P. Varotsos | Searcharxiv

arXiv2017

Interconnection of point defect parameters in solids with bulk properties: A review

Two models have been proposed for the interconnection of the defect Gibbs energy g^i with bulk properties almost 60 and 30 years ago, respectively. The one, proposed by Zener, assumes that g^i can be accounted for the work that goes into straining the lattice and hence it is proportional to the shear modulus of the solid. The other, considers that, since g^i corresponds to an isobaric and isothermal process, it should be proportional to the isothermal bulk modulus and the mean volume per atom. The results of these two models are compared for different processes (defect formation, self-diffusion activation, hetero-diffusion) in a variety of solids including metals (fcc, bcc and tetragonal) as well as solids that exhibit superionic behavior. We find that the latter model does better than the former.

cond-mat.mtrl-sci↗

arXiv2006

Attempt to distinguish the origins of self-similarity by natural time analysis

Self-similarity may originate from two origins, i.e., the process memory and the process' increments ``infinite'' variance. A distinction is attempted by employing the natural time χ. Concerning the first origin, we analyze recent data on Seismic Electric Signals, which support the view that they exhibit infinitely ranged temporal correlations. Concerning the second, slowly driven systems that emit bursts of various energies E obeying power-law distribution, i.e., P(E) ~ E^-γ, are studied. An interrelation between the exponent γand the variance κ_1(= <χ^2> - <χ>^2) is obtained for the shuffled (randomized) data. In the latter, the most probable value of κ_1 is approximately equal to that of the original data. Finally, it is found that the differential entropy associated with the probability P(κ_1) maximizes for γaround 1.6 to 1.7, which is comparable to the value determined experimentally in diverse phenomena, e.g., solar flares, icequakes, dislocation glide in stressed single crystals of ice e.t.c. It also agrees with the b-value in the Gutenberg-Richter law of earthquakes.

cond-mat.stat-mech↗