Graphite surfaces, interaction

In the previous section the interaction of the plasma particle flux with the surface of graphite was discussed. However, the fate of the implanted particles (most importantly deuterium and tritium) following their impact with the graphite surface is also an important issue, and is seen by some as the major impediment to graphite s use as a PFM [58], Quantification of the problem, and determination of possible mitigating steps, is complicated by experimental data which can vary by orders of magnitude [59-66] as reviewed by Wilson [67]. 

The multi-shell fullerenes constitute the transition from fullerenes to macroscopic graphite. They present both the closed graphitic surface of fullerenes and the stacked layers interacting by van der Waals forces, as in graphite. 

A parameterization of many different surface potentials, ranging from (100) surfaces of FCC crystals to graphite surfaces, has been given by Steele [146-148]. Since most of the systems discussed below are adsorbed layers on graphite surfaces, we consider the graphite substrate in detail. The interaction potential between an adsorbate particle at the position r = (x,y, z) and all other substrate particles consists of two contributions,... 

To treat the orientational structure of the monolayer formed by 02 molecules on a graphite surface, allowance must be made for the fact that an oxygen molecule is characterized not only by a nonzero magnetic moment but also by a record small quadrupole moment, so that dispersion interactions prevail over quadrupole interactions at intermolecular distances shorter than 10 A.79 In addition, the adsorbate lattice parameters give rise to very small minimum intermolecular distances, a 3.3 A, the parameter b 8.1 A markedly exceeding the values a. That is why, it is sufficient to consider only the nearest-neighbor interactions in a... 

An alternative efficient approach to disperse CNTs relies on the use of synthetic peptides. Peptides were designed to coat and solubilise the CNTs by exploiting a noncovalent interaction between the hydrophobic face of amphiphilic helical peptides and the graphitic surface of CNTs (Dieckmann et al., 2003 Zoibas et al., 2004 Dalton et al., 2004 Arnold et al., 2005). Peptides showed also selective affinity for CNTs and therefore may provide them with specifically labelled chemical handles (Wang et al., 2003). Other biomolecules, such as Gum Arabic (GA) (Bandyopadhyaya et al., 2002), salmon sperm DNA, chondroitin sulphate sodium salt and chitosan (Zhang et al., 2004 Moulton et al., 2005), were selected as surfactants to disperse CNTs (Scheme 2.1). 

Petit C, Bandosz TJ Enhanced adsorption of ammonia on Metal-Organic Framework / graphite oxide composites analysis of surface interactions, Adv. Fund. Mater. 2009,19,1-8. 

Batra, I. P., and Ciraci, S. (1988). Theoretical scanning tunneling microscopy and atomic force microscopy study of graphite including tip-surface interaction. J. Vac. Sci. Technol. A 6, 313-318. 

Liebsch, A., Harris, J., and Weinert, M. (1984). Interaction of helium with a graphite surface. Surf. Sci. 145, 207-222. 

However, since SCC-DFTB is derived from DFT, it inherits the DFT failures and shortcomings. On the one hand, there is the deficiency of DFT for the description of van der Waals bonded complexes. Here, we extended SCC-DFTB by an explicit treatment of attractive dispersion forces [36], an extension called hereafter SCC-DFTB-D, which has been added to DFT methods in the same way later on as well [37,38], We have shown that this term is crucial not only for the interaction of DNA bases [36,39,40] or DNA intercalators [41,42], but also, for example, for the structure and stability of water on a graphite surface [43] and certain peptide configurations [21,23,44],... 

Monte Carlo simulation techniques are used for calculating the distribution coefficients of benzene between supercritical C02 and slitpores at infinite dilution. The Lennard-Jones potential model is used for representing the pair interactions between C02, benzene, and graphite carbon. The effects of temperature, slitwidth, and benzene-surface interaction potential on the distribution coefficients are explored at constant density and constant pressure. 

Hhere z is the distance from the graphite surface, A is the distance between the Kraphite layers (0.335 nm) and p is the number of carbon atoms per unit volume m4nm 3). The derivation of this 10-4-3 potential function involved integration ver the basal plane and summation over the successive layers. The 10- and 54- terms, therefore, represent the repulsive and attractive interactions with the psal plane, while the 3- term takes care of the summation over the remaining layers. This form of potential function has been favoured in recent computer Ifoulation studies of the adsorption of molecules by porous carbons (Nicholson, 996,1997). 

---