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The temperature dependence of the thermodynamic and the elastic properties of elemental gold are found from published data. It is shown that measurements for (∂KT/∂P)T near 5.5 are more thermodynamically consistent than are higher values of this parameter which have been reported earlier. Using 5.5 for (∂KT/∂P)T, we find that (∂KT/∂T)V is not zero but −11.5×10−3 GPa K−1 for high temperatures (T>θD, where θD is the Debye temperature). One consequence of this is that above θD the thermal pressure, PTH, along the room-pressure isobar can be expressed as PTH(T)−PTH(300)=[7.14×10−3 +(∂K T/∂T)v ln(Va/V)] ×(T−300) GPa for T at absolute temperature and Va being the volume at ambient conditions. These results give thermal pressure values near those previously reported at small compressions, but give lower thermal pressures at large compressions. This study suggests that in order to ensure thermodynamic consistency, the value of d ln γ/d ln V is near 2.5–3.0 which is higher than values of 1.0 and 1.7 reported previously (γ is the Grüneisen ratio). Calculations giving the compressional and shear wave velocities, vp and vs, are also presented. One result is that the quantity ∂ ln vs/∂ ln vp at constant pressure is about 1.85 and is independent of temperature.

An equation for the activation energy of ionic conduction in silica glasses is developed. The approach uses the classical ideas of ionic crystal theory and elasticity theory. The equation finally derived involves the radius and valence of the modifier ion, the lattice constant of the glass, the electronic charge, the shear modulus, and three arbitrary parameters. Two of these parameters are shown to be related to the geometry of the silica network and are exactly determined from difiusion of gases in glass data. The other parameter is shown to be approximately numerically equal to the dielectric constant.The theory is compared with the experimental results of 140 glass compositions.

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Ultrasonic wave velocities in single-crystal forsteritc (F) and single-crystal olivine (0) have been measured as a function of pressure and of temperature near ambient conditions. Shear and longitudinal velocities were measured in eighteen independent modes, so that each of the nine elastic constants could be calculated by at least two independent equations. The adiabatic stiffness constants c{j (in Mb), their temperature derivatives dc,j/dT (10 -4 Mb/ deg), and their pressure derivatives dc{ffdP, are ij 11 22 33 44 55 66 23 31 12 Cii (F) 3.284 1.998 2.353 0.6515 0.8120 0.8088 0.738 0.688 0.639 (O) 3.237 1.976 2.351 0.6462 0.7805 0.7904 0.756 0.716 0.664 2Now at: by Verma [1960], who presented the secondorder elastic constants of a single crystal. A few reports have been made on the isotropic elastic constants of polycrystalline aggregates of forsteritc made by hot-pressing ([Schreiber and Anderson, 1967] and Marsh (personal communication, 1969) ). Our purpose here is to present our measured values of the elastic constants, their pressure derivatives at room temperature, and their temperature derivatives at i atm; to describe the methods of measurements on a crystal of orthorhombic symmetry; and to list a number of physical constants derived from the basic data.The technique used to measure sound velocity is known as the pulse superposition technique [McSkimin, 1961], and has been 5961 5962

The theory of stress corrosion for slow crack propagation is reviewed in the light of classical Griffith theory of fracture. Experimental data for stress corrosion cracking for glasses, ceramics, and metals are reviewed. We suggest that stress corrosion cracking plays an important role in the intrusion of magmas and in the transport of magmas upward through the lithosphere. It is shown that the effect of decreasing temperature (at progressively shallower levels along the geotherm) would be to decrease the crack velocity by several orders of magnitude if other factors were equal. We also propose that stress corrosion may be an important process in time-dependent earthquake phenomena such as premonitory behavior and earthquake aftershocks. We suggest that slow cracking in the earth is not seismically detectable but may nevertheless precede the terminal (catastrophic) phase of the fracture that is discerned as an earthquake.

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