The present work is mostly focused on theoretical study of multiferroics and magnetic semiconductors within the framework of density functional theory (DFT). We studied Bi₂NiMnO₆ which was recently synthesized as a heavily distorted double perovskite with four formula units in a monoclinic unit cell. The calculated GGA and GGA+U magnetizations per formula unit were 4.92 and 4.99 [mu]B and the calculated ferroelectric polarizations were 16.83 and 16.63 [mu]C cm⁻². We also present the results of completely relaxed electronic structure calculations for multiferroic LaMnO₃/BaTiO₃ structure which was built by joining a slab of magnetic LaMnO₃ with a slab of ferroelectric BaTiO₃. The study of Mn doped GeTe, which is a diluted magnetic semiconductor (DMS), shows the net magnetization as a function of doping and holes concentration. In addition, we present a study of ferroelectric GeTe as a function of applied pressure and the interesting properties exhibited by Si(001)/Si(110) junction which was experimentally built using hybrid orientation technology (HOT).

No description available.

The ability to model ground-state properties in density function theory (DFT) is a ected by the theoretical treatment of the electrons and the numerical approach to the theory. The electron-electron interaction energy is approximated by exchange- correlation (XC) functionals which are functions of the electron density. Popular functionals include the localized density approximation (LDA) or one of many gen- eralized gradient approximations (GGA). The numerical approaches used are the core-electron approximating pseudopotential (PsP) or the more accurate all-electron (AE) method. We test whether PsP calculations for some new GGA's can accurately reproduce AE values for cohesive energy, lattice constant, and bulk modulus for six- teen solids. We compare our PsP results to AE results for several XC functionals and gauge the quality of functionals by comparison to experiment. This allows us to determine which errors are caused by functionals and which are caused by PsP's.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 98-106).

Thesis (Ph.D.)--Baylor University, 2007. / In abstract "n, ri1, and sj-1" are superscript. In abstract "1, k, n-k, k-1, and nk-1" are subscript. Includes bibliographical references (p. 82-84).

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 162-163). Also available on the World Wide Web.

Thesis (Ph. D. in Chemical Engineering)--Vanderbilt University, Dec. 2008. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 142-155).

Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2008. / Committee Chair: Chou, Mei-Yin; Committee Member: First,Phillip; Committee Member: Gao, Jianping; Committee Member: Landman, Uzi; Committee Member: wang, Xiao-Qian.