Organic molecular crystals direct measurements

The solid curves in Fig. 8.37 were computed with only one free parameter in Eq. (8.67), namely the longitudinal velocity of sound = 4 10 cm/s. /xq is not a fit parameter, since the zero-field mobility follows directly from the measurable slope of vd(F) for F 0 (see Fig. 8.37). The value for ce obtained in this way agrees surprisingly well with the independently-measured longitudinal sound velocity (compare Table 5.4) and is thus a good indication that the Shockley model for the electron-phonon coupling is also applicable to organic molecular crystals. 

The behavior of real component powders may be estimated using a yield criterion (1), which requires a knowledge of the magnitudes of the directional response to stress of the particle and knowledge of the particle size distribution and particle orientation. Much of this information is not readily available for molecular organic solids and is the subject increasing attention of academic materials scientists. Even knowing the crystal structure, the dynamic response to mechanical stresses is not currently predictable without exhaustive effort (3). However, yield behavior may be measured and correlated to the... 

The crystal and molecular structure of p-adenosine-2 -p-uridine-5 -phosphoric acid precipitated from aqueous solution ° shows that water molecules serve as a major part of the binding force between the nucleotide molecules. In this instance hydrogen bonds do not directly link the bases together. Webb and Bhorjee, using infrared measurements to study factors influencing viability and conformation, reiterate the importance of water in maintaining an organized structure for DNA from E. coli. 

---