Interionic pair potentials and partial structure factors of compound-forming quaternary NaSn liquid alloy: First principle approach

In this paper formulae for partial structure factors have been used to study partial structure factors of compound-forming quaternary liquid alloys by considering Hoshino’s m-component hard-sphere mixture, which is based on Percus-Yevic equation of Hiroike. Formulae are applied to NaSn (Na, Sn, NaSn, Na₃Sn) which is considered as a quaternary liquid mixture with the formation of two compounds simultaneously. We have compared the total structure factors for ternary and quaternary alloys with experimental total structure factors which are found to be in good agreement. This suggests that, for suitable stoichiometric composition, two compounds are formed simultaneously. The hard-sphere diameters needed have been calculated using Troullier and Martins ab-initio pseudopotentials.      

Resistivity and thermoelectric power of molten aluminium: experiment and theory

The electrical resistivity?ρ?of metallic liquid aluminium is measured as a function of temperature. The measurement needs an experimental design able to get the resistivity of a very reactive liquid metal. Liquid aluminium seems to be a simple metal. We first interpret the experimental results by using an ab initio calculation of the electrical resistivity ρ(E) as function of the electron energy, taking into account recent exchange and correlation contributions in the framework of the generalized gradient approximation (GGA). But surprisingly the classical theoretical interpretation leads to an apparent inconsistency. Thus we discuss the sensitivity of the calculation on the inputs and propose improvements of the theoretical approach. They allow a better physical understanding of pure liquid aluminium which is absolutely necessary before undertaking the study of liquid aluminium alloys.     

Electrical resistivity of liquid binary and ternary alloys

New method of calculation of the electrical resistivity of liquid and amorphous alloys is presented. The method is based on the Morgan–Howson–S̆aub (MHS̆) model but the pseudopotentials are replaced by the scattering matrix operators. The Fermi energy is properly determined by the accurate values of the phase shifts. The model depends on a very small number of universal parameters and gives stable results. The calculated values of the resistivity agree well with available experimental data for a substantial number of binary alloys. Moreover, the results for some ternary alloys were also obtained.     

Electrical resistivity of ZnSb and CdSb liquid alloys in the compound-forming concentration range

The electrical resistivities ? and their temperature dependences $\text{d}\text{?}\text{dT}$ of liquid ZSb and CSb alloys have been determined experimentally between 40 and 52 at% Sb, corresponding to the compound-forming range. The resistivity isotherms of the two systems show one maximum at about 47 at% Sb. The electrical behaviour of the melts is related to the tendency towards compound formation.     

Electrical resistivity of liquid gold-silicon alloys

The electrical resistivity of liquid Au_1?xSi_x alloys was measured in the gold-rich concentration range, 0.16 ? x ? 0.40, as a function of temperature and composition. In this region the temperature coefficients of the resistivity is negative. The resistivities and temperature coefficients are compared with recent data on amorphous sputtered films; for x ? 0.31 the resistivities of the films are in agreement with those of the liquids within the accuracy of the measurements. The results can be interpreted in terms of the Ziman theory.     

The d-resonance scattering in amorphous Fe x Pd80−x Si20 alloy

The electrical resistivity of amorphous Fe _x Pd_80–x Si₂₀ alloy has been discussed in terms of extended Ziman theory. The increase in the electrical resistivity of Fe _x Pd_80–x Si₂₀ has been predicted due to the d-resonance scattering of the conduction electrons by Fe-atoms.Dedicated to Academician Vladimír Hajko on the occasion of his 65th birthday.     

Investigation of inter-molecular hydrogen bonding in the binary mixture (acetone + water) by concentration dependent Raman study and ab initio calculations

This paper reports that vibrational spectroscopic analysis on hydrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6-311+G(d,p) basis set. Changes in wavenumber position and linewidth (fullwidth at half maximum) have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.     

Electrical and thermal conductivities and Seebeck coefficient of liquid copper–bismuth alloys

The electrical resistivity and absolute thermoelectric power of the liquid Cu _x –Bi_{(1? x )} system have been measured over the whole composition range from the liquidus to 1100°C. The thermal conductivity is deduced from measurements of these two properties. The experimental results are interpreted and discussed in term of the extended Faber–Ziman formula using the t-matrix formalism with hard-sphere structure factors. The concentration and energy dependence of the phase shifts have been taken into account for a complete conductivity and thermopower calculation.     

Application of a structure factor-potential relationship to the electrical resistivity of the liquid alkali metals

In the Ziman formulation for the electrical properties of liquid metals, the resistivity depends on an average of the product of the structure factor and the pseudopotential. Ascarelli, Harrison and Paskin have derived a relationship for small wave vector between the structure factor and the pseudopotential for liquid metals such as the alkali metals. This formulation has been used over the entire range of wave vector (k = 0 to 2k _F). The resistivities of Na, K, Rb and Cs calculated with no adjustable parameters are within 25% of the observed values, while Li is underestimated by about a factor of five. The temperature dependencies of all but Li (which is anomalously non-linear) are in similar agreement with experiments made at constant volume.     

Theory of the residual electrical resistivity of binary actinide alloys

A system of self-consistent equations has been proposed for the coherent potential approximation of the multiband conductivity model for the case of conduction electron scattering from chaotic electric fields of ions of disordered binary alloy components at zero temperature. It has been qualitatively demonstrated that the deviation of the concentration dependence of the residual electrical resistivity of actinide alloys with multiband conductivity from the Nordheim rule is caused by the explicit dependence of the electrical resistivity of the alloy on the magnitude and sign of the real part of the Green’s function at the Fermi level. The derived system of equations for the multiband coherent potential approximation has been used to calculate the concentration dependence of the density of states and the residual electrical resistivity of the alloys of neptunium and plutonium. The results of the calculations have been compared with the available experimental data.     

Calculation of the electrical resistivity of amorphous Sn-noble metal alloys

The absolute value and temperature dependence of the electrical resistivity of amorphous AuSn and CuSn alloys have been calculated on the basis of the generalized Faber-Ziman theory. The partial structure factors of the amorphous AuSn alloys were calculated for a modified microcrystallite model using the electron diffraction data for the average structure factor. The experimentally observed difference of the temperature dependence of the resistivity in the AuSn and the CuSn series is found to be largely due to the different atomic pseudopotentials for the noble metal component in these alloys.     

Electrical resistivity of liquid Bi–Sb alloys

The electrical resistivities of liquid Bi–Sb alloys have been measured by DC four-probe method within Bi-rich composition through a wide temperature range. The distinct anomaly of a hump shape was observed on resistivity–temperature (ρndash;T) curves for liquid Bi–Sb alloys on heating at the relatively high temperatures. These anomalies have revealed the temperature-induced liquid–liquid phase transition in Bi–Sb melts. The DSC results for BiSb20wt% alloy further prove the existence of liquid–liquid transition. Measuring the ρ–T curves first on heating and then on cooling we have found that on cooling the ρ–T curve remained linear. It means that the postulated liquid–liquid transition may be irreversible.     

Temperature and concentration dependences of the electrical resistivity for alloys of plutonium with americium under normal conditions

The temperature and concentration dependences of the electrical resistivity for alloys of americium with plutonium are analyzed in terms of the multiband conductivity model for binary disordered substitution-type alloys. For the case of high temperatures (T > Θ_D, Θ_D is the Debye temperature), a system of self-consistent equations of the coherent potential approximation has been derived for the scattering of conduction electrons by impurities and phonons without any constraints on the interaction intensity. The definitions of the shift and broadening operator for a single-electron level are used to show qualitatively and quantitatively that the pattern of the temperature dependence of the electrical resistivity for alloys is determined by the balance between the coherent and incoherent contributions to the electron-phonon scattering and that the interference conduction electron scattering mechanism can be the main cause of the negative temperature coefficient of resistivity observed in some alloys involving actinides. It is shown that the great values of the observed resistivity may be attributable to interband transitions of charge carriers and renormalization of their effective mass through strong s-d band hybridization. The concentration and temperature dependences of the resistivity for alloys of plutonium and americium calculated in terms of the derived conductivity model are compared with the available experimental data.     

Electrical resistivity of liquid Ag-Au alloy

Calculations of the dependence of the electrical resistivity in liquid Ag-Au binary alloy on composition are reported. The structure of the binary alloy is described as a hard-sphere system. A one-parameter local pseudo-potential which incorporates s-d hybridization effects phenomenologically, is employed in the resistivity calculation. A reasonable agreement with experimental trend is observed.     

Free volume dependence of the electrical resistivity of metallic glasses prepared with different quenching rates

Measurements of the electrical resistivity ρ and its temperature coefficient α have been performed on amorphous ribbons prepared with different quenching rates. The variation of ρ and α with the degree of free volume frozen in these alloys is interpreted in terms of a theory based on the Ziman approach to the resistivity of metallic glasses.     

Ordering potential: the anomalous structure and properties of liquid KPb alloy

The anomalous structure and related properties of liquid KPb alloy are presented through an ab initio evaluated ordering potential as a function of concentration. It appears that considerable ordering occurs and it maximizes at the stoichiometric composition (c_k∼0.5). We then use the model to obtain the Bhatia-Thornton(BT) structure factors at different compositions (c_k=0.1,0.3,0.5 and 0.8). The calculations of concentration fluctuation and other related thermodynamic properties show that this ordering potential approach works reasonably for this compound forming liquid alloy.     

Temperature dependence of the electrical resistivity of amorphous Co80−xErxB20 alloys

The temperature dependence of the electrical resistivity of amorphous Co_80−xEr_xB₂₀ alloys with x=0, 3.9, 7.5 and 8.6 prepared by melt spinning in pure argon atmosphere was studied. All amorphous alloys investigated here are found to exhibit a resistivity minimum at low temperature. The electrical resistivity exhibits logarithmic temperature dependence below the temperature of resistivity minimum T_min. In addition, the resistivity shows quadratic temperature behavior in the interval T_min<T<77 K. At high temperature, the electrical resistivity was discussed by the extended Ziman theory. For the whole series of alloys, the composition dependence of the temperature coefficient of electrical resistivity shows a change in structural short range occurring in the composition range 8–9 at%.     

Model pseudopotentials and electronic properties of non-transition metals

Two new model pseudopotentials for electron-ion interaction in metals are proposed which contain a single adjustable parameter r_c, the radius of the ion core. The models are used in the evaluation of several properties like electrical resistivity (liquid and solid metals), thermoelectric power, electron dispersion, Fermienergy, density of states and electronic susceptibilities of certain non-transition liquid metals. The obtained results are largely satisfactory with available theoretical and experimental values. The study reveals that the present model pseudopotentials have improved in most of the cases the previous results of other one parameter models.     

Calculation of thermodynamic properties of vapor–liquid equilibria using ab initio intermolecular potential energy surfaces for dimer O2–O2

The two 5-site potentials from ab initio calculations at the theoretical level CCSD(T) with correlation consistent basis sets aug-cc-pVmZ (with m?=?4, 34) have been constructed from oxygen. The extrapolation ab initio energies were approximated by the basis sets aug-cc-pVmZ (m?=?3, 4). These two potentials were constructed by using the ab initio intermolecular energy values and a non-linear least-squares fitting method. The second virial coefficients of oxygen were determined to demonstrate the accuracy of these ab initio 5-site potentials. These ab initio potentials were employed to estimate the thermodynamic properties of the vapor–liquid equilibria by GEMC simulation. The influence of ab initio potential alone and plus 3-body interaction Axilrod-Teller potential was investigated within GEMC simulation from 80?K to 140?K. The discrepancy between them is insignificant. This showed that the two 2-body 5-site potential functions can also be used together with the 3-body interaction Axilrod-Teller potential to generate the accurate thermodynamic properties of the liquid–vapor equilibria.     

快速凝固Cu-Sn亚包晶合金的电阻率及力学性能

定量表征了快速凝固Cu-xwt%Sn(x=7, 13.5, 20)亚包晶合金的电阻率和力学性能，理论分析了冷却速率与合金性能之间的关系. 研究结果表明，在急冷快速凝固条件下，随着冷却速率的增大，合金组织显著细化、晶界增多，对自由电子的散射作用增强，Cu-Sn亚包晶合金的电阻率升高. 当晶界散射系数取r=0.992时，可用M-S模型分析其电阻率.同时，细晶强化作用增强，合金的显微硬度和抗拉强度呈线性增大，并且细晶区显微硬度略大于粗晶区显微硬度. 冷却速率的增大使合金的伸长率减小，其值在1.0%—4.6%范围.