HR: 1330h
AN: V42A-0328    [PDF]
TI: Compressibility of Na$_2$O-2SiO$_2$ Liquid and Melt to 8 GPa Using Brillouin Scattering
AU: * Tkachev, S N
AF: Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822 United States
AU: Manghnani, M H
AF: Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822 United States
AU: Williams, Q
AF: Department of Earth Sciences, University of California, Santa Cruz, CA 95064 United States
AU: Ming, L
AF: Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822 United States
- AB: Brillouin scattering measurements have been carried out on Na$_2$O-2SiO$_2$ glass and liquid under {\it in situ} pressures to 8 GPa at temperatures from 300 K to 850 K. For the first time, the "modified" platelet scattering geometry has enabled us to determine V$_P$ independently from refractive index, and hence adiabatic compressibility and density of silicate melt as a function of pressure and temperature. In accordance with existing models for densification of silicate glasses and melts, the more compact arrangement of atoms has been assumed to account for the observed increase in density of the melt and glass phases formed at high P-T conditions. A marked change in pressure derivative of adiabatic bulk modulus (dK/dP=K$^{\prime}$) exists between the liquid (K$^{\prime}$= 6.3) and glass (K$^{\prime}$= 4.8) forms of Na$_2$O-2SiO$_2$: the notably higher K$^{\prime}$ of the liquid is consistent with the liquid being able to access a wider range of compressional mechanisms. The large K$^{\prime}$ of the liquid thus illustrates that the means of compaction of the liquid may differ substantially from that of the glass.
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3994 Instruments and techniques
DE: 3999 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting