Properties Of Liquid Transition Metals Research Articles

Structural properties of some liquid transition metals

This article addresses the computation of structural properties of liquid transition metals, namely, 3d (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn), 4d (Zr, Pd, Ag and Cd) and 5d (Pt, Au and Hg). We have calculated the structure factor S(q), pair distribution function g(r), interatomic distance r 1, coordination number n 1, long wavelength limit of structure factor S(0) and isothermal compressibility χT for liquid transition metals. To describe electron–ion interaction, we have used our own model potential along with one component plasma reference system. To see the influence of exchange and correlation effect, Sarkar et al.'s [Mod. Phys. Lett. B12, 639 (1998)] local field correlation function is used. Thus, our newly constructed model potential has successfully generated the structural properties (structure factor S(q), pair distribution function g(r), interatomic distance r 1, coordination number n 1, long wavelength limit of structure factor S(0) and isothermal compressibility χT ) for liquid transition metals.

Temperature-dependent structural and transport properties of liquid transition metals

The evolution of the atomic structures and diffusivity of liquid transition metals with increasing temperature has been studied here using molecular dynamics. An analysis of Honeycutt and Andersen (HA) Indices indicates that relatively low order atomic clusters of rhombohedra-related structures increase with an increase in temperature. The results illustrate that the distortion in the local structural order with a predominant rhombohedra character enhances the diffusivity in liquid metals. The excess entropy approximated by the two-body contribution increases with the distortion of the local structural order traced by the HA Indices. The relationship between the excess entropy and the reduced diffusion coefficient supports the universal scaling law proposed by M. Dzugutov. The calculated diffusivities were compared with predictions of four diffusion models. The temperature dependence of the diffusivity cannot be described by the Arrhenius Law, the moving oscillator model or the free volume model but rather by the density fluctuation model with the square proportionality of temperature.

Investigation of surface properties of liquid transition metals: Surface tension and surface entropy

In the present study, surface properties namely surface tension and surface entropy of liquid transition metals have been reported. The surface entropy of liquid Fe, Co and Ni metals has been investigated using the expression derived by Gosh et al. [R.C. Gosh, A.Z. Ziauddin Ahmed, G.M. Bhuiyan, Eur. Phys. J. B 56 (2007) 177]. To describe interionic interaction the pseudopotential approach has been used and radial distribution functions have been determined from the solution of Ornstein–Zernike integral equation. The calculated values of surface tension and surface entropy agree well with experiment. The present study shows that the expression derived by Gosh et al. leads to a good estimation for the surface entropy.

Investigation of atomic transport and surface properties of liquid transition metals using scaling laws

To test the validity of existing scaling laws which express the possible relationship between the excess entropy and transport properties, the diffusion and viscosity coefficients of liquid Fe, Co and Ni metals are calculated. To predict excess entropy, the pair distribution functions are calculated from the solution of Ornstein–Zernike integral equation. It is shown that the scaling laws proposed by Dzugutov for diffusion and by Li et al. for viscosity lead to a good estimation for diffusion and viscosity coefficients at the melting point.

Thermodynamic Properties of Liquid Transition Metals and Alloys

Thermodynamic Properties of Liquid Transition Metals and Alloys

A theoretical and computer simulation study of the static structure and thermodynamic properties of liquid transition metals using the embedded atom model

Using the Voter and Chen (VC) version of the embedded atom model, we performed molecular dynamics simulations to compute the static structure factors and some thermodynamic properties of Ni, Pd, Pt, Cu, Ag and Au in the liquid phase. The computations were carried out using both the full embedded atom model and a pair-potential approximation; both afforded quite similar results for all the metals considered. The pair-potential molecular dynamics results were in agreement with those afforded by the variational modified hypernetted chain theory using the same potentials, which confirms the accuracy of this theory for describing the static properties of liquid transition metals. Simulated and theoretical results were also compared with available experimental data, and the origin of the discrepancies observed is discussed.

Transport coefficients of liquid transition metals: A computer simulation study using the embedded atom model

Using the Voter and Chen version of the embedded atom model, we carried out molecular dynamics simulations to compute the diffusion constants and shear viscosities of liquid Pd, Pt, Cu, Ag, and Au as representative of single-particle and collective dynamic properties, respectively. The generally good agreement between the calculated values and available experimental data is evidence that the Voter and Chen embedded atom model allows a reliable description of the dynamic properties of liquid transition metals in spite of being derived from solid-state data and the properties of the diatomic molecule. The discrepancy between the reported experimental diffusion constant of liquid Cu and the values calculated in this work, together with the consistency of these latter, suggests that the reported experimental value may be in error.

Structure and thermodynamic properties of liquid transition metals: An embedded-atom-method approach.

We have obtained the volume term and effective pair potentials for liquid transition metals using the embedded-atom method (EAM). The EAM embedding functions are fitted to bulk solid-state properties: the experimental Voigt average bulk and shear moduli and sublimation energies. The same fitting procedure is used for all the transition metals. This potential is used in conjunction with the variational modified hypernetted chain (VMHNC) theory of liquids to compute the static structure factors, Helmholtz free energies, internal energies, and entropies of the 3d, 4d, and 5d liquid transition metals. There is overall good qualitative agreement with experiment. The computed thermodynamic properties exhibit trends in accordance with experiment. They also exhibit the correct behavior as a function of temperature. But the calculations also reveal shortcomings in the interatomic potential. \textcopyright{} 1996 The American Physical Society.

The electronic properties of liquid transition metals with particular reference to Fe

Abstract We have investigated the electronic structure and conductivity of liquid transition metals using parameters appropriate to Fe but, by varying the position of the Fermi energy, one can deduce the general behaviour for other transition metals. The structure (1024 atoms) is determined using molecular dynamics and an effective pair potential. The electronic properties are investigated using an s-d tight binding model in conjunction with the equation-of-motion method. We find the results are sensitive to the precise form of the hopping integrals but we obtain good agreement with experiment. The importance of this work is that it illustrates how to compute the properties of highly disordered transition metals including amorphous metals and the care that must be taken to deduce reliable results.

Calculation of Electrical Resistivity of Liquid Transition Metals

AbstractThe transport properties of liquid transition metals are discussed on the basis of Ziman's theory as generalized by Evans, Greenwood, and Lloyd. The effect of d‐band resonance in transition metals is simulated in the nearly‐free electron approximation where the ordinary (V‐matrix) pseudopotential form factor is replaced by the T‐matrix form factor in the transport integral. The T‐matrix form factor is derived in a closed form from the transition‐metal model potential V‐matrix form factor by solving the appropriate T‐matrix integral equation. The solution takes into account the deviation of the electron density of states at the Fermi level from the free‐electron value, through the ratio g = N(EF)/N0(EF), which is estimated from experimental heat capacity and McMillian's electron phonon renormalization constant in group‐B transition metals to have a mean value of order g = 2 for liquied transition metals. Based on this estimate of g and Mott's form of Ziman's formula, the electrical resistivity is calculated for all group‐B liquid transition metals using the parameters of the transition‐metal model potential obtained by Animalu in 1973. The results are in reasonable agreement with the experiment.

Thermodynamic properties of liquid transition metals

The authors present preliminary studies of the thermodynamic properties of liquid transition metals at their melting point. These have been studied by using a semi-empirical tight-binding model to describe the interatomic potential energy and with the fluid aspects modelled through a system of hard spheres optimised via the Gibbs-Bogoliubov variational scheme. Results are presented for the free energies and the equilibrium densities which exhibit trends in accordance with experiment. They have also calculated the coefficients of thermal expansion which are found to agree well with the available experimental data. The work reveals shortcomings in the model adopted for the interatomic potentials that were not evident in earlier applications to solid metals.

Application of simple model theories to thermodynamic properties of liquid transition metals

The simple one-component plasma (OCP) model has been applied to thermodynamic properties of liquid 3d transition metals. For comparison, the results calculated by the hard-sphere (HS) model are also given. The electronic contribution to the entropy and heat capacity has been considered by a rectangular model of the density of states. In spite of the simplicity of the models the calculated values of the entropy, S, the specific heat at constant volume, CV, and the compressibility chi T, are in good agreement with experiment. This indicates that the OCP model, like the HS model, is well suited as a reference liquid for liquid transition metals.

Resistivity of liquid transition metals and their alloys using the t matrix

The electrical resistivity and thermoelectric power of the liquid 3d transition metals (Ti, V, Cr, Mn, Fe, Co and Ni), Pd, Pt, Zr, Cu, Ag, Ge and Sn have been calculated using the t matrix approach and experimental structural data. Also the electrical resistivity of liquid alloys Sn-Ag, Sn-Co, Mn-Ge, Co-Ge and Mn-Cu, have been estimated in the same formulation. All the results are in good agreement with available experimental data showing that the electron transport properties of liquid transition metals and their alloys can be understood in terms of the t matrix approach.

The magnetic properties of liquid transition metals and rare earth metals

The spin susceptibility of liquid d and f band metals is studied. In particular, the author calculates for various liquid transition metal and rare earth metal alloys, the composition dependence of the spin susceptibility and of its temperature derivative. Furthermore, the change of the magnetic moment of Ce in various Ce transition metal alloys is determined.

The electrical resistivity of liquid transition metals

Abstract A discussion is given of the electrical properties of liquid transition metals and of liquid alloy systems such as Ge-Co. It is suggested that the model of Evans, Greenwood and Lloyd (1971) is valid for the latter, even for quite high concentrations of the transition metal, but that for pure liquid transition metals a different model similar to that used for crystals is appropriate, involving s—d transitions and with different mean free paths for s—p and for d electrons. In this model the resistivity does not depend much on the structure factor, so a small change of resistivity on melting and a change of [sgrave] with T such that d In[sgrave]/dT |Da 1/T is predicted. It is pointed out, however, that electron-electron collisions may make a large contribution to the resistivity and to d In σ/dT. A discussion is given of some features of the Ge-Co and Ge-Fe liquid alloys investigated by. Busch and his collaborators; it is suggested that the temperature-dependence of the resistivity may be due to a K...

Calculations of the transport properties of liquid transition metals

A simple model for electron transport in liquid transition metals, in terms of resonant scattering by a muffin-tin potential, is presented. Numerical values for the resistivity and thermopower of liquid iron and nickel are in qualitative agreement with experiment.