|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
-AlOOH and -AlOOD at high pressure: A study of isotope effect and hydrogen-bond symmetrization
1 Department of Earth and Planetary Materials Science, Tohoku University, Sendai 980-8578, Japan
2 Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
3 Geochemical Laboratory, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
4 Department of Natural History of Sciences, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
5 National Institute for Materials Science, Tsukuba 305-0044, Japan
 |
ABSTRACT |
|---|
 Top Abstract IntroductionExperimental methodsResults and discussionAcknowledgmentsReferences cited |
|---|
-AlOOH and -AlOOD were investigated under quasi-hydrostatic conditions at pressures up to 63.5 and 34.9 GPa, respectively, using results from synchrotron X-ray diffraction experiments conducted at ambient temperature. Because of the geometric isotope effect, at ambient pressure, the a and b axes of -AlOOD, which define the plane in which the hydrogen bond lies, are longer than those of -AOOH. Under increasing pressure, the a and b axes of -AlOOH stiffen at 10 GPa, although the c axis shows no marked change. Identical behavior was found in -AlOOD, but the change in compressibility was observed at a slightly higher pressure of 12 GPa. Axial ratios a/c and b/c first decrease rapidly with increasing pressure, then begin to increase at pressures >10 GPa in -AlOOH and >12 GPa in -AlOOD. At these pressures, the pressure dependence of a/b also changes from increasing to decreasing. The unit-cell volumes of -AlOOH and -AlOOD become slightly less compressible at high pressures. Assuming K0' = 4, the calculated bulk moduli of -AlOOH below and above 10 GPa are 152(2) and 219(3) GPa, respectively. Those of -AlOOD below and above 12 GPa are 151(1) and 207(2) GPa, respectively.
Key Words: -AlOOH • -AlOOD • hydrogen bond • symmetrization • high pressure • isotope effect
|
INTRODUCTION |
|---|
|
TopAbstractIntroductionExperimental methodsResults and discussionAcknowledgmentsReferences cited |
|---|
-AlOOH, which is a high-pressure polymorph of diaspore (
-AlOOH) and boehmite (
-AlOOH) (Suzuki et al. 2000), is remarkable for its wide stability field. The stability field of -AlOOH was found to cover the pressure range from 18 to >130 GPa, and temperatures up to 2300 K, which corresponds to conditions at the bottom of the lower mantle (Ohtani et al. 2001; Sano et al. 2004, 2008). To date, no other hydrous mineral has been shown to be stable up to such high pressures. The structure of -AlOOH has been refined from powder X-ray diffraction data using the Rietveld method (Suzuki et al. 2000), and using single-crystal refinement methods (Komatsu et al. 2006). It is isostructural with InOOH (space group P21nm) and resembles distorted rutile-type (CaCl2-type) SiO2. Edge-sharing AlO6 octahedra form a single chain along the c axis; a hydrogen bond is formed in the tunnel between the chains. Raman, NMR, and powder neutron diffraction experiments were conducted to investigate the hydrogen bond in -AlOOH. Results of 1H NMR studies showed that the hydrogen in -AlOOH is highly ordered (Xue et al. 2006; Xue and Kanzaki 2007). A neutron diffraction experiment on -AlOOD at ambient pressure determined the O–D, D···O, and O···O distances as 1.02, 1.55, and 2.57 Å, respectively (Vanpeteghem et al. 2007), showing that a strong hydrogen bond is formed at ambient pressure. Therefore, this is a good system for investigation of the response of a strong hydrogen bond to pressure and the effects it has on the physical properties.
