Lateral packing hexagonal lattice

The hydrocarbon chain-packing modes are usually described by means of a subcell, which gives the symmetry relations between equivalent positions in one chain and its neighbors [9,10]. Four types of subcells have been identified (1) The planes contain parallel hydrocarbon chains, (2) the chains are perpendicular to each other, (3) the chain axes are crossed, and (4) the chains are packed in a hexagonal lattice. By lateral repetition of the subcell, the entire structure of the chain region is obtained. Structural analysis of normal paraffins with more than nine carbon atoms in the chain revealed mainly four possible distinct crystal structures hexagonal, triclinic, monoclinic, and orthorhombic [11]. 

UMEs are usually arranged in a regular pattern to form an array. Multitudes of parallel UMBEs are present in an IDA electrode. Disks or square shaped UMEs can be arranged in a square or hexagonal lattice. Randomly distributed UMDEs—if they are not too closely packed—can be modelled by estimating the nearest-neighbour distribution [342] and statistical considerations, as has been done by Scharifker [343] and later by Compton et al. [344-348] and others [77, 349]. The next section looks into the simulation approach for regular arrays of UMDEs. 

A second structure to consider is a synthetic nanowall structure consisting of a closely packed forest of CNTs patterned into walls, on a square, hexagonal or triangular lattice (Fig. 13.6) [35]. These also allow for emission site redundancy. They have the added advantage that they can accommodate the lateral ballast resistor between a current source and the emitting walls. 

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