Physical Review Letters

Print Issue of December 6, 2002

Phys. Rev. Lett., 89, 245504 (2002)
URL: http://link.aps.org/abstract/PRL/v89/e245504
doi:10.1103/PhysRevLett.89.245504
PACS: 62.50.+p, 61.20.-p, 71.15.Pd, 91.60.Gf

Pressure-Induced Structural Changes in Liquid SiO₂ from Ab Initio Simulations

Andrea Trave,^1,2 Paul Tangney,^1,2,3 Sandro Scandolo,^1,2,3 Alfredo Pasquarello,^4,5 and Roberto Car¹

¹Department of Chemistry and Princeton Materials Institute, Princeton University, Princeton New Jersey 08544
²Department of Geosciences, Princeton University, Princeton New Jersey 08544
³International School for Advanced Studies (SISSA) and INFM / Democritos, National Simulation Center, I-34014 Trieste, Italy
⁴Institut de Théorie des Phénomènes Physiques (ITP), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
⁵Institut Romand de Recherche Numérique en Physique des Matériaux (IRRMA), CH-1015 Lausanne, Switzerland

First-principles molecular dynamics simulations at constant pressure have been used to investigate the mechanisms of compression of liquid SiO₂. Liquid SiO₂ is found to become denser than quartz at a pressure of about 6 GPa, in agreement with extrapolations of lower pressure experimental data. The high compressibility of the liquid is traced to medium-range changes in the topology of the atomic network. These changes consist in an increase of network connectivity caused by the pressure-induced appearance of coordination defects.