EFFECTS OF MANY BODY INTERACTIONS ON LIQUID AND SOLID SOLUTIONSTHROUGH MOLECULAR DYNAMICS AND AB-INITIO METHODS

Daniel Joseph Pope

doi:10.7273/000002449

Understanding many-body interactions are vital in understanding the complex emergent behavior of macroscopic systems. These interactions can be derived from and utilized within computational methods to study a variety of system properties that are difficult to achieve otherwise through experimental or analytical methods. This Dissertation focuses on the exploration of multi-component liquid and solid solutions by means of classical molecular dynamics and by quantum mechanical density functional theory calculations. In the first study, classical many-body interactions in a binary molecular liquid liquid solution were modeled from molecular potentials which described known experimental macroscopic behavior. These were then used to examine the resultant phase separating solution as determined through a classical MD simulation. A series of concentrations of methanol in supercritical carbon monoxide were modeled and graph network analysis was used to identify clustering characteristics and dynamics. Results of these simulations were then used to inform results from DOSY-NMR measurements. In the second study, many-body interactions, alternatively, were determined from first-principles calculations. Magnetic interactions in a solid-state system were determined using a combination of DFT and Cluster Expansion (CE) methods. The magnetic properties of this system were explored by treatment of the magnetic states as mixture of up and down magnetic moments. Using CE, a set of many-body interaction energies were calculated and used to determine the ground state crystal properties. These interaction energies also identified dimensionality properties of the magnetic system that allowed for finite temperature calculations of this quasi-1D system. In the final study, the determination of many-body interactions from first principles was expanded to incorporate both changes in chemical and magnetic configurations. Solid solution mixtures of aluminum, chromium, and iron oxides were examined using DFT and Cluster Expansion methods. Cluster Expansions were first used to determine the magnetic properties of pure eskolaite and hematite. The phase boundaries of these systems with corundum were then calculated with considerations for the configurational, vibrational, and magnetic contributions.

EFFECTS OF MANY BODY INTERACTIONS ON LIQUID AND SOLID SOLUTIONSTHROUGH MOLECULAR DYNAMICS AND AB-INITIO METHODS

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