| dc.identifier.uri | http://hdl.handle.net/11401/77658 | |
| dc.description.sponsorship | This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. | en_US |
| dc.format | Monograph | |
| dc.format.medium | Electronic Resource | en_US |
| dc.language.iso | en_US | |
| dc.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dc.type | Thesis | |
| dcterms.abstract | USPEX is the foremost Evolutionary Algorithm which calculates crystal structure through genetic algorithm. And it is using ab initio determination to contribute powerful searching in crystal structure prediction. This method enables crystal structure prediction at arbitrary P-T conditions, given just the chemical composition of the material. USPEX is interfaced with DFT or classic codes, such as VASP, SIESTA, GULP and so on. USPEX can also be used to search for materials with desired physical properties. There are already significant discoveries found by using USPEX. For instance, it has been found the 40-atom cell of MgSiO<sub>3</sub> post-perovskite for this fixed composition system. And for variable composition, like Mg-O system, the previous work showed that new oxides MgO<sub>2</sub> and Mg<sub>3</sub>O<sub>2</sub> could become stable at high pressure. In the crust, oxygen and aluminum have the first and third highest abundance among all elements, respectively. Also aluminum is the most abundant metal element, which takes 7.57% of the total mass of crust. Until now, there are more than 270 kinds of minerals were found containing aluminum. Aluminum is a good conductor of electricity and heat, while alumina is an insulator. But alumina is suitable for abrasive materials and cutting tools. Activated alumina could also be used as catalysts, adsorbents, dehydrating agent and a catalyst carrier. Accordingly, Al-O system is important and prospective for scientists to explore for further oxides and their properties. Materials under pressure often exhibit exotic physical and chemical behaviors. In particular, extremely new stable compounds could appear. For Al-O system, we use the variable composition searching by USPEX and have found two extraordinary compounds Al<sub>4</sub>O<sub>7</sub> and AlO<sub>2</sub> are thermodynamically stable. Al<sub>4</sub>O<sub>7</sub> is stable under the pressures between 330-443 GPa and AlO<sub>2</sub> becomes stable from 322 GPa. Detailed chemical bonding analysis shows Al<sub>4</sub>O<sub>7</sub> has one peroxide ion [O-O] <super>2− </super> in each lattice. And in AlO<sub>2</sub>, there are two peroxide bonds with different directions per lattice. As a result, under high pressure, the new state of aluminum oxides is generated with both oxygen and peroxide ions. And these two new Al-O compounds become stable because the formation of peroxide anions [O-O] <super>2-</super>. Our calculations of structure optimization and phonon spectrum also indicate the Al<sub>4</sub>O<sub>7</sub> and AlO<sub>2</sub> are stable under certain pressure. The band structures of these two aluminum oxides suggest they are both insulators. According the calculation of density of states, as we expected, most valence electrons are on oxygen atoms and rather than on Al. Also oxide and peroxide ions have different effects on the generation of conduction band.  | |
| dcterms.available | 2017-09-20T16:53:13Z | |
| dcterms.contributor | Oganov, Artem R | en_US |
| dcterms.contributor | Parise, John. | en_US |
| dcterms.contributor | Phillips, Brian | en_US |
| dcterms.creator | Liu, Yue | |
| dcterms.dateAccepted | 2017-09-20T16:53:13Z | |
| dcterms.dateSubmitted | 2017-09-20T16:53:13Z | |
| dcterms.description | Department of Geosciences. | en_US |
| dcterms.extent | 45 pg. | en_US |
| dcterms.format | Application/PDF | en_US |
| dcterms.format | Monograph | |
| dcterms.identifier | http://hdl.handle.net/11401/77658 | |
| dcterms.issued | 2013-12-01 | |
| dcterms.language | en_US | |
| dcterms.provenance | Made available in DSpace on 2017-09-20T16:53:13Z (GMT). No. of bitstreams: 1
Liu_grad.sunysb_0771M_11710.pdf: 1918108 bytes, checksum: 3aa13ddfcf3d6871eb604bf92d837389 (MD5)
Previous issue date: 1 | en |
| dcterms.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dcterms.subject | Condensed matter physics | |
| dcterms.title | Crystal Structure Prediction of Compounds in the Al-O System: AlO2 and Al4O7 | |
| dcterms.type | Thesis | |
