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Martin, Richard M. Mattson, William David 2015-09-25T20:02:46Z 2015-09-25T20:02:46Z 10000-01-01 2003 2003 "I report ab initio simulations of nitrogen as a function of temperature and pressure that reveal new structures and basic features of the phase diagram. In particular, the simulations show there are many structures with competitive ground state energies at the volumes that a non-molecular phase is predicted. This most favorable new structure consists of hexagonally packed zig-zag metallic chains. I show several structures to be very stable, implying large barriers to transitions. Furthermore, if there are competing structures with large barriers, it is possible for nitrogen to be transformed by pressure and temperature to an amorphous glassy structure. I investigate such amorphous glassy structures and find them to have similarities with the experimental data. I suggest a way to passivate defects in our amorphous structure leading to increased range of metastability, even to zero pressure at low T. I find characteristics of both the cubic gauche and hexagonally packed chain structure in the amorphous structure, and conclude that the experimental structure may be an amorphous collection of small clusters of these two structures. I have also carried out simulations as a function temperature that, in addition to qualitatively reproducing the experimental principle Hugoniot, predict the anomalous behavior of nitrogen under shock wave conditions, including ""double-shock-induced cooling"". I show quenching from these high temperature phases also reveals the tendency toward structures including chains and cubic-gauche-like bonding." Made available in DSpace on 2015-09-25T20:02:46Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 3101918.pdf: 5958468 bytes, checksum: 3ba384ee5c72a8e1842a70e41b5c83bd (MD5) Previous issue date: 2003 Embargo set by: Seth Robbins for item 81778 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs U of I Only 108 p. Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2003. http://hdl.handle.net/2142/80496 (MiAaPQ)AAI3101918 eng Physics, Condensed Matter The Complex Behavior of Nitrogen Under Pressure: Ab Initio Simulation of the Properties of Structures and Shock Waves text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.