Vibrational and Elastic Properties of Bulk Metallic Glass: Application to Pd64Fe16P20

Different elastic properties of Pd-based Pd64Fe16P20 have been computed using two different forms of pseudopotential. Both the forms differ within the core region suggesting different degrees of orthogonalization and its r-dependence, while outside the core both preserves the Columbic nature. The only parameter, the core radius, separates these regions, and it is calculated using the realistic assumption based on the nearest neighbor distance. Further, five different forms of the local field correlated functions, namely, Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are examined for better understanding regarding the screening effect on different elastic constants for Pd64Fe16P20 bulk metallic glass. The calculated results for the various elastic moduli, Poisson's ratio, sound velocity and phonon dispersion curve are all found to be in general agreement with the available experimental data. This confirms the applicability of the model pseudopotential to bulk metallic systems.

Elastic Properties of Zr50Cu43Ag7 Bulk Metallic Glass Using Pseudopotential Theory

Using Hubbard-Beeby approach for phonon dynamics, in conjunction with our recently proposed model pseudopotential; phonon frequencies for longitudinal and transverse modes are computed and associated elastic properties of technologically important Zr-based Zr50Cu43Ag7 bulk metallic glass (BMG) are evaluated. Five different forms of the static local field correction functions, viz., Hartree etal. (H), Taylor et al. (T), Ichimaru and Utsumi et al. (IU), Farid et al. (F) and Sarkar et al. (S) are employed to investigate the influence of the screening effect on the vibrational dynamics of Zr50Cu43Ag7 BMG. Results for bulk modulus, modulus of rigidity, Poisson's ratio, Young modulus, propagation velocity of elastic waves and dispersion curves are studied. The theoretical computations are found to be in good agreement with the available experimental results, which confirms the use of our model pseudopotential to study elastic properties of such a glassy system.

Thermal Expansion of Some Fcc Transition Metals

Volume thermal expansion of some fcc transition metals have been studied using improved lattice dynamical model. In this approach, the contribution of s like electron is calculated in 2nd order perturbation theory for the local model pseudopotential (Heine - Abrenkov) while that of the d electrons is taken into account by introduction of repulsive potential. The present study confirms that the use of improved model to study such anharmonic property yields satisfactory results. Looking to the success of present study, the present lattice mechanical model may be used to study thermophysical properties in high temperature and high pressure regions.

ELECTRICAL RESISTIVITY OF AMORPHOUS Fe AND Ni

We have calculated the electrical resistivity of amorphous transition metals Fe and Ni by using the Diffraction model as proposed by Ziman. The electron–ion interaction is described by a local model pseudopotential, and the static structure factors are taken from the experiment. The d-band effect, a characteristic of the transition metals, is accounted for through the sp–d hybridization effect. Agreement of the calculated results with the available experimental data is found to be remarkably good for both systems.

PRESSURE EFFECTS ON Mg70Zn30 SUPERCONDUCTOR

Theoretical computation of the pressure dependence of superconducting state parameters of binary Mg 70 Zn 30 is reported using model potential formalism. Explicit expressions have been derived for the volume dependence of the electron–phonon coupling strength λ and the Coulomb pseudopotential μ* considering the variation of Fermi momentum kF and Debye temperature θD with volume. The well-known Ashcroft's empty core (EMC) model pseudopotential and five different types of the local field correction functions viz. Hartree (H), Taylor (T), Ichimaru–Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) have been used for obtaining pressure dependence of transition temperature TC and the logarithmic volume derivative Φ of the effective interaction strength N0V for metallic glass. It has been observed that the μ* curve shows a linear nature and an elbow is formed in the Φ graph.