Volume changes, with electronic

Marky LA, Kupke DW (2000) Enthalpy-entropy compensations in nucleic acids contribution of electrostriction and stmctural hydration. Meth Enzymol 323 419-441 Masterton WL, Lee TP (1970) A classical model for the low-energy electron(positron)-atomic hydrogen(l s) elastic scattering. J Phys Chem 79 1776-1782 Mathieson JG, Conway BE (1974) Partial molal compressibilities of salts in aqueous solution and assignment of ionic contributions. J Sol Chem 3 455-477 Mauzerall D, Hou J-M, Boichenko VA (2002) Volume changes and electrostriction in the primary photoreactions of various photosynthetic systems estimation of dielectric coefficient in bacterial reaction centers and of the observed volume changes with the Drude-Nernst equation. Photosyn Res 74 173-180... 

MnAs exhibits this behavior. It has the NiAs structure at temperatures exceeding 125 °C. When cooled, a second-order phase transition takes place at 125 °C, resulting in the MnP type (cf. Fig. 18.4, p. 218). This is a normal behavior, as shown by many other substances. Unusual, however, is the reappearance of the higher symmetrical NiAs structure at lower temperatures after a second phase transition has taken place at 45 °C. This second transformation is of first order, with a discontinuous volume change AV and with enthalpy of transformation AH. In addition, a reorientation of the electronic spins occurs from a low-spin to a high-spin state. The high-spin structure (< 45°C) is ferromagnetic,... 

For the mechanistic interpretation of activation volume data for nonsymmetrical electron-transfer reactions, it is essential to have information on the overall volume change that can occur during such a process. This can be calculated from the partial molar volumes of reactant and product species, when these are available, or can be determined from density measurements. Efforts have in recent years focused on the electrochemical determination of reaction volume data from the pressure dependence of the redox potential. Tregloan and coworkers (139, 140) have demonstrated how such techniques can reveal information on the magnitude of intrinsic and solvational volume changes associated with electron-transfer reactions of transition... 

When a gas is compressed, it heats up. When it expands, it cools. Anyone who uses a bicycle pump knows this. However, it is no longer true for electron or neutron gases at very high densities. This deviation from the ideal gas laws has a catastrophic effect on stars. Moreover, the behaviour of a photon gas with regard to volume changes differs from that of a typical gas made up of atoms,... 

These equilibrium reactions occur with large decreases in both volume and entropy. Volume changes range from —80 to —300 cm /mol depending on the solute and pressure. These volume changes, A V, are associated with the electrostriction of the solvent around the product anion, Fei(ion), and, to some extent, with a contribution of the partial molar volume of the electron, V(e). Thus ... 

Studies of the effect of pressure on /iq for nonpolar liquids provided support for the two-state model. Pressure affects the position of the equilibrium [Eq. (23)] because of the volume change associated with trapping of the electron, A Ftr- These volume changes were deduced from changes in /td with pressure. For -alkanes [157] as well as some al-kenes [158], the mobility decreases with pressure, as shown in Fig. 11 for -hexane and 1-pentene. 

For certain liquids like cyclohexene [158], o-xylene, and m-xylene [159], the mobility increases with increasing pressure (see Fig. 11). These results provided the key to understand the two-state model of electron transport. In terms of the model, AFtr is positive for example, for o-xylene, AFtr is +21 cm /mol. Since electrostriction can only contribute a negative term, it follows that there must be a positive volume term which is the cavity volume, Fcav(e). The observed volume changes, AFtr, are the volume changes for reaction (23). These can be identified with the partial molar volume, V, of the trapped electron since the partial molar volume of the quasi-free electron, which does not perturb the liquid, is assumed to be zero. Then the partial molar volume is taken to be the sum of two terms, the cavity volume and the volume of electrostriction of the trapped electron ... 

---