Graduation Year

2019

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Physics

Major Professor

Ivan I. Oleynik, Ph.D.

Committee Member

Lilia Woods, Ph.D.

Committee Member

Venkart Bhethanabotla, Ph.D.

Committee Member

Humberto Rodriguez Gutierrez, Ph.D.

Committee Member

Robert Hoy, Ph.D.

Keywords

density functional theory, equation of state, high pressure, phase diagram, phase transition

Abstract

The investigation of materials at extreme conditions of high pressure and temperature (high-PT), has been one of the greatest scientific endeavors in condensed mater physics, chemistry, astronomy, planetary, and material sciences. Being subjected to high-PT conditions, materials exhibit dramatic changes in both atomic and electronic structure resulting in an emergence of exceptionally interesting phenomena including structural and electronic phase transitions, chemical reactions, and formation of novel compounds with never-previously observed physical and chemical properties. Although new exciting experimental developments in static and dynamic compression combined with new diagnostics/characterization methods allow to uncover new processes and phenomena at high P-T conditions, there are some fundamental limitations on what can be achieved experimentally. Therefore, theory/simulations play an important role in uncovering interesting physics and chemistry of materials at much smaller cost and at much higher accuracy.

This dissertation is concerned with application of rst-principles density functional theory (DFT) to simulate and predict novel materials phenomena occurring at extreme high-PT conditions. The materials considered in this dissertation work are quite diverse and include

energetic molecular crystals, layered transition metal chalcogenides, binary Ni-Xe system, ternary H-S-O compounds, and single-element carbon, all of them being in the focus of funded research projects of my PhD advisor, Dr. Ivan Oleynik. The important results obtained in this PhD project include: (1) very accurate equation of state, properties of individual phases and phase transitions of several materials such as energetic materials and carbon, which allowed to address outstanding challenges and long-term controversies of previous experimental and simulation studies; (2) prediction of novel phases and compounds with accompanying phase transitions, such as VSe2, Sn-Se, Ni-Xe and H-S-O compounds, which will drive future experiments as well as follow up theoretical studies of these novel compounds. This work sets up new standards for high-quality theoretical prediction of physical properties of materials at extreme conditions, but most importantly, encourages experimentalists to perform more precise measurements of such properties as equation of state, phase transitions, and melting curves, as well as to attempt to synthesize newly predicted compounds with new emergent properties such as ferromagnetism or superconductivity.

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