• Synthesis of Pyrene Based Organic Semiconductors

      Youmans, Samuel; Cruse, Cody; Department of Chemistry & Physics (2017-03)
      In organic electronics, polyacenes have gained its attention to be a semiconductor due to its electronic properties. Increasing the length of the fused ring lowers the stability, therefore nitrogen atoms were introduced to the aromatic compound. In our research, synthesis of asymmetrical large pyrene-based organic semiconductor is studied.
    • Investigating the Effects of Magnetic Interaction on the Indirect Rixs Peak Location

      Stiwinter, Kenneth; Datta, Trinanjan; Department of Chemistry & Physics (2017-03)
      Resonant Inelastic X-ray scattering (RIXS) is a novel experimental technique to characterize the properties of magnetic materials. The goal of this research is to theoretically investigate the effect of spatial anisotropy and next-nearest neighbor interaction on the multiple peak location of the bimagnon RIXS spectrum. Utilizing a Green function approach within the Bethe-Salpeter scheme we wrote a python code to simulate the indirect RIXS spectrum. Using a spin wave theory magnetization phase diagram and the associated spatial anisotropy parameter (zeta) and next nearest neighbor interaction parameter (eta) we notice that the RIXS spectrum can develop multiple peaks. By fitting the location of the peaks we observe that a pattern emerges in how these peaks are affected by interaction. In the vast majority of the parameter space the peak of a fixed zeta with increasing eta combination shifts downward in frequency with each consecutive increase in eta. However, there are a couple of parameters where an upshift was observed. Based on our fits of the peak location we conclude that the pattern follows a non-linear (quadratic, cubic, or exponential) dependence on eta for a fixed zeta.
    • Thermodynamic Properties of Protein Folding Process

      Sivised, Vattika; De Silva, Theja; Department of Chemistry & Physics (2017-03)
      Proteins are one of the fundamental building blocks of life and they are present in almost all biological and cellular processes. Proteins consist of amino acids held together in a long chain by peptide bonds. When proteins function in biological processes, they fold in to three-dimensional structures by curling the chain. The folding of a peptide chain into a three dimensional structure is a thermodynamically driven process such that the chain naturally evolves to form domains of similar amino acids. The formation of this domain occurs by curling the one dimensional amino acid sequence by moving similar amino acids proximity to each other. We model this formation of domains or “ordering of amino acids” using q-state Potts model and study the thermodynamic Properties using a statistical mechanics approach. Converting the interacting amino acids into an effectively non-interacting model using a mean-field theory, we calculate the Helmholtz free energy (HFE). Then by investigating the HFE, we qualitatively study the properties of protein folding transition. We find that the protein folding phase transition is strongly first order and the specific heat shows the experimental signatures of this phase transition.
    • Studying Quantum Magnets Using Ineracting Spin Wave Theory

      Mongan, Mongan; Department of Chemistry & Physics (2017-03)
      A magnon is a quantized magnetic excitation hosted in a condensed matter state caused by deviations of the electron spin. Quantum fluctuations of the magnetic wave results in a quantized spin wave. Using spin wave theory we present a derivation of the interaction that describes magnons in a 3D ferromagnetic crystal lattice and a 2D antiferromagnetic crystal. We use both the Holstein-Primakoff and Dyson-Maleev bosonization transformation scheme. As in the literature, we find higher order interaction terms within the Hamiltonian. We present a derivation of these interaction terms and subsequent representation from a Feynman diagram approach.