Electrical and thermal resistivities of alkali metals

The electrical and thermal resistivities of sodium, potassium and rubidium are computed in the free electron approximation using Bhatia's model of electron-lattice interaction. The normal and Umklapp contributions are obtained separately using the geometry of the reciprocal lattice. The agreement of the calculated electrical resistivity with experiment is satisfactory in the case of sodium and potassium, but not for rubidium. The general shape of the computed and experimental thermal resistivity curve is the same, but they show considerable divergence at low and high temperatures.The authors are grateful to the University Grants Commission, New Delhi, for financial aid, and to the Computer Centre, Roorkee, for providing the facilities of their IBM 1620 computer.     

Electrical resistivity of alkali metals

The temperature variations of the electrical resistivity of alkali metals lithium, sodium, potassium, rubidium and caesium are calculated in the free electron approximation and using Krebs's model for the phonon spectrum. The double average over the Fermi surface is evaluated by an improved method due toBailyn and the separation between normal and Umklapp processes is affected in a more satisfactory manner. The results of the calculations are compared with the experimental data obtained at different temperatures. The theoretical resistivity curves for sodium, potassium, rubidium and caesium show satisfactory agreement with experiment, but not in the case of lithium.     

Thermal resistivity of alkali metals

The temperature dependence of the thermal resistivity of alkali metals lithium, sodium, potassium, rubidium and caesium is determined within the free electron approximation by using Krebs's model for the phonon dispersion relations. The normal and Umklapp contributions are obtained separately from an improved method following the procedure of an earlier paper. The results of calculations are compared with available experimental information. The theoretical and experimental resistivity curves are found to be of similar nature, but they show considerable disagreement at low and high temperatures.

     

The role of high-frequency phonons in the resistivity of simple monovalent metals at liquid helium temperatures

We derive an expression for the low-temperature electrical resistivity in simple monovalent metals caused by electron-impurity and electron-phonon scattering. Since the recent measurements of the electrical resistivity of van Kempen et al. give direct evidence for the existence of phonon drag we take phonon drag into account. Our expression is exact in the limit of strong electron-impurity scattering. For the model of an acoustically isotropic metal we obtain a simple analytical formula which reproduces the experimental data on potassium fairly well, with both fitparameters, the sound velocity and the pseudopotential, being close to the values expected from other data.     

Electron-electron interactions and the electrical resistivity of lithium at low temperatures

The electron-electron interactions in lithium metal have been examined keeping in view the recent developments. The contribution of the electron-electron Umklapp scattering processes in the electrical resistivity of lithium at low temperatures has been evaluated using a simplified spherical Fermi surface model with isotropic transition probability. Our values of the electrical resistivity so obtained compare fairly well with the experimental results for lithium.      

Electron impact excitation rate coefficients for hydrogen,helium and alkali atoms

The rates of electron impact excitation of bound electronic states are calculated by interpolating the existing quantum-mechanical theories and applying an empirical correction. The calculation is done for hydrogen, helium, lithium, sodium, potassium, rubidium and cesium. The resulting rate coefficients are expressed by two parameters, the values of which are presented in tables. The error of the present calculation is estimated by comparing with available experimental data to be within a factor of approximately 2.     

Electrical properties of solid iodo mercurates resulting from the reaction of HgI2 with alcaline iodides

Potassium iodide solutions are currently used during the fabrication process of mercuric iodide based nuclear radiation detectors. However, KI treatment leaves the HgI₂ surface covered with a residual compound (namely the potassium tri-iodo mercurate) which has a significant influence on the surface properties and stability of mercuric iodide devices and therefore on the detectors characteristics. Looking for other solutions to etch mercuric iodide, we found it interesting to investigate the electrical properties of the compounds which may form when etching HgI₂ in NH₄I, NaI, and RbI. For this purpose, solid iodo mercurates with the cations ammonium, sodium, and rubidium, have been prepared by reacting HgI₂ with the solutions of interest. Study of the electrical properties of these samples and comparison with those of potassium tri-iodo mercurate ones, especially with respect to humidity, indicates noticeable stability differences in presence of water vapour. This could have interesting consequences on the surface cleaning of mercuric iodide. PACS 81.65.Cf; 81.10.Dn; 72.90.+y     

Electrical conductivity of polycrystals of nitrites of metals from the 1A group of the Periodic Table

In the process of research [1], a study was made of electrical conductivity of polycrystals of the nitrites of lithium, sodium, potassium, rubidium, and cesium, as a function of temperature from –150 °C to their melting points: 222, 438, 283, 422, and 400 ° C, respectively. The graphs of specific conductance as a function of inverse absolute temperature of the nitrites of the 1A group of the Periodic Table are broken lines whose sections characterize internal and impurity conductivities. At the points of first order phase transformations, the electrical conductivity of polycrystals of nitrites changes in jumps, as for nitrates [1]; it increases in transition from the noncentrosymmetrical to centrosymmetrical structure. Changes in ionic composition in several nitrites of the 1A group generate regular change of the parameters and of the system of crystalline lattice. The interconnection between ionic migrations in polycrystals of nitrites, energy of crystalline lattice, specific charge of ions, their radii, and energy of activation of ionic migration are shown. Polymorphic transformations in phase transitions in rubidium nitrite at –12 °C, and cesium nitrite at –98 and 80 °C, not described in the literature, were established. Polymorphic modifications of lithium, sodium, and potassium nitrites were confirmed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 7, pp. 105–108, July, 1971.     

Der Halleffekt der vier Alkalimetalle Natrium,Kalium, Rubidium und Cäsium beim Übergang vom festen in den flüssigen Zustand

The results of measurements of the Hall-effect in the alkali metals sodium, potassium, rubidium and cesium in the solid and the liquid state are communicated.     

Electrical resistivity of the alkaline earth metals Ca,Sr and Ba in the 50–300K temperature region

The computed values of the temperature dependent electrical resistivity is presented for the alkaline earth metals Ca, Sr and Ba. Numerical values of the mean free paths obtained using a finite mean free path approach is also reported. The structure factor has been evaluated using experimental values for the phonon spectra while local model potentials were used for the form factors. Our numerical results compare favourably with experiments.     

Hall-Koeffizient und elektrischer Widerstand flüssiger Al-Ga-Legierungen

The dependence of the Hall coefficient and the electrical resistivity on temperature and concentration has been measured for liquid Al-Ga alloys. The experimental Hall coefficients were found to agree with their respective free-electron values when the assumption is made that liquid Al and Ga provide 3 free electrons per atom. The electrical resistivity versus concentration is approximately a straight line and the temperature coefficient of the electrical resistivity is always positive.     

Ultraviolet-Visible Spectroscopic Investigation of Reaction of Rubidium and Tellurium in Liquid Ammonia Solution

The sequential reaction of tellurium with rubidium in liquid ammonia solution has been monitored by ultraviolet-visible spectroscopy. Reaction times for rubidium with tellurium in liquid ammonia were markedly slower than those of sodium and potassium, and the “yellow phase” intermediate was long lived and exhibited a peak at approximately 330 nm with a broad shoulder at about 440 nm. Species formed agree with those previously reported: Rb₂Te, Rb₂Te₂, and Rb₂Te₃. Rb₂Te₂ solution was a violet-blue with absorbance peaks at 285.8, 324.3, 358.0, and 560.0 nm. No evidence of disproportionation reactions for rubidium polytellurides in liquid ammonia was observed.     

A study on the correlations of supercritical temperature of fluid alkali metals based on the generalised van der Waals equation of state

The supercritical temperature, the inversion temperature and the critical compressibility factor of caesium, rubidium and potassium are correlated through the generalised van der Waals equation of state. This three-parameter equation differs from the known van der Waals equation of state by the introduction of a third parameter in the expression for molecular pressure. For caesium, rubidium and potassium, the ratios of the supercritical temperature to the inversion temperature are estimated. The results of estimation are in agreement with the results from other equations which are based on experimental data. It has been established that caesium, rubidium and potassium obey the single-parameter law of corresponding states with the ratio of the supercritical temperature to the inversion temperature as the thermodynamic similarity parameter.     

Role of the phonon trial function in determining the phonon-drag contribution to the low-temperature electrical resistivity

It is demonstrated that there is excellent agreement between the low-temperature electrical resistivity data for potassium and the Bailyn formulation for the phonon-drag electrical resistivity, which is based on a consistent solution for the phonon trial function in terms of the electron trial function.     

Effect of prior mechanical treatment on the thermal decomposition of alkali metal perchlorates

The kinetics of the thermal decomposition of sodium, potassium, rubidium and caesium perchlorates show a pronounced dependence on the past mechanical history of the materials. The variation in the decomposition rate with strain energy and lattice distortion shows that crystal defects are important factors in the thermal reactivity of alkali metal perehlorates.     

Role of polarization interaction in photoionization of negative ions of alkali metals

Photoionization processes of negative ions of sodium, potassium, and rubidium were investigated. Calculations of the dependence of the photoionization cross section on the photon energy were performed within the Random Phase Approximation with Exchange for outer subshells (RPAE) and within the Generalized Random Phase Approximation with Exchange (GRPAE) for inner subshells. The latter theoretical approach includes both many-electron correlations and core rearrangement due to escape of one of the electrons from the system. The results of calculations for the negative sodium ion were found to be in good agreement with experimental data. Better agreement was achieved by allowing dynamical polarization of the electron core. It manifests itself as a many-electron response to variation of the external electromagnetic field, which results from the excitation of the many-electron system. Detailed study of the main mechanisms determining the cross section dependence profile was carried out. These mechanisms are the inter- and intrachannel correlations acting as a many-electron response to the external field, the electron core rearrangement, and the dynamic polarization. Besides sodium and potassium ions, photoionization of rubidium ion was investigated. A new method accounting for polarization corrections to optical transition amplitudes based on combination of the Dyson equation and RPAE is proposed.     

First principles calculations of the low temperature electrical resistivity of potassium

The results of first principles calculations of the low temperature (2 K ?T?20 K) phonon-limited electrical resistivity of potassium are presented for both the Bloch limit (possible phonon drag effects are completely ignored) and the phonon drag limit (phonon-phonon collisions, which tend to suppress phonon drag, are neglected). In the former case the agreement with experiment is very good; in the latter, the calculated results are much too low. These results are at serious variance with the conclusions of Kaveh and Wiser and reopen the question of whether or not there is any evidence for important phonon drag effects in the low temperature electrical resistivity of potassium.     

Preparation and magnetic properties of zinc phthalocyanines homogeneously doped with alkaline metals

A method for preparation of homogeneous samples of metal-phthalocyanines doped with alkaline metals was developed. Polycrystalline samples of zinc phthalocyanines doped with sodium, potassium, and rubidium atoms were investigated. We measured the temperature dependence of ESR spectra of prepared samples and studied their composition and structure. It is shown that their magnetic properties depend strongly on the degree of doping as well as on the subsequent grinding and annealing.     

Density changes of bismuth and alkaline metals at the transition to the liquid state

Relative density changes δρ _f of sodium, potassium, rubidium, and bismuth on melting-crystallization were studied using monochromatic gamma-ray attenuation technique. The measurement error of density changes was 0.1–0.12 %. A comparison of the obtained results with the known literature data was carried out, and the values of δρ _f recommended as reference data were determined.     

Linear potential and electrical resistivity of liquid Na

A linear form of the ion-electron potential recently proposed by Sharma and Kachhava has been extended for the calculation of electrical resistivity of liquid sodium and for its dependence on dielectric screening. It is observed that the RBKS form of screening provides the best explanation of the electronic behaviour of liquid sodium.