Acoustic velocities and refractive index ofSiO2glass to 57.5 GPa by Brillouin scattering

Abstract

The hypersonic sound velocity and refractive index of Si02 glass has been measured to 57.5 GPa at room temperature by Brillouin scattering in diamond cells. On compression, both longitudinal and tranverse modes exhibit an anomalous change in slope in the low-pressure region. Between 12 and 23 GPa, the sound velocities increase rapidly. At higher pressures, the bulk velocity follows a trend similar to that expected for coesite. At 57.5 GPa, the longitudinal velocity of Si02 glass is 11. 85 (+0.51) km/s and the transverse velocity is 6. 12 (+0.06) km/s. The refractive index increases monotonically with pressure and reaches a value of 1.924 (+0.081) at 57.5 GPa. It decreases reversibly on decompression to 26 GPa, but displays an irreversible change when decompressed from 16 GPa to ambient pressure. The pressure-density relation calculated from the measured sound velocities within the elastic compression region is in good agreement with several previous determinations.

Evidence of denser MgSiO3glass above 133 gigapascal (GPa) and implications for remnants of ultradense silicate melt from a deep magma ocean

“…2). Our results for SiO 2 glass along with those of previous studies (17)(18)(19)(20)(21)(22)(23)(24) indicate that the velocity-pressure trends in SiO 2 glass can be interpreted as a gradual transition from four-to sixfold coordination of Si below 40 GPa, predominantly sixfold coordination from 40 to 140 GPa, and a transition from sixfold to a higher coordination state above 140 GPa (16) (Fig. 2).…”

Size dependence of elastic mechanical properties of nanocrystalline aluminum

“…This is in good agreement with previous findings for this amorphous material. 9,[15][16][17][18]20 B. Silica glass nanowires: Surface effects When a silica NW is carved out of the bulk silica glass, the surface-to-volume ratio significantly increases, thus the surface structure will likely be different from its inner core structure and bulk counterpart, as reported recently. 10 Figure 2(a) illustrates how the radial density distribution was calculated in a NW.…”

“…As a typical disordered material, the response of bulk silica glass to mechanical loading has been demonstrated to be different from that of crystalline polymorphs both experimentally and theoretically. [15][16][17][18][19][20] Previous simulations have correlated the elastic-to-plastic mechanical response of bulk silica glass with structural transformations determined via ring size analysis, where ring size, n, is the shortest loop formed by n Si-O bonds. 19,20 The ring size distribution of bulk silica has been shown to have an average ring size of six (n ¼ 6) and the number of rings smaller and larger than this average drops off rapidly.…”

Recent Progress in High-Pressure Brillouin Scattering: Olivine and Ice.

“…Significant recent progress has been made in the coupling of Brillouin scattering and diamond anvil techniques for characterizing physical properties of materials under elevated pressures [1][2][3][4][5][6]. In some ways parallel to ultrasonic methods for measuring sound velocity and elasticity, high-pressure Brillouin scattering techniques, however, provide greater feasibility for measuring the entire set of elastic moduli for single crystals to moderate pressures.…”