem of ohmic drops has recently been tackled by modifying the cell design. This is a matter of engineering, not of chemistry. The conventional design of divided cell has been replaced with a so-called zero-gap configuration [15], where the... 

Katayama S, Kobayashi A, Suzumura Y (2006) Pressure-induced zero-gap semiconducting state in organic conductor a-(BEDT-TTF)2l3 salt. J Phys Soc Jpn 75 054705/1-6... 

Due to its zero-gap electronic stmcture, large graphene sheets are not suitable for FET applications [185, 193]. It has been shown that graphene transistors conduct current even at the point of expected isolator behavior (i.e., Dirac point) [288]. Therefore, current modulation cannot be achieved using macroscopic graphene sheets [185]. In order to have a band gap on graphene, the use of narrow ribbons of... 

The initiation delay has been also measured for several solid expls when sub-j ected to a relatively weak shock stimulus generated by an HE and attenuated by a rubber barrier. The delay was found to be dependent on the barrier thickness, at least for the geometry employed. For a zero gap... 

So-called zero-gap membrane cells in which cathode and chlorine-evolving anodes are touching the cation exchange membrane, which separates the anode from the cathode compartment, are also state of the art (35). Bipolar chlorine electrolyzers have also been developed (36), for instance, at ICI, an achievement that could only be envisaged due to the introduction of RuCL-coated titanium anodes. 

Bipolar ED. Bipolar ion-exchange membranes have one surface consisting of CX resin and the opposite surface of AX resin. The interface between the CX and AX resins may be regarded as a zero gap ED compartment. When a direct current is passed through such a membrane in a direction to pull anions out of such interlace and through the AX resin, the interface rapidly becomes depleted of all ions other than those resulting from the dissociation of water. Dilute alkali can therefore be produced at the outer surface of the AX region and dilute acid at Ihc outer surface of the CX layer. 

Next, the zero-gap reference position (the contact point where the stator and the rotor just touch) should be set using the software routines for bringing rotor and stator into contact. After this, the gap used for the test itself can be set. Generally, the zero-gap referencing procedure should be done at the temperature of interest for testing. Some instruments control temperature using an environmental chamber or oven, whereas others will heat or cool the stator. If the latter is the case, then for temperatures that are well away from ambient, the gap can be referenced at ambient and the temperature of interest set with the sample in place to aid thermal conductivity. This is reasonable if the instrument has a gap temperature compensation factor. Most autogap instruments will have this facility built into the firmware that controls the rotor position with respect to the stator. 

There are several methods for referencing the zero gap. The deceleration of the rotor as it spins is used by some instruments others use an electrical circuit between the rotor and... 

Our results with PITN are very encouraging to the development of an organic semimetal (zero gap semiconductor) since a relatively minor modification allowed to reduce the energy gap within a family of poly(heterocycles) by 1 eV (23 Kcal). Further modifications by annulation and substitution (electron donor or acceptor) are expected to further reduce the energy gap of a PT-based polymeric conductor. We are currently actively engaged in the preparation of such neutral organic conductors. 

Fig. 65 Temperature dependence of magnetic functions (level-6) for different axial crystal-field strength F z) of Mn(III) complexes. From left to right Ffxy) = 4000, 8000, 13000, and 18000 cm Black lines refer to the regular octahedron with non-zero gap < 14. Note temperature axis runs oppositely between the top and bottom panels...

Let us recall that nanotubes can be considered as graphene sheets rolled up in different ways. If we consider the so-called chiral vectors c = nai + na2, in which a and a2 are the basis vectors of a 2D graphite lattice, depending on the value of the integers n and m, one can define three families of tubes armchair tubes (n = m), zig-zag tubes (n or m = 0), and chiral tubes (n m 0). Band structure calculations have demonstrated that tubes are either metallic compounds, or zero-gap semiconductors, or semiconductors [6,7]. More commonly, they are divided into metallic tubes (when n-m is a multiple of 3) or semiconducting ones. 

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