Undergraduate Honors Theses

Thesis Defended

Spring 2015

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Geological Sciences

First Advisor

Joseph Smyth

Abstract

Schreibersite is an iron-nickel phosphide mineral (Fe,Ni)3P and is found in many iron and stony meteorites. Due to its abundance in meteorites and the inclusion of phosphorus it its crystal structure, schreibersite has significant implications for life on Earth. Schreibersite has a tetragonal crystal structure, crystalizing with the I-4 space group. This space group is non-centrosymmetric, allowing for two different crystal structures that are related to one another by an inversion symmetry operation, termed the “normal” and “inverse” structures. In previous studies, only one atomic arrangement was observed and all crystal structure refinements were based off that one structure. This means the less commonly observed crystal structure has not been as well refined. Crystal structure atom positions, occupancy and displacement parameters were refined from single crystals and were based on X-ray diffraction data using 2500 to 8000 individual intensity refinements. Four crystals were tested from the Seymchan iron meteorite, and one crystal from the Campo del Cielo meteorite. Three crystals, two from Seymchan and the one from Campo del Cielo, had the inverted crystal structure. The remaining two crystals from Seymchan possessed the normal atomic arrangement. More accurate crystal structure refinements were obtained for the normal crystal structure because of its abundance in the samples. It appears that the two enantiomorphic forms are equally and randomly distributed among the natural crystals measured.

Included in

Geology Commons

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