Comments on the Pressure Variation of the Gibbs Energy for Bound and Unbound Defects

Abstract

The pressure derivative v of the Gibbs energy g for "unbound" and "bound" defects (i.e. vacancies or interstitials attracted by aliovalent impurities) is studied. It is shown that for the formation and migration of defects the ratio v/g depends solely on well-known macroscopic properties; applications are presented for self-diffusion in f.c.c. and b.c.c. metals and for ionic conductivity of silver halides. In the case of ionic solids containing "bound" defects, a gradual variation of pressure results in the appearance of a transient polarization or depolarization current that maximizes a t a certain pressure Per. The way of analysing this piezo-stimulated current (PSC) spectrum is discussed. The fact that the value of PCr does not have to coincide with the pressure a t which fracture occurs provides a useful tool for applying PSC to geophysics.Die Druckableitung v der Gibbsschen Energie g fur ,,ungebundene" und ,,gebundene" Defekte (d. h. Vakanzen oder Zwischengitterstorstellen, die durch aliovalente Storstellen angezogen werden) wird untersucht. Es wird gezeigt, daB fur die Bildung und Wanderung der Defekte das Verhaltnis v/g allein von gut bekannten makroskopischen Eigenschaften abhiingt, Anwendungen werden fur die Selbstdiffusion in k.f.z.-und k.r.2.-Metallen und fur die Ionenleitung in Silberhalogeniden angegeben. Fiir den Fall von Ionenfestkorpern, die ,,gebundene" Defekte enthalten, fuhrt eine graduelle h d e r u n g des Druckes zum Auftreten eines nichtstationiiren Polarisations-oder Depolarisationsstromes, der ein Maximum bei einem kritischen Druck P,, annimmt. Die Mdglichkeit einer Analyse dieses piezostimulierten Strom(PSC)-Spektrums wird diskutiert. Die Tatsache, dall der Wert von P,, nicht mit dem Druck ubereinstimmen muB, bei dem der Bruch auftritt. liefert eine nutzliche Methode fur die Anwendung des PSC in der Geophysik.

Seismicity anomalies prior to the 13 December 2008, <i>M<sub>s</sub></i>=5.7 earthquake in Central Greece

“…In other words, "a" seems to be a universal constant originating from the fractal properties of the emitting source. This is so because SES may be emitted when the source enters the critical regime (Varotsos et al, 1982) which is inherently associated with fractality (see 270-272 of Varotsos, 2005). In fact, the following physical mechanism has been proposed for the emission of SES (Varotsos and Alexopoulos, 1984): When the stress increases in the focal region of a future earthquake, it will affect physical properties of the crust including a decrease of e.g.…”

Power law relationship between parameters of earthquakes and precursory electrical phenomena revisited

“…As the pressure increases the relaxation time becomes significantly smaller, provided that the migration volume v=(dg/dP) T (Varotsos et al, 1982 or the activation (Varotsos and Alexopoulos, 1980b) is negative, and when the pressure reaches a critical value, P cr , a transient current is emitted due to the cooperative re-orientation of dipoles .…”

Entropy in Natural Time and the Associated Complexity Measures

“…The criticality of the OFC model has been debated [87,88]. Also, the SOC behavior of the model is destroyed upon introducing some small changes in the rules of the model, e.g., replacing open boundary condition with periodic boundary conditions [89], introducing frozen noise in the local degree of dissipation [90] or in its threshold value [91], including lattice defects [92] (which should not be confused with the intrinsic lattice defects in solids [93], e.g., Schottky [94,95] or Frenkel [96,97] defects). Despite these findings as well as others which show [98] that it is insufficient to account for certain aspects of the spatiotemporal clustering of seismicity, the OFC model appears to show many features found in real earthquakes.…”