Study of Electronic Structure, Optical and Magnetic Response of Disordered Solids
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My Ph.D program includes the theoretical studies of the electronic structure, optical and magnetic response of ordered compounds and disordered alloys. We have studied the optical conductivity and dielectric response of disordered, bulk NixPt1−x alloys and disordered, two dimensional SixC1−x. This study is based on the density functional theory (DFT) approximation and the tight binding linear muffin tin orbitals (TB-LMTO) method. Disorder is taken into account by the “Augmented Space Formalism” which allows us to accurately estimate the effect of disorder both homogeneous disorder as well as inhomogeneous disorder related to short-ranged ordering, clustering and segregation. This can be done both in bulk, surfaces and interfaces. We have overcome the defeciency of the local density approximation (LDA) and incorporated the vLB-corrected exchange correlations. Our estimation reasonably, successfully agrees with the initial experimental observations. This encourages me to go forward in this area. The proposed formalism opens up a facile way to band-gap engineer material for optoelectronic application. In parallel, we have generated the electronic structure of disordered Graphene and Graphinic materials with random vacancies and random doping have also been investigated. We have shown how the topology of the Dirac dispersion changes with disorder. We have studied disorder induced lifetime effects in 2D materials. Our study will provide a reference and detailed useful insight for building interesting nano materials. Specifically, I have worked on the magnetization dynamics and excitation spectra of disordered binary FexCo1−x alloys. We have studied the magnon softening for chemically disordered Fe20Co80 alloys in the linear spin wave regime. Our proposed formalism on magnetic response can be extended to study the spin transport, magnetic properties, excitation spectra and spin dynamics of real complex materials, ferromagnetic semiconductors and Heisenberg spin chains in disordered alloys. In this thesis, we have not only been able to study the electronic structure and response function of a few disordered systems but also successfully analyzed and interpreted the experimental results based on our theories.
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Optics, Physical Sciences, Physics