The Meyer-Neldel Rule
This phenomenon (also known as the Compensation Effect) can occur in any situation which involves an activated process. However, the rule is still most commonly referred to in connection with diffusion phenomena. As the rule still tends to exist in a sort of limbo between fully accepted physical law and unexplained correlation, this volume presents a handy survey of relevant diffusion data reaching back as far as the 1930s.
This shows that most of the huge amount of available data (closely monitored by this journal for some 35 years) is unsuitable for giving a clear-cut answer concerning the significance of the Meyer-Neldel rule. A major difficulty is that such data were usually determined with some other aim in mind and are not intrinsically well-suited to the testing of the Meyer-Neldel relationship. Different laboratories, using standard methods, are very likely to obtain very similar Arrhenius parameters: too similar, in fact, to test the rule properly.
Nevertheless, an extensive data-base and analysis is presented for those relatively few systems in which the rule can be tested over reasonable ranges of pre-exponential factor and activation-energy values. In some cases, the rule seems to be adhered to very closely by a good number of independent data-points. Original papers are also included which discuss the statistical shift model for the rule, and its relationship to the kinetic properties of grain and interphase boundaries. Other papers consider the incidence of the rule in the hopping mobility of amorphous polymeric materials, and in the persistent photoconductivity of an organic semiconductor.