Lattice breakdown

Taylor [648] has shown that the deceleratory decomposition of HgO is satisfactorily described by the contracting volume equation [eqn. (7), n = 3], Calculated values of E (162—201 kJ mole rise with increasing crystallite size and are somewhat greater than the enthalpy of dissociation (160 kJ mole 1). Since estimated values of A are consistent with the predictions of the Polanyi—Wigner equation, eqn. (19), it is concluded that breakdown involves the detachment of individual molecules rather than the unzipping of the long zig-zag polymeric —Hg—O— chains which constitute the reactant lattice. 

When, however, phonons of appropriate energy are available, transitions between the various electronic states are induced (spin-lattice relaxation). If the relaxation rate is of the same order of magnitude as the magnetic hyperfine frequency, dephasing of the original coherently forward-scattered waves occurs and a breakdown of the quantum-beat pattern is observed in the NFS spectrum. 

Given the character of the water-water interaction, particularly its strength, directionality and saturability, it is tempting to formulate a lattice model, or a cell model, of the liquid. In such models, local structure is the most important of the factors determining equilibrium properties. This structure appears when the molecular motion is defined relative to the vertices of a virtual lattice that spans the volume occupied by the liquid. In general, the translational motion of a molecule is either suppressed completely (static lattice model), or confined to the interior of a small region defined by repulsive interactions with surrounding molecules (cell model). Clearly, the nature of these models is such that they describe best those properties which are structure determined, and describe poorly those properties which, in some sense, depend on the breakdown of positional and orientational correlations between molecules. 

The second major contrast mechanism is extinction contrast. Here the distortion of the lattice arotmd a defect gives rise to a different scattering power from that of the surrotmding matrix. In all cases, it arises from a breakdown or change of the dynamical diffraction in the perfect ciystal. In classical structure analysis, the name extinction was used to describe the observation that the integrated intensity was less than that predicted by the kinematical theoiy. 

The behavior of the fluorosulfinate as an activated alkali fluoride is readily explained in terms of a widening of the fluoride crystal lattice, and the amount of energy required for its breakdown in fluorinations is accordingly lower. 

The release of cations is interpreted to have resulted chiefly from two processes an initial release caused by rapid exchange of surface cations for hydrogen followed by a slow release due to structural attack and disintegration of the aluminosilicate lattice. Other processes which could complicate the form of the dissolution curves are adsorption of cations released by structural breakdown, ion exchange on interlayer sites of cations released by structural breakdown and surface exchange (shale only), precipitation of amorphous or crystalline material, and dissolution rate differences among the various crystalline phases. 

Breakdown of contributions to coefficient an for specific heat series of Ising mode, fee lattice (Data of M. F. Sykes.)... 

Clathration is the third sorption situation. Guests are incorporated during the growth of the host lattice. Their liberation occurs on heating or lowering the pressure with lattice breakdown. This situation is found for water, phenol, quinol, cresol, urea, and Dianin s compound. 

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