Compression of a linear O–H···O hydrogen bond results in symmetrization. This phenomenon is well studied in H2O ice (e.g., Goncharov et al. 1996; Aoki et al. 1996; Song et al. 1999; Benoit et al. 1998) and its sequence has been described as follows: The proton potential well has double minima along the O···O line, and the proton is localized in one of them in a moderate hydrogen bond at lower pressure. With increasing pressure, O···O separation decreases and the potential barrier between two minima is lowered (ice VII). The proton becomes disordered when it can overcome the barrier by tunneling motion (disordered ice VII). Further compression leads to symmetrization, in which the proton is centered between the O atoms (ice X). It is also predicted that the proton will take a unimodal distribution, due to zero-point motion (the proton is dynamically disordered in ice X), before the proton potential well becomes a completely single minimum (Benoit et al. 1998). Reports of previous theoretical and experimental studies have suggested that upon compression the hydrogen bond strengthens in -AlOOH and ultimately symmetrizes. Using first-principles calculations, Tsuchiya et al. (2002) first pointed out that a symmetric hydrogen bond is formed in -AlOOH at 28 GPa. The space group changes from P21nm to Pnnm at the symmetrization transition. Although some disagreement about the transition pressure exists, results of other theoretical studies also suggested that a symmetric hydrogen bond is formed in -AlOOH. Li et al. (2006) did not report the exact transition pressure, but calculated the electron charge density distribution showing that the hydrogen bond is asymmetric at ambient pressure, whereas it is symmetric at 50 GPa. Panero and Stixrude (2004) reported that a symmetric hydrogen bond is stable at ambient pressure, but their result conflicts with results of published experimental studies that were conducted under ambient conditions (Vanpeteghem et al. 2007).
A neutron diffraction study on deuterated -AlOOD was conducted recently at pressures up to 9.2 GPa (Sano-Furukawa et al. 2008) to examine, experimentally, the possibility of hydrogen-bond symmetrization at high pressure. The O–D···O hydrogen-bond geometry in -AlOOD was found to remain asymmetric at pressures up to 9.2 GPa. However, as pressure increases, the shorter covalent O–D bond length increases, whereas both the longer D···O hydrogen-bond length and the O···O distance decrease. The hydrogen-bond geometry at 9.2 GPa consists of an O–D bond length of 1.05 Å, a D···O bond length of 1.40 Å, and an O···O distance of 2.45 Å. The result implies that the hydrogen bond in -AlOOD is strengthened by compression and is expected eventually to become symmetric at some pressure >9.2 GPa.
The effect of the symmetrization of hydrogen bonds on the compressional behavior of minerals remains unclear, but important predictions have been made about the compressibility of -AlOOH based on results of theoretical studies. Tsuchiya et al. (2002) and Panero and Stixrude (2004) suggested that in -AlOOH, at lower pressures where the hydrogen bond is asymmetric, the a and b axes defining the plane in which the hydrogen bond lies are more compressible than the c axis. On the other hand, the a and b axes are stiffened by the symmetrization, although the c axis is unaffected. Therefore, the c axis becomes the most compressible direction at high pressure. It is also predicted that the bulk modulus increases by symmetrization (Tsuchiya et al. 2002; Tsuchiya and Tsuchiya 2009). Tsuchiya and Tsuchiya (2009) recently redetermined the bulk modulus and showed that elastic wave velocities vP and v
increase anomalously by symmetrization. However, these theoretical predictions have not yet been supported by experimental studies. Vanpeteghem et al. (2002) conducted X-ray diffraction studies on -AlOOH up to 22.5 GPa and suggested that the c axis is the most compressible direction over all of this pressure range. In contrast, a neutron diffraction experiment on -AlOOD showed that the b axis is the most compressible axis at pressures up to 9.2 GPa (Sano-Furukawa et al. 2008).
A comparative study of protonated and deuterated samples is necessary to connect the data of previous neutron diffraction studies on -AlOOD to other experimental and theoretical studies on -AlOOH because a strong hydrogen bond is known to have a considerable isotope effect. Since the symmetrization is a phenomenon related to tunneling motion and zero-point vibration, the mass effect is significant. In fact, the transition to proton-disordered ice VII in D2O is reported to occur at a pressure 10 GPa higher than that in H2O (Song et al. 1999). An isotope effect on hydrogen-bond geometry, named the geometric isotope effect 
R, exists even at ambient pressure. It is defined by the difference in the O···O distance of O–H···O and O–D···O hydrogen bonds; R = (O···O)D – (O···O)H. Ichikawa (2000) investigated O–H···O and O–D···O geometries in various materials, demonstrating that the effect of deuteration on the hydrogen bond is to expand the distance between two O atoms in a strong hydrogen bond, where the O···O distance is in the range of 2.43–2.65 Å. R reaches a maximum value around (O···O)H distances near 2.5 Å, where the mass effect on the shape of the double minimum potential well and tunneling motion is significant (Matsushita and Matsubara 1982). The O···O distance of distorted-rutile type oxyhydroxides, including -AlOOH, falls into the range where R is significant. For example, R of distorted rutile-type β-CrOOH(D) is 0.046 Å with an (O···O)H distance of 2.47 Å (Fujihara et al. 2002).
