Semester

Fall

Date of Graduation

2019

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Aldo Romero

Committee Co-Chair

Mikel Holcomb

Committee Member

Edward Flagg

Committee Member

Lian Li

Committee Member

Terence Musho

Committee Member

Tudor Stanescu

Abstract

Due to increased availability and power of computational resources over the past few decades, prediction and design of novel materials using computational methods has become feasible. Simulation of material systems has become vital to the further realization of novel material systems. In order to ascertain physical properties, accurate determination and identification of stable crystalline structures is necessary. Additionally, further identification of novel properties, such as magnetic moments or orbital occupation, is necessary to further realize this goal. Global search methods provide a path to accurate prediction of these properties. In this dissertation, the Firefly algorithm and minima hopping methods are presented. The Firefly algorithm is applied to two problems: Magnetic moment orientation optimization and orbital occupation optimization. For the first, three noncollinear systems investigated: NiF2, a weak ferromagnet, and Mn3Pt and the molecular system (MnIV )3O4L4(H2O) , where L = N ,N-bis(methylene)-Z-1,2-ethenediamine, both of which display frustration. For the problem of orbital occupation, UO2 , an oxide, and KCoF3 , a perovskite-like antiferromagnet are investigated to show that FA works equally-well for d and f electron systems. The minima hopping method is applied to the problem of structural search in the binary system NiTi. The convex hull is constructed from this search. From this, results are compared to those previously reported.

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