Liquid Alloys Of Alkali Metals Research Articles

Phase behavior and atomic dynamics in RbxNa1–x: insights from machine learning interatomic potentials based on ab initio molecular dynamics

Liquid alkali metal alloys have garnered significant attention because of their potential applications in coolant systems and batteries, driven by the need for environmental conservation and technological development. However, research on these complex systems is limited, necessitating a deeper understanding to ensure their safe and effective utilization. This study presents a comprehensive investigation of the factors that determine the phase diagram of RbxNa1-x. By reproducing the experimental results using the thermodynamic integration method and machine learning interatomic potentials based onab initiomolecular dynamics simulations, we uncovered the delicate balance between the energy and entropy contributions that influence the phase stability of these liquid metal alloys. Further analysis of the liquid phase revealed the crucial roles of volume and atomic mass. Additionally, the coordination numbers of the atoms revealed distinct clustering behaviors, where Na atoms tended to avoid proximity to other Na atoms, whereas Rb atoms exhibited a strong tendency to cluster together. Moreover, the diffusion dynamics further illustrated the asymmetry in the behavior of Rb and Na, with Rb showing increased diffusion at higher concentrations and Na exhibiting higher diffusion at lower concentrations. These findings offer significant insights into the phase stability and the dynamic and structural properties of these complex liquid metal alloys.

The interdiffusion in liquid alloys of alkali metals with lead

The mutual diffusion in liquid cesium-lead alloys containing from 20 to 70 at.% Pb is investigated by a gamma-ray attenuation technique. The obtained data are compared with the results of similar studies for Li-Pb, Na-Pb, and K-Pb melts, carried out by us earlier. The concentration dependences of the interdiffusion coefficient for alkali-lead liquid systems demonstrate pronounced maxima in the vicinity of 20 or 50 at.% Pb. These phenomena confirm a tendency for chemical short-range ordering in liquid alloys.

Erratum

Erratum to the paper “The heat capacity at constant pressure in the nearly-free-electron approximation for binary liquid alloys of alkali metals” (HTHP, 2018, v. 47, p. 205-211)

Addendum to the erratum to the paper “Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys” (J. Non-Cryst. Sol., 429 (2015), p. 234)

Addendum to the erratum to the paper “Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys” (J. Non-Cryst. Sol., 429 (2015), p. 234)

A generalized model on the evaluation of entropy and entropy of mixing of liquid Na-Sn alloys

Recently proposed theory of entropy of mixing of the structurally inhomogeneous binary liquid alloys of alkali metals and group-IV elements is applied successfully to the liquid Na-Sn alloy. This alloy indicates chemical short range ordering (CSRO) i.e. exhibits partially salt like characteristics due to strong tendencies to compound formation, in the solid as well as in the liquid state. So, the generalized model for entropy of charged-hard-spheres mixture of arbitrary charge and size is employed to evaluate entropies of mixing, treating the sample as partially charge transfer system. The computed entropies of mixing are in excellent agreement with the experimental data.

Erratum to the paper “Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys” [J. Non-Cryst. Solids 401 (2014) p. 101–104

Erratum to the paper “Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys” [J. Non-Cryst. Solids 401 (2014) p. 101–104

ChemInform Abstract: Facile and Efficient Exfoliation of Inorganic Layered Materials Using Liquid Alkali Metal Alloys.

AbstractSingle‐ and few‐layer MoS2, WS2, and BN nanosheets are prepared through intercalation and exfoliation using liquid NaK or NaLi alkali metal alloys in DME at room temperature for 24—48 h.

Facile and efficient exfoliation of inorganic layered materials using liquid alkali metal alloys.

A facile and efficient exfoliation process has been reported to produce single- and few-layer nanosheets of MoS2, WS2 and BN using liquid alloys of alkali metals at room temperature. The colloidal dispersions of MoS2 and WS2 layers were highly stable over several months, which allowed us to easily prepare films of MoS2 and WS2 by vacuum filtration or spraying.

Concentration fluctuations in liquid alloys of alkali metals

Large-scale molecular dynamics simulations are performed to study the structure of liquid alloys of alkali metals (namely K–CS, Na–K, and Na–Cs) on the whole range of composition. The interactions are described by Fiolhais’ pseudopotential that has already proven its ability to describe the interactions in pure liquid alkali metals. By a comparison of the total structure factor with experimental results, the transferability of the description of the interactions is ascertained for all these systems on the whole composition range. Since these systems exhibit different behaviors at the level of the composition fluctuations, partial pair distribution functions and Bathia–Thornton’s partial structure factors are displayed for some representative compositions. The influence of the characteristics of the interactions on these fluctuations is examined. Size mismatch as well as energetic non-additivity favor heterocoordination while the attraction asymmetry encourages homocoordination. A competition between these two effects is pointed out.

Static structure of liquid alloys of alkali metals

Abstract The transferability of Fiolhais et al. (Phys. Rev. B 51 (1995) 14001; 53 (1996) 13193(E)) pseudopotential to liquid alloys is assessed. Molecular dynamics simulations are performed to predict the static structure of Na–K, Na–Cs, and K–Cs alloys at equiatomic composition. Comparison with experimental results confirms the ability of the so-called individual version of the potential to be used in the case of alloys of alkali components. The partial structure functions, experimentally unreachable, are presented and the behaviours of each system are discussed.

The Pressure of Saturated Vapors of Liquid Alloys of Alkali Metals at High Temperatures: Na–Rb System

The pressure of saturated vapors of a molten Na–Rb system is calculated from the experimental data on the activity coefficients of the components of this system at temperatures of 773 and 1073 K in a wide range of its compositions available in the literature [1, 2]. The calculated values of the saturation pressure of liquid sodium–rubidium alloys are compared with the results of an experimental investigation of the ps–Ts dependence for a Na–Rb alloy containing 60.78 at. % Rb [3].

Experimental Investigation of the Pressure of Saturated Vapors of Liquid Alloys of Alkali Metals at High Temperatures: Na–Cs System

The saturated vapor pressure of liquid potassium–cesium alloys of five compositions (15.0, 30.0, 50.0, 65.0, and 85.0 at. % Cs) is measured by the U-tube manometer method in the temperature range from 760 to 1289 K. The alloys are prepared by the weighing method at a fairly high purity of starting potassium and cesium (>99.99 wt % for each of the alkali metals). The confidential error of the experimental results is in the range from 1.0 to 1.5%. The approximating equations for the saturated vapor pressure of the investigated K–Cs alloys are derived from the statistical regression analysis of the experimental data.

Experimental Investigation of the Saturated Vapor Pressure of Liquid Alloys of Alkali Metals at High Temperatures: Na–K–Cs System

Experimental Investigation of the Saturated Vapor Pressure of Liquid Alloys of Alkali Metals at High Temperatures: Na–K–Cs System

Polyanionic clustering in crystalline and liquid alkali-group-III metal alloys

A theoretical investigation of the structural and electronic properties of crystalline and liquid alloys of alkali metals with group-III metals is presented. The results suggest the validity of a generalized Zintl principle assuming at least formally complete electron transfer, so that the local coordination and the electronic DOS in, e.g., LiGa alloys becomes Ge-, As-, and finally Se-like with increasing Li-concentration and hence an increasing number of electrons per Ga atom.

Transfer of charge in liquid alloys

Hard sphere diameters of liquid alkali metal alloys (Na-Cs and K-Rb) are calculated at 373 K ensuring the minimum Helmholtz free energy of the system. These diameters are then used to fix the packing density of the alloy. On alloying, the hard sphere diameters of Na in Na-Cs and K in K-Rb alloys expand whereas those of Cs and Rb contract.

Clustering of atoms and the metal-non-metal transition

Several liquid alloys of alkali metals (A=Li, Na, K, Rb, Cs) with group-IV (B=Si, Ge, Sn, Pb) alloys show strongly anomalous electrical transport properties for compositions AB and/or A4B. In some cases a nearly complete charge transfer leads to a nearly non-metallic behaviour (for example in Li4Sn and KPb). These anomalies are explained in terms of calculations of the electronic structure, using a tight-binding model and taking into account on-site and nearest-neighbour Coulomb interactions, clustering of B atoms and short-range order. In particular near the composition AB the presence of tetrahedral clusters B4 4- has a large influence on the properties on the liquid alloy.

Concentration Fluctuations in Liquid Alloys of Alkali Metals from Semiempirical Theories of Mixtures

The semiempirical theories of mixtures developed by van Laar, Margules, Scatchard-Hamer, Wilson and Renon and Prausnitz are used to study the concentration fluctuations of binary liquid alloys formed among the alkali metals. Examination of the fitting capabilities of these theories leads to the conclusion that those of van Laar, Scatchard-Hamer and Renon and Prausnitz are appropriate both when the atomic sizes of the component metals are similar and when there is considerable atomic size mismatch. The Margules and Wilson theories, on the contrary, appear to be restricted only to cases in which the size difference between the two types of atoms is small.

Ionic-metallic transition in gold-based liquid alkali metal alloys

The authors have calculated the density of states and conductivity of a series of gold-based liquid alkali metal alloys using a tight-binding model that includes short-range order and charge transfer in a self-consistent way. They take account of the variation of the alkali band widths, electronegativities and Coulomb interactions. The model can account for the diversity of conductivities observed at the equiatomic concentrations which range from metallic values for LiAu to ionic values for CsAu and RbAu. The calculations show that the difference of electronegativity between the alloy components is not the essential factor giving rise to the ionic to metallic transition in this series of liquid alloys, but rather it is the variations in the band widths and the interatomic Coulomb interactions that are the dominant factors.

The Electrical Properties of Gold‐Based Liquid Alkali Metal Alloys

AbstractWe present conductivity σ and partly thermopower S measurements for the liquid alkali metal‐gold alloys at the equiatomic composition. The conductivity ranges from very high values for metallic LiAu to relatively small values for ionic CsAu. The conductivity data indicate that in the liquid the transition from ionic to metallic character takes place between RbAu and KAu.

Knight shifts and Pauli susceptibilities in alkali metal alloys

Explicitly orthogonalized wavefunctions are calculated for conduction electrons at the nucleus in liquid alkali-metal alloys at all concentrations. These wavefunctions, when combined with measured alloy Knight shifts, lead to a unique Pauli susceptibility in the density range 4.0 < r s < 5.8.