This report presents the results of compression experiments on -AlOOH and -AlOOD to 63.5 and 34.9 GPa, respectively, under quasi-hydrostatic conditions. A comparison between protonated and deuterated samples is useful to combine the data with previous neutron diffraction studies of -AlOOD and other studies on -AlOOH. Combining these results, we discuss the effect of the symmetrization of the hydrogen bond on the compressibility of -AlOOH and -AlOOD.
|
EXPERIMENTAL METHODS |
|---|
|
TopAbstractIntroductionExperimental methodsResults and discussionAcknowledgmentsReferences cited |
|---|
-AlOOH and -AlOOD were conducted using a Kawai-type high-pressure apparatus at Tohoku University. The starting materials of gibbsite [-Al(OH)3] or deuterated bayerite [β-Al(OD)3] were loaded into a platinum or gold capsule and kept at 18 GPa and 900–1000 °C for 30–60 min. Deuterated bayerite was obtained as a precipitate from a mixture of D2O and NaAlO2. The synthesized samples were confirmed as -AlOOH (or -AlOOD) using a micro-focused X-ray diffractometer, and they were ground into fine powders using an alumina mortar. The deuterated sample was identical to that used in previous neutron diffraction studies (Vanpeteghem et al. 2007; Sano-Furukawa et al. 2008). The degree of deuteration of the sample was determined as AlOO[D0.744(2)H0.256(2)] through Rietveld refinement of neutron diffraction data taken at ambient conditions. Hereafter, we refer to this composition as AlOOD.
X-ray diffraction experiment
Compression experiments were performed using a diamond anvil cell with flat culet diamond anvils having culet sizes of 350 µm for the experimental runs on -AlOOH, and 450 µm for the run on -AlOOD. A rhenium gasket with initial thickness of 250 µm was pre-indented to 60 µm in thickness. The powdered starting material was loaded into the sample hole of the gasket together with small ruby spheres. Two sets of compression experiments were performed on -AlOOH under quasi-hydrostatic conditions; one was conducted to 63.5 GPa using helium as the pressure medium; the other was performed to 63.0 GPa using neon. Each gas pressure medium was introduced into the sample chamber using a gas-loading system operating with gas pressures of 180 MPa at the National Institute for Materials Science (NIMS; Takemura et al. 2001) and of 150 MPa at the Institute for Solid State Physics (ISSP) at the University of Tokyo. The pressure was determined using the ruby-fluorescence method (Zha et al. 2000). Errors in the determined pressures of each data set are <2%.
Angle dispersive diffraction patterns were collected for -AlOOH at the BL04B2 beamline at SPring-8, and for -AlOOD at the BL13A beamline at the Photon Factory. Diffraction patterns were collected using an imaging plate (IP) for exposure times of 15–60 min. The X-ray wavelength, the distance from the sample to the IP, and pixel sizes of the IP were calibrated using the diffraction peaks of CeO2. The wavelength was 0.33091(4) Å at BL04B2, and 0.42651(4) Å at BL13A. The diffracted image was integrated into a 1D powder pattern as a function of 2
using the WinPiP software. Diffraction peaks were fitted with a pseudo-Voigt function; the 110, 011, 111, 210, 211, 121, 220, 310, 002, 130, and 112 reflections were used to calculate the lattice parameters. In some data sets, the 002, 211, and 112 reflections were excluded from the calculation of the lattice parameters when they overlapped with the diffraction peaks of the rhenium gasket and the Ne pressure medium.
|
RESULTS AND DISCUSSION |
|---|
|
TopAbstractIntroductionExperimental methodsResults and discussionAcknowledgmentsReferences cited |
|---|
and 2. At ambient conditions, the lattice constants of -AlOOD are slightly larger than those of -AlOOH: the differences in lattice constants a, b, and c of -AlOOD and -AlOOH are 0.0052(12), 0.0101(11), and 0.0015(6) Å, respectively. Previous studies have determined the O···O distance to be 2.55 Å in -AlOOH using single-crystal X-ray diffraction (Komatsu et al. 2006), and 2.57 Å in -AlOOD, by powder neutron diffraction (Vanpeteghem et al. 2007). Because the techniques used in these studies differ, a simple comparison of O···O distances could not be made, but the determined (O···O)H distances are in the range where the geometric isotope effect is significant. In the present study, the unit-cell parameters of -AlOOH and -AlOOD were obtained using X-ray powder diffraction, so a precise comparison is possible. In particular, the a and b axes are elongated by deuteration beyond experimental error. Because the hydrogen bond in -AlOOH is oriented in the a–b plane, making a smaller angle with the b axis, deuteration would have a strong effect on the length of the b and a axes, and a smaller effect on the c axis.
|
|
-AlOOH run using the helium pressure medium, the 010 and 120 reflections that were observed at 0.22 GPa disappeared at 4.83 and 6.53 GPa, respectively (Fig. 1). In the run of -AlOOD, 010 and 120 peaks were observed to 4.67 GPa, but they disappeared at 9.27 GPa. These peaks’ intensities are too weak to determine the exact pressure at which they disappeared in the present X-ray powder diffraction experiments. However, our results imply the existence of a P21nm–Pnnm transition. The 010 and 120 peaks were observed only for those measurements performed on -AlOOH using a helium pressure medium. It is likely that in the other -AlOOH runs, the peaks were not observed because of the high background from the neon pressure medium and the diamond backing plate.
|
-AlOOH(D)-AlOOH and -AlOOD with increasing pressure. The compressibilities of the normalized unit-cell parameters of -AlOOH are shown in Figure 2. The normalized axes display non-linear variations with pressure. Below 10 GPa, the most compressible direction is the b axis, and the least compressible one is the c axis, in agreement with previous neutron diffraction experiments (Sano-Furukawa et al. 2008). The evolution of the c axis could be fitted by a single curve for the pressures up to 63.5 GPa. However, the a and b axes stiffen at pressures higher than 10 GPa. The a and b axes are compressed by 2 and 2.4% from 0 to 10 GPa, respectively, but they are subsequently compressed only by a further 1.4 and 1.3% from 10 to 20 GPa (Fig. 2, inset). Consequently, the most compressible axis is c and the least compressible axis becomes b for pressures of 10–63.5 GPa. The same behaviors of the axial compressibilities were found in -AlOOD (Fig. 3), but an isotope effect influences the pressure at which compressibilities change. The pressure at which the a and b axes of -AlOOD stiffen is 12 GPa, which is slightly higher than that at which the effect takes place in -AlOOH (10 GPa). These behaviors are not caused by increasing deviatoric stress because the split of the R1–R2 ruby fluorescence line, which is a good gauge for deviatoric stress (Chai and Brown 1996), showed no significant change under these conditions. The result of the present study differs from those of a previous compression study of -AlOOH. Using a similar technique to that used in the present study, Vanpeteghem et al. (2002) found that the b axis is stiffer than the a axis, and that the c axis is the most compressible; they also found no changes in the axial compressibility. For some reason, the errors in the determination of the cell parameters in Vanpeteghem et al. (2002) were greater than those of the present study. Moreover, the data were collected with pressure steps of 2–5 GPa up to 22.5 GPa, so that the slight change observed in the present study could not have been detected.
|
|
shows that the changes in axial compressibilities are reflected in the plot of the pressure dependencies of the axial ratios b/c, a/c, and a/b. The inflection points of the pressure dependence of the axial ratios that correspond to the stiffening of the a and b axes are readily apparent in the plots. In -AlOOH, the axial ratios a/c and b/c first decrease rapidly with increasing pressure, then begin to increase at pressures above 10 GPa. The pressure dependence of a/b also reverses at 10 GPa from increasing to decreasing with increasing pressure. Because of the isotope effect, the a and b axes of -AlOOD are longer than those of -AlOOH. For that reason, at ambient pressure, b/c and a/c start from higher values in -AlOOD. The inflection point of -AlOOD is also located at a higher pressure (12 GPa) than for -AlOOH (10 GPa). The rates of change of the axial ratios of -AlOOD as a function of pressure are slightly lower than those of -AlOOH. Therefore, the discrepancies in axial ratios between -AlOOH and -AