B. Y. Thakore

Some static and vibrational properties of aluminium by a local pseudopotential

The pseudopotential investigation of various properties of aluminium is studied in terms of the real-space sum of Born-von Karman central-force constants. A simple local model potential depending on a single parameter has been used to investigate the ion-ion interaction, interatomic force constants, dynamical elastic constants, bulk modulus, deviation from Cauchy relation, Poissons ratio, Youngs modulus, propagation velocity of elastic waves, phonon dispersion curves and degree of elastic anisotropy. The effect of exchange and correlation on conduction electrons is also considered separately by using various forms of the dielectric (screening) functions. Overall good agreement with the available theoretical and experimental data is achieved in the present work.

The temperature-dependent electrical transport properties of liquid Sn using pseudopotential theory

We present the calculations of electrical resistivity, thermo-electric power and thermal conductivity based on the self-consistent approximation. The pseudopotential due to Hasegawa et al. [J. Non-Cryst. Solids 117/118, 300 (1990)] for full electron–ion interaction, which is valid for all electrons and contains the repulsive delta function to achieve the necessary s-pseudisation, was used in the calculation. Temperature dependence of structure factor is achieved through temperature-dependent potential parameter in the pair-potential. The outcome of the present study is discussed in the light of other such results and with predictions of Wiedemann and Franz law up to moderately high temperature. Specially, high-temperature resistivity data necessitates the careful investigation of electron energy dispersion close to the Fermi level and possible metal to non-metal transition while going from dense-fluid to low density-fluid state. In the absence of experimental data at high temperature, these findings may serve as future guideline.

Collective modes in Ca70Mg30 glass

The self-consistent phonon scheme given by Takeno and Goda, involving multiple scattering and phonon eigen frequencies which are expressed in terms of many-body correlation functions of atoms as well as of interatomic potential in the solids, has been used to generate the collective modes in the Ca70Mg30 glass. A model potential is proposed to describe the effective interaction in the glass. Three different forms of the local field correction functions viz. Hartree, Taylor and Ichimaru and Utsumi are used to examine relative influence of exchange and correlation effects. The phonon frequencies of the longitudinal and transverse modes are computed employing the theoretical formulation of Hubbard and Beeby. The elastic property of the glassy system is then studied using the long wavelength limits of the phonon modes. The theoretical computations reproduce much better dispersion curves (both for the longitudinal and transverse phonons) compared to earlier reports and are found to be in good agreement with the available experimental results due to neutron scattering.

Thermodynamic properties of 3C SiC

In the present paper, we report on the results of various thermodynamic properties of 3C‐SiC at high pressure and temperature using first principles calculations. We use the plane-wave pseudopotential density functional theory as implemented in Quantum ESPRESSO code for calculating various cohesive properties in ambient condition. Further, ionic motion at a finite temperature is taken into account using the quasiharmonic Debye model. The calculated thermodynamic properties, phonon dispersion curves, and phonon densities of states at different temperatures and structural phase transitions at high pressures are found to be in good agreement with experimental and other theoretical results.

Collective Modes and Elastic Constants of Liquid Al83Cu17 Binary Alloy

The collective dynamics (longitudinal and transverse phonon modes) are studied for aluminum-copper (Al-Cu) binary alloy in terms of the eigen-frequencies of the localized collective excitations. The model pseudopotential formalism is employed using a self-consistent phonon scheme by involving multiple scattering and phonon eigen-frequencies. These frequencies are expressed in terms of many-body correlation functions of atoms as well as of interatomic potential. The important ingredients in the present study are the pair-potential and pair-correlation functions. The most recent and sparingly used local field correlation functions are employed to investigate the influence of the screening effects on the vibrational dynamics of non-crystalline Al83Cu17 binary alloy. The results for the elastic constants like bulk modulus BT, rigidity modulus G, Poissons ratio ζ, Youngs modulus Y, Debye temperature θD, propagation velocity of elastic waves and dispersion curves are reported based on the collective modes of this binary alloys. The present results are consistent and confirm the applicability of model potential and self-consistent phonon theory for such studies.

Temperature dependent atomic transport properties of liquid Rb

A simple analytical model for atomic motion is used to obtain velocity autocorrelation function (VACF) for liquid Rb. The modified empty-core potential due to Hasegawa et al., which represents the orthogonalisation effect due to s-core states in such sp-bonded metals, is used for electron–ion interaction. The potential parameter rc is determined at different temperatures from the knowledge of structure factor. We find quantitative explanation for the density and temperature dependence of VACF and self-diffusion coefficients. The coherent behaviour of liquid Rb in terms of the dynamic structure factor employing viscoelastic theory has also been studied. Intrinsic temperature effects have been studied through damping term in the pair potential. The predicted results for VACF, cosine power spectrum, mean square displacement, diffusion and viscosity coefficients have been compared with recent available molecular dynamics (MD) data and a good agreement has been achieved.

The temperature dependent collective dynamics of liquid sodium

Liquid alkali metals show, near the melting point, an upward bending of the dispersion relation at small momentum transfer values. This so-called positive dispersion can be described within generalized hydrodynamics as a visco-elastic reaction of the liquid. There is a speculation that long-living clusters could be the physical reason behind this phenomenon. To shed light on this question a treatment of pseudopotential theory on liquid sodium was performed at different temperatures starting at the melting point. In the present study, we used the modified empty core potential due to Hasegawa et al. (J. Non-Cryst. Solids, 117/118 (1990) 300) along with a local field correction due to Ichimaru-Utsumi (IU) to explain electron-ion interaction. The potential used is composed of a full electron-ion interaction and a repulsive delta function, which represents the orthogonalisation effect due to the s core states. The temperature dependence of pair potential is calculated by using the damping term exp(-πkBTr/2kF)....

Asphericity in the Fermi surface of aluminium and lead

A detailed study of asphericity in the Fermi surface of aluminium (Al) and lead (Pb) along three symmetry directions [100], [110] and [111] is made on the basis of pseudopotential theory extending upto second order. The influence of exchange and correlation effects on the asphericity in the Fermi surface is examined explicitly by using four different forms of screening function. For polyvalent metals Al and Pb the distortion in the Fermi surface is found to be sensitive in regard to various local field corrections.

Study of phonon modes and elastic properties of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 rare-earth bulk metallic glasses

A phonon modes and elastic properties of two different rare-earth based bulk metallic glasses Sc36Al24Co20Y20 and Gd36Al24Co20Y20 are computed using Hubbard-Beeby approach and our well established model potential. The local field correlation functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar Sen et al (S) are employed to investigate the influence of the screening effects on the vibrational dynamics of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 bulk metallic glasses. The results for bulk modulus BT, modulus of rigidity G, Poissons ratio ξ, Youngs modulus Y, Debye temperature ΘD, propagation velocity of elastic waves and dispersion curves are reported. The computed elastic properties are found to be in good agreement with experimental and other available data.

Electrical transport properties of amorphous Ni32Pd53P15 alloy

A ternary alloy containing nickel, palladium and phosphorous in amorphous form has been studied. The electrical transport properties viz. electrical resistivity, thermoelectrical power (TEP), thermal conductivity are computed using our recently proposed potential. In the present work, five screening functions have been employed to incorporate the exchange and correlation effects. The theoretical structure factors due to hard core fluid theory have been used in the calculations. The liquid alloy is studied as a function of its composition at temperature 294 K. The partial structure factors of the compound-forming Ni32Pd53P15 ternary alloy has been calculated by considering Hoshino’s m-component hard-sphere mixture, which is based on Percus-Yevic equation of Hiroike.