GeNi2O4 is a cubic spinel with two antiferromagnetic transitions at low temperatures, while DyCrO3 has an orthorhombic perovskite structure with an antiferromagnetic transition at a higher temperature. Thin films of these compounds are widely researched for their applications in spintronics. The investigation of the structural, magnetic, dielectric, and optical properties of deposited thin films of these two materials can contribute to a better understanding of their physical characteristics which may lead to possible applications. In this research, DyCrO3 and GeNi2-xMgxO4 (x=0, 0.03) epitaxial thin films were deposited on SrTiO3 substrates using the pulsed laser deposition technique. As the c-lattice parameter of the orthorhombic DyCrO3 and a-lattice parameter of the cubic GeNi2O4 are almost having the same value, this is giving a rise to a small strain in their epitaxial thin films. Therefore, composite thin films of the DyCrO3 and GeNi2-xMgxO4 (x=0, 0.03) materials were also deposited. The structural properties of these thin films were examined using different X-ray techniques such as an X-ray diffraction, X-ray reflectivity, reciprocal space mapping, and in-plane pole figures. The results were analyzed to determine the preferred orientation, the thickness of the thin films, the presence of strain and defects, and the degree of epitaxy. The reciprocal space mapping results reveal a dependence between the thickness of the thin films and the presence of defects in the epitaxial films. The in-plane pole figure results show the presence of domains with different orientation in several thin films, although the results from the high-resolution X-ray diffraction indicate a single orientation in those films. The temperature dependence of magnetization in epitaxial thin films was measured in order to examine the magnetic anisotropy for the magnetic field normal and parallel to the surface of the films. These results indicate the presence of magnetic anisotropy in several thin films. GeNi2O4 is an interesting antiferromagnet as it has two closely spaced antiferromagnetic transitions that are the result of a spin reorientation in two types of {111} planes. Therefore, to better understand the ordering of the spins with respect to the {111} planes, additional measurements and analysis of the results were done on GeNi2O4 single crystals. The temperature dependence of magnetization was measured for the magnetic field applied parallel and perpendicular to the {111} planes. In addition, the temperature dependence of Raman spectra of a GeNi2O4 single crystal was measured and analyzed. These single crystal results of GeNi2O4 provide a better understanding of spin-phonon coupling and spin ordering and reorientation in this spinel compound.

An infrared transmission study of Ge:Mn systems is presented in this work. Various Ge:Mn samples have been prepared by both single (Mn2+ ion energy 4.76 MeV, dose 2x10^16 /cm^2) or multiple (dose 1x10^16 /cm^2) into high resistivity (100) Ge substrates. Both conventional and flash lamp annealing procedures have been used to prepare a set of samples that were characterized by X-ray Diffraction (XRD), Secondary Ion Mass Spectrometry (SIMS) and magnetometry as well as infrared transmission spectroscopy (60-8000 cm^-1). After implantation, the Ge:Mn layers are about 3 mm thick and amorphous as revealed by XRD. Samples conventionally annealed at temperatures below 250C maintained their amorphous structure. Samples annealed at temperature above 330C recrystallized into a polycrystalline structure. SIMS measurements show that the diffusion of Mn is greatly affected by the starting distribution and that diffusion is much higher in samples prepared with the lower total Mn dose. The presence of multiple magnetic phases in all the annealed samples was indicated by field and temperature dependent measurements of the total moment. Our diverse preparations suggest that the formation of secondary phases in Ge:Mn system in unavoidable. Magnetic measurements suggest that the maximum volume fraction of metallic Mn5Ge3 inclusions is of the order of 1x10^-3, much lower than the percolation threshold of metallic inclusions in an insulating matrix. Infrared transmission measurements on the same samples show the presence of a low frequency Drude like absorption with high hole concentration (p~10^ 18 /cm^3) which is greater than the critical density for metal-insulator (MI) transition in Ge. This observation suggests Mn has crystallized in substitutional sites to a far greater degree than was achieved with traditional equilibrium crystal growth. The MI transition has been investigated in the Ge:Mn system by studying the temperature dependent transmission between 4K and 300K and comparing to similar measurements on a sample of Ga-doped Ge with p = 1.5x10^16 /cm^3 which is on the insulating side of the MI transition. Finally, absorption was observed that may possibly be attributed to Mn5Ge3 inclusions in the Ge:Mn matrix.

The introductory chapters of this thesis contains an explanation to the methods and basic theory of the molecular dynamics approach. Together with the appendix section, in which a step by step tutorial how to set up and run basic simulations using the gromacs software is presented, this thesis can serve as an introductory aid in performing molecular dynamics simulations. In the research portion of this thesis, I provide several uses for the molecular dynamics approach applied to the biocide chlorhexidine as well as the study of membranes, including a mimic of the bacteria membrane of Pseudomonas Aeruginosa PA01. The motivation for this research was previous work done in our lab which determined that chlorhexidine has a high affinity for DMPC and found the depth at which it resides in a model DMPC membrane. From this information, an all-atom representation of chlorhexidine was made, which was proven to reproduce the experimental results. While we learned much about chlorhexidine in a model DMPC membrane, this study lacked the destruction of the membrane as well as the study of chlorhexidine in a biologically relevant membrane. For these reasons coarse grained versions of the all-atom chlorhexidine models as well as a new lipopolysaccharide molecule was created. With the coarse grained model of chlorhexidine and the ability to create a bacterial membrane mimic, the study of chlorhexidine and other antibacterial agents can be further studied.

The objective of pure-sampling quantum Monte Carlo is to calculate physical properties that are independent of the importance sampling function being employed in the calculation, save for the mismatch of its nodal hypersurface with that of the exact wave function. To achieve this objective, we describe a pure-sampling algorithm that combines features of forward-walking methods of pure-sampling and reptation quantum Monte Carlo. The importance sampling is performed by using a single-determinant basis set composed of Slater-type orbitals. We implement our algorithm by systematically increasing an algorithmic parameter until the properties sampled from the electron distributions converge to statistically equivalent values, extrapolated in the limit of zero time-step. In doing so, we are able to unambiguously determine the values for the ground-state fixed-node energies and one-electron properties of various molecules. These quantities are free from importance sampling bias, population control bias, time-step bias, extrapolation-model bias, and the finite-field approximation. We applied our algorithm to the ground-states of lithium hydride, water and ethylene molecules, and found excellent agreement with the accepted literature values for the energy and a variety of other properties for those systems. Some of our one-electron properties of ethylene had not been calculated before at any level of theory. In a detailed comparison, we found reptation quantum Monte Carlo, our closest competitor, to be less efficient by at least a factor of two. It requires different sets of time-steps to accurately determine the ground-state energy and one-electron properties, whereas our algorithm can achieve the same objective by using a single set of time-step values.

A new series of nano-sized Ce1-xEuxCrO3 (x = 0.0 to 1.0) with an average particle size of 50 - 80 nm were synthesized using a solution combustion method. Nano-powders Ce1-xEuxCrO3 with the canted antiferromagnetic property exhibited interesting magnetic behaviours including the reversal magnetization and the exchange bias effect. The effect of europium doping as the ion with the smaller radius size and different electron con figuration on structural, magnetic and thermal properties of Ce1-xEuxCrO3 were investigated using various experimental techniques, i.e. DC/AC magnetic susceptibility, heat capacity, thermal expansion, Raman scattering, X-ray photoemission spectroscopy, transmission/scanning electron microscopy, X-ray powder diffraction and neutron scattering. An exchange bias effect, magnetization irreversibility and AC susceptibility dispersion in these samples confirmed the existence of the spin disorder magnetic phase in Ce1-xEuxCrO3 compounds. The exchange bias phenomenon, which is assigned to the exchange coupling between glassy-like shell and canted antiferromagnetic core, showed the opposite sign in CeCrO3 and EuCrO3 at low temperatures, suggesting different exchange interactions at the interfaces in these compounds. The energy level excitation of samples were examined by an inelastic neutron scattering which was in good agreement with the heat capacity data. Neutron scattering analysis of EuCrO3 was challenging due to the large neutron absorption cross-section of europium. All diffraction patterns of Ce1-xEuxCrO3 showed the magnetic peak attributed to the antiferromagnetic Cr3+ spins while none of the diffraction patterns could detect the magnetic ordering of the rare-earth ions in these samples.

I present evidence of an antioxidant mechanism for vitamin E that correlates strongly with its physical location in a model lipid bilayer. These data address the overlooked problem of the physical distance between the vitamin's reducing hydrogen and lipid acyl chain radicals. The combined data from neutron diffraction, NMR and UV spectroscopy experiments, all suggest that reduction of reactive oxygen species and lipid radicals occurs specifically at the membrane's hydrophobic-hydrophilic interface. The latter is possible when the acyl chain adopts conformations in which they snorkel to the interface from the hydrocarbon matrix. Moreover, not all model lipids are equal in this regard, as indicated by the small differences in the vitamin's location. The present result is a clear example of the importance of lipid diversity in controlling the dynamic structural properties of biological membranes. Importantly, these results suggest that measurements of alpha-tocopherol oxidation kinetics, and its products, should be revisited by taking into consideration the physical properties of the membrane in which the vitamin resides.