Joint diffraction and modeling approach to the structure of liquid alumina

• Published in: Physical review. B, Condensed matter and materials physics Vol. 87; no. 2
• Main Authors: Skinner, Lawrie B., Barnes, Adrian C., Salmon, Philip S., Hennet, Louis, Fischer, Henry E., Benmore, Chris J., Kohara, Shinji, Weber, J. K. Richard, Bytchkov, Aleksei, Wilding, Martin C., Parise, John B., Farmer, Thomas O., Pozdnyakova, Irina, Tumber, Sonia K., Ohara, Koji
• Format: Journal Article
• Language: English
• Published: United States American Physical Society 03-01-2013
• Subjects: Computer simulation; Condensed Matter; Diffraction; Liquids; Materials Science; Melts; Oxygen atoms; Physics; Polyhedra; Polyhedrons
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.87.024201

The structure of liquid alumina at a temperature ~2400 K near its melting point was measured using neutron and high-energy x-ray diffraction by employing containerless aerodynamic-levitation and laser-heating techniques. The measured diffraction patterns were compared to those calculated from molecular dynamics simulations using a variety of pair potentials, and the model found to be in best agreement with experiments was refined using the reverse Monte Carlo method. The resultant model shows that the melt is composed predominantly of AlO sub(4) and AlO sub(5) units, in the approximate ratio of 2:1, with only minor fractions of AlO sub(3) and AlO sub(6) units. The majority of Al-O-Al connections involve corner-sharing polyhedra (83%), although a significant minority involve edge-sharing polyhedra (16%), predominantly between AlO sub(5) and either AlO sub(5) or AlO sub(4) units. Most of the oxygen atoms (81%) are shared among three or more polyhedra, and the majority of these oxygen atoms are triply shared among one or two AlO sub(4) units and two or one AlO sub(5) units, consistent with the abundance of these polyhedra in the melt and their fairly uniform spatial distribution.