Powder Diffraction Tells You What Your Material Really Is: Case Studies

Authors

Saul Henri Lapidus

Type

Text

Type

Dissertation

Advisor

Deshpande, Abhay | Stephens, Peter W | Fernandez-Serra, Maria Victoria | Dooryhee, Eric.

Date

2012-05-01

Keywords

Condensed matter physics | Powder Diffraction

Department

Department of Physics

Language

en_US

Source

This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.

Identifier

http://hdl.handle.net/11401/71310

Publisher

The Graduate School, Stony Brook University: Stony Brook, NY.

Format

application/pdf

Abstract

Powder diffraction is a useful tool for examining a number of materials that do not form single crystal for a variety of reasons. Unlike with single crystals, structure determination with powders is not a routine task. In order to demonstrate the ability and efficacy of powder diffraction and its contribution to the understanding the correlation of structures and properties, a series of compound will be presented from a wide range of types of materials: polymorphic materials, cocrystals, metal organic frameworks and magnetic materials. Each of these represent the forefront of the ability of powder diffraction, as they all introduce complications through large numbers of independent molecules and/or disorder. Two families of materials will be presented in detail, coordination polymers containing pyrazine and HF₂- and Prussian Blue analogs, that were investigated with powder diffraction. The bifluoride ion, HF₂-, contains a two-coordinate H-atom exhibiting the strongest known hydrogen bond. This was used to form materials of the form, Ni(HF₂)(pyz)₂]X (X = PF₆-, SbF₆-). These materials are quasi-1D magnets, with magnetic pathways along the biflouride ion. Two polymorphs of the PF₆- version were found and have different magnetic behavior, directly related to the structure. Additionally a number of compounds of novel and unknown composition were found and determined, Ni₂F₂(pyz)₃(H₂O)₄(BF₄)₂ and NiF(pyz)_1.5(H₂O)₂ TaF₆. Cs₂MnII[MnII(CN)₆] has the archetypal fcc Prussian blue structure, with the cations in the cubic voids. Substitution with smaller alkali ions lead to structural distortions and a marked increase in ordering temperatures. On the other hand, substitution of larger cations, NMe₄+ drives a rearrangement of the Mn-CN-Mn network and produce several previously unobserved MnII coordination geometries and a unexpected structure. | 157 pages

Recommended Citation

Lapidus, Saul Henri, "Powder Diffraction Tells You What Your Material Really Is: Case Studies" (2012). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 516.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/516