The mineral prehnite, Ca2(Al,Fe,Mn)(AlSi3O10)(OH)2, is a layered structure consisting of double-sheets of (Al,Si)O4 and SiO4 tetrahedra alternating with single sheets of AlO4(OH)2 octahedra. To understand the ordering in the structure and differences between various samples of prehnite, single-crystal X-ray diffraction data at ambient conditions were collected on four single crystals of prehnite from different localities. The positions of the H atoms have been determined for the first time, from a combination of X-ray and neutron diffraction data.
The equation of state and high-pressure behavior of prehnite have been investigated using single-crystal X-ray diffraction up to 9.75(3) GPa. A second-order Birch–Murnaghan equation of state fit to the isothermal P-V data to 8.7 GPa yields a bulk modulus, K = 109.29(18) GPa. Structural data collected at high pressures indicate that the structure compresses uniformly. Above 8.7 GPa there is additional softening of the volume and the b-axis related to polyhedral tilting. However, the average structure is maintained across the transition.
Ambient and high-pressure Raman and synchrotron infrared spectra were collected from 1 bar to 20 GPa. Raman spectra measured at ambient conditions of four prehnite crystals with different compositions confirmed that there are no structural changes with different compositions. High-pressure results showed the majority of modes shift to higher frequencies (in a smooth, linear fashion) with increasing pressure. The greatest change in the spectra is the softening of the modes in the OH-stretching region above 9 GPa, thought to be related to the polyhedral tilting around the H environment. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/35702 |
| Date | 10 December 2008 |
| Creators | Detrie, Theresa A. |
| Contributors | Geosciences, Ross, Nancy L., Angel, Ross J., Ballaran, Tiziana Boffa |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | ETD_t.detrie_MSv6.pdf |
Page generated in 0.0018 seconds