Department of Theoretical Physics
http://repository.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/85
Mon, 26 Oct 2020 19:28:48 GMT2020-10-26T19:28:48ZStudy of the Bulk Properties of Liquid Transition Metals
http://repository.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/969
Study of the Bulk Properties of Liquid Transition Metals
Molla, Mohammad Riazuddin
Due to versatile applications of transition metals it is always interesting to study the properties of these metals and their alloys theoretically. The properties of transition metals largely depend on the electronic configuration of the outermost shell or nextto- outer most shell. We have studied some static and dynamic properties for liquid transition metals by using the orbital free ab initio molecular dynamics (OF-AIMD) simulation technique at thermodynamic states near their respective melting temperatures. The systems studied are the 3d (Cr, Mn, Fe, Co, Ni, Zn), 4d ( Pd, Cd) and 5d (Pt, Hg) liquid transition metals. Due to the availability of experimental data for static structure factor we have also performed simulation at several thermodynamic states for some systems, namely for liquid Fe (l-Fe), l-Zn, l-Hg, and l-Co. The OF-AIMD simulation technique is related to the density functional theory (DFT) of Hohenberg and Kohn. The exchange correlation energy is described by the local density approximation. To describe electron-ion interaction, we have used a model local pseudopotential proposed by Bhuiyan et al., which has proven to be the successful to generate the structural and dynamical properties of some liquid transition metals. The calculated results are presented here for a range of static structural magnitudes, such as static structure factor, isothermal compressibility, pair distribution function and coordination number. A comparison with the available X-ray and neutron diffraction data shows that the OF-AIMD method can provide a reasonable description of the static structure. As for the dynamic properties, results are reported for both single and collective dynamics. The calculated dynamic structure factors show side peaks which point to the existence of collective density excitations, from where the adiabatic sound velocities are calculated. Finally, we have performed calculation of some transport coefficients and obtained results are compared with the corresponding experimental data. Calculated results for static and dynamic properties are found to be good in agreement with available experimental data. We also have observed through the present work that a heavy computational demand of Kohn-Sham orbital representation of DFT used in AIMD can be partly overcomed by the OF-AIMD simulation method.
This dissertation submitted for the partial fulfillment of the requirements for the Degree of Doctor of Philosophy in the subject of Theoretical Physics.
Mon, 20 May 2019 00:00:00 GMThttp://repository.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/9692019-05-20T00:00:00ZThermodynamic and transport properties of aluminium (Al)-based liquid binary alloys
http://repository.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/371
Thermodynamic and transport properties of aluminium (Al)-based liquid binary alloys
Abbas, Md. Fysol Ibna
In this thesis, the thermodynamic and transport properties of Aluminum (Al)
based liquid binary alloys (Al1xXx, here X=Zn, In, Sn, Bi, Cu, and Au) are systematically
theoretically investigated. The thermodynamic properties of liquid binary
alloys which are named as the free energy (A), the energy of mixing ( A), the enthalpy
of mixing ( H) and the entropy of mixing ( S) have been studied.
Atomic transport properties (ATP) such as the coe cients of shear viscosity ( ),
the di usion coe cients (D), and the friction coe cients ( ) are theoretically calculated
for Al-based liquid binary systems. On the other hand, for electron transport
properties, I have also studied the electrical resistivity (
) and conductivity theoretically.
The
general microscopic theory (GMT) is employed to describe the inter-ionic
and electron-ion interactions of the above metals. The inter-ionic interaction and a
reference liquid are the fundamental components of this theory. For understanding
the inter-ionic interactions in the high temperature liquid state, the Bretonnet-Silbert
(BS) model has been used and extended it for simple metals (Al, In, Sn, Bi). This
model treats sp and d bands separately within the well established pseudopotential
mechanism. A liquid of hard spheres (HS) of two di erent e ective diameters and
charges is used to describe the reference system. The LWCA thermodynamic perturbative
method is used to calculate the e ective hard sphere diameter and the partial
structure factor, Sij (q).
For studying ATP, the distribution function method has been used which was
proposed by Rice-Allnatt (RA) and is very convenient for numerical calculations
due to its simple form. More importantly, the physical signi cances of each term
in the theory are very transparent for understanding various transport mechanisms
involved. Besides, studying the ETP for di erent liquid binary alloys, extended form
of Faber and Ziman (1965) formula has been employed to calculate the electrical
resistivity. Ziman's theory is based on the Nearly Free Electron (NFE) model and
predicting reasonable values for resistivity of liquid metals, and this theory has been
extended here for liquid binary systems.
In addition, I have also studied the thermodynamic and transport properties such
as the excess entropy, the shear viscosity and the di usion coe cient using the Universal
Scaling Laws (USL) proposed by Dzugutov for single system namely for Al.
Excess entropy is the main ingredient in the USL.
Results for both thermodynamic and transport properties of Aluminum (Al)
based liquid binary systems agree well with the available experimental data.
This thesis submitted for the degree of Doctor of Philosophy in The University of Dhaka.
Sun, 06 Oct 2019 00:00:00 GMThttp://repository.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/3712019-10-06T00:00:00Z