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Full-Text Articles in Engineering Science and Materials

Study Of Thermoelectric And Lattice Dynamics Properties Of 2d Layered Mx (M = Sn, Pb; X = S, Se, Te) And Zrs2 Compounds Using First-Principles Approach, Abhiyan Pandit Aug 2022

Study Of Thermoelectric And Lattice Dynamics Properties Of 2d Layered Mx (M = Sn, Pb; X = S, Se, Te) And Zrs2 Compounds Using First-Principles Approach, Abhiyan Pandit

Graduate Theses and Dissertations

The aim of this dissertation is the investigation of thermoelectric and lattice dynamics properties of two-dimensional (2D) MX (M = Sn, Pb; X = S, Se, Te) and ZrS2 compounds based on the first-principles density functional theory. The dimensionality reduction (e.g., using 2D structure) of bulk materials is found to have enhanced thermoelectric efficiency. This enhancement is attributed to the increase of the Seebeck coefficient as a result of higher electronic density of states near the Fermi level in low-dimensional materials. In addition, lowering the dimensionality increases phonon scattering near interfaces and surfaces in 2D materials, which leads to a …


Crystal Growth And Property Tuning Of Layered Magnetic Topological Semimetals, Krishna Pandey May 2022

Crystal Growth And Property Tuning Of Layered Magnetic Topological Semimetals, Krishna Pandey

Graduate Theses and Dissertations

The demand for energy-efficient devices has been growing rapidly due to the need for data-driven technologies and the global energy crisis. As device size approaches the atomic scale, the miniaturization of electronic devices may stop in the near future unless fundamentally new materials or device concepts are developed. The emergent topological materials with exotic properties show remarkable robustness against crystal lattice defects, which are promising for next-generation technology. These materials host exotic properties such as high mobility, large magnetoresistance, chiral anomaly, and surface Fermi arcs, etc. Among various topological materials, the ZrSiS-family materials exhibit two types of Dirac states, which …


Study Of Static And Dynamical Properties Of Complex Antiferroelectrics Materials, Kinnary Yogeshbhai Patel May 2021

Study Of Static And Dynamical Properties Of Complex Antiferroelectrics Materials, Kinnary Yogeshbhai Patel

Graduate Theses and Dissertations

The aim of this dissertation is the investigation of the static and dynamical properties of the complex antiferroelectric materials using Effective Hamiltonian method and First principles calculations. In chapter 3, a novel elemental interatomic coupling in perovskite materials which bilinearly couples the antiferroelectric displacements of cations with the rotations of the oxygen octahedra. This new coupling explains a very complex crystal structure of prototypical antiferroelectric PbZrO3. My explanation provides a unified description of many other complex antipolar crystal structures in variety of perovskite materials, including the occurrence of incommensurate phases in some of them. In chapter 4, results and analysis …


Dynamical Properties Of Ferroelectric Perovskites (Ba,Sr)Tio3 And Pb(Zr,Ti)O3 Systems From First Principles, Jeevaka Weerasinghe Aug 2012

Dynamical Properties Of Ferroelectric Perovskites (Ba,Sr)Tio3 And Pb(Zr,Ti)O3 Systems From First Principles, Jeevaka Weerasinghe

Graduate Theses and Dissertations

A first-principles-based effective Hamiltonian scheme which incorporates coupling between ferroelectric (FE) and antiferrodistortive (AFD) motions is applied to Pb(Zr,Ti)O3 alloys. It validates the existence of two modes of E symmetry (rather than the single E(1TO) soft mode) in the 50-75 cm-1 range for temperatures smaller than 200 K and for compositions falling within the Rhombohedral R3c phase. Coupling between long-range-ordered FE and AFD motions is shown to be the cause of the additional mode and more insight into its nature is provided. This scheme is further used to reveal a field-induced anticrossing involving FE and AFD degrees of …