Publication Date

Spring 2022

Document Type

Capstone Project

Degree Name

Master of Science

Department

Analytical Chemistry

First Advisor

K. G. Sanjaya Ranmohotti

Second Advisor

Joong-Won Shin

Third Advisor

Walter Henne

Abstract

The Bond Valence theory of Brown (1978) has been extensively used to correlate metal oxidation state to coordination environment in solids. Although the bond valence sum (BVS) appears to be extremely useful to coordination chemists, it has not often been applied as an alternative measure of refinement quality. In this work, previously reported six layered perovskite compounds including, RbLaNb2O7, Rb2LaNb2O7, Rb2SxLaNb2O7 (x ≤ 0.8), NaLaNb2O7, (Cs2Cl)LaNb2O7, and (FeCl)LaNb2O7, that have been prepared by topochemical manipulation and their structures have been determined by Rietveld refinements were analyzed. Our focus was to explore whether the determination of oxidation state using the bond distances derived from the Rietveld refinement method could be used to validate structure determination along with the reported goodness of fit values, χ2 , in the published structure. Good agreement between the calculated and the expected oxidation states would provide support for the chemical formula and the accuracy of a crystal structure determination.

We applied the concept of the BVS method for selective metal ions including, niobium (Nb), lanthanum (La), rubidium (Rb), sodium (Na), cesium (Cs), sulfur (S), and iron (Fe). For all these metal ions, the final values resulted from BVS calculations for the six compounds overall showed good agreement between the calculated and the expected oxidation. Although this method is empirical, it can nevertheless help us to identify important trends when a series of related and similarly prepared samples are prepared.

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