Temperature Dependence Of Self-diffusion Coefficient Research Articles

Cluster approach to the problems of diffusion and viscosity in supercooled states of glycerol-like liquids

To explain the temperature dependence of self-diffusion coefficients, static shear viscosity, and electrical conductivity of highly viscous electrolytes, the cluster representations developed by the authors are used. The interconnection of the enumerated transport coefficients with the most important kinetic characteristic of supercooled states – the lifetime of weakly bound clusters – is established. Internal self-consistency of the proposed formulas and their accord with experimental results is discussed. Interpretation of Vogel–Tamman–Fulcher temperature relationship is given.

Full-potential calculations of the temperature dependence of self-diffusion coefficients : application to Cs

The change in slope of the Arrhenius curve for the diffusion coefficient as a function of temperature is discussed and its occurance is explained by vacancies concentration dependence of the formation energy. It is shown that a sign of the mixing energy parameter of the regular solid solution of vacancies in pure metals is closely connecterd with the sign of the curvature of the diffusion plot. For the analysis of this plot as well as for the estimation of other parameters of self diffusion of bcc Cs we used the total energy calculations based on the Full Potential LMTO method

Temperature dependence of self-diffusion coefficients: Application to Cs

The change in slope of the Arrhenius curve for the diffusion coefficient as a function of temperature is discussed, and its occurence is explained by vacancies concentration dependence of the formation energy. It is shown that a sign of the mixing energy parameter of the regular solid solution of vacancies in pure metals is closely connected with the sign of the curvature of the diffusion plot. For the analysis of this plot as well as for the estimation of other parameters of self diffusion of bcc Cs we used the total energy calculations based on the Full Potential LMTO method.

Ion exchange in zinc selenide crystals: the role of lattice-misfit-induced stresses and dislocations

A new method has been applied to form Cd u Zn 1− u Se solid solutions: ion exchange in the melts of salts. The regularities and specific features of ion exchange processes Cd 2+ ⇄ Zn 2+ in ZnSe powder and single crystal plates have been studied. Cd u Zn 1− u Se solid solution obeys the model of regular solution. Temperature dependences of equilibrium constant and interaction energy of strained and unstrained Cd u Zn 1− u Se solid solutions have been defined. We proposed the model taking into account the role of lattice-misfit-induced stresses and dislocations in the ion exchange equilibrium. The depth profiles of elements in the ion exchanged Cd: ZnSe single crystal structures were analysed and temperature dependences of self-diffusion coefficients of Zn 2+ and Cd 2+ and Cd 2+ ions were determined.

ChemInform Abstract: Anisotropy of Translational Diffusion in Liquid α,ω‐Dibromoalkanes

The analysis of the measured temperature dependences of self-diffusion coefficients for prolate ellipsoid type molecules of α,ω-dibromo-methane, -ethane, -octane, -decane and -dodecane performed in the frame of the modified Perrin model enabled to discover anisotropy of translational diffusion in liquids. On the basis of the Eyring theory the effect was confirmed and the jump length of about 7 A for all the molecules was derived. The same jump length for longer molecules was obtained from the Cohen-Turnbull free volume theory.

Molecular weight and temperature dependence of self-diffusion coefficients in polyethylene and polystyrene melts investigated using a modified n.m.r. field-gradient technique

Self-difusion in polyethylene and polystyrene melts has been investigated using a modified n.m.r. field-gradient technique. In both polymer examples, self-diffusion coefficients were found to be proportional to M −2.0±0.1 w above and below the critical molecular weight M c. The observation of undeuterated chains in deuterated matrices of varying chain length indicates only relatively weak matrix effects. The influence of internal field gradients, which have previously been reported for polyethylene melts, is demonstrated and discussed. Certain peculiarities have been observed in the temperature dependences of the diffusion coefficients.

Self-diffusion in Zr-Cr and Zr-Fe alloys

Abstract Self-diffusion studies in a series of zirconium-rich alloys containing 2.05, 3.49, 4.08 and 7.86 at%Cr and 0.98, 1.35, 1.64, 3.54 and 6.37 at.%Fe have been carried out in the temperature range 1173–1618 K, using standard serial-sectioning technique. The temperature dependence of self-diffusion coefficients in all these alloys could be described by Arrhenius expressions of the type D = D0 exp (-Q/RT). The data have been analysed on the basis of current concepts of alloy diffusion. An analysis based on the vacancy mechanism leads to negative values of the correlation factors. The possibility of interstitial-vacancy pair and ω-phase embryos being rate-controlling mechanisms is also discussed.

Self-Diffusion in Liquids: Paraffin Hydrocarbons

The pressure dependence of the self-diffusion coefficients of several normal paraffin hydrocarbons and the isomers of hexane have been determined. In addition, the temperature dependence of self-diffusion coefficients has been measured for the isomers of hexane. Energies and volumes of activation have been calculated. With the exception of 2, 2-dimethyl butane, these parameters do not change significantly with branching in the isomers of hexane. The volumes of activation are about 10–20% of the molar volumes in all cases. Diffusion coefficients computed from a semiempirical modification of an equation derived by Longuet-Higgins and Pople are compared with the experimental results.