Abstract by Megan Asplund
Chemistry and Biochemistry
Configurational Entropy of Mixing of Cobalt Iron Oxides and Manganese Iron Oxides
Cobalt iron oxides and manganese iron oxides take on a distinctive orientation of atoms known as a spinel structure. The thermodynamic properties of spinel structures have been studied, but recent experimentation suggests excess entropy of mixing for these substances. We hypothesize that although configurational entropy plays a significant role, vibrational and magnetic factors must be taken into account in order to achieve the total observed entropy change.
To test our hypothesis and deconvolute all the contributions to the entropy of mixing, a precise measure of the configurational entropy of mixing, and therefore of the structure, is necessary. Although an approximation of the structure of the materials is known, an accurate rendering obtained through polycrystalline x-ray diffraction and Rietveld refinement is necessary in order to determine exactly how much vibrational and magnetic effects contribute to the entropy of mixing.