Graphite, dispersion curve

Figure 2. Consistency curve of 13 vol. % graphite dispersed in a water gel using a cone and plate viscometer...

This simple model is sufficient to reproduce properties such as crystal structure, vibrational frequencies, dispersion curves, and elastic constants [40-43], These calculations were applied also to other organized media such as monolayer gaseous films on graphite [44,45], liquid crystals, and Langmuir Blodgett films. 

Diamond has been studied by coherent INS [16]. Fig. 11.7 shows the dispersion curves calculated by periodic DFT these are in excellent with the experimental data. Fig 11.8 shows a comparison of the INS spectrum derived from the dispersion curves and the TFXA experimental spectrum. Examination of the atomic displacements shows that the spectrum can be approximately described as C-C stretching modes above 1000 cm and deformation modes below 1000 cm. The agreement is good except for the features at 154 and 331 cm. These are not a failure of the calculation but are a consequence of the use of graphite for the analysing crystal ( 3.4.2.3) and will be discussed in 11.2.2. 

Graphite has been extensively studied by coherent INS [17,18], HREELS [19,20] and inffa and Raman spectroscopy [21]. Calculated dispersion curves are shown in Fig. 11.9 and the derived INS spectrum and the experimental spectrum in Fig. 11.10. As with diamond the... 

Fig. 11.10 INS spectrum of graphite derived from the dispersion curves of Fig. 11.9 (dashed line) compared with the experimental spectrum as recorded on TOSCA (lower solid line) and MARI (upper solid line).

C. Oshima, T, Aizawa, R. Souda, Y. Ishizawa Y. Sumiyoshi (1988). Solid State Commun., 65, 1601-1604. Surface phonon-dispersion curves of graphite(OOOl) over the entire energy region. 

The internal modes of typical molecular crystals show little dispersion and a calculation of the frequencies at the F point in the Brillouin zone is usually sufficient for good agreement between observed and calculated spectra. However, there are many examples where significant dispersion is present the alkali metal hydrides ( 6.7.1), graphite ( 11.2.2) and polyethylene ( 10.1.1.1) being notable cases. In these instances, a calculation of the full dispersion curves are needed. In... 

Figure 1. Electrode potential curves obtained from the (intermittent) galvanostatic charge-discharge curves of the carbon-dispersed composite electrodes of (a) Lii. sNiOa, (b) Lii Co02, (c) Li6V20s, (d) Lii+6[Ti5/3Li /3]04, and (e) graphite. Reprinted from (1999), (2001), and (2001), with permission from Elsevier Science.

A classical curve, published by Isirikyan and Kiselev (1961) showing the variation of enthalpy of adsorption of n-hexane on a graphitized carbon black at 20 °C, is as shown in Figure 4.43. Values of A// (calmoU ) initially decrease as the sites of highest adsorption are occupied first. As the monolayer is established, so the dispersion forces between the adsorbed molecules of n-hexane increase in magnitude reaching a maximum on completion of the monolayer. 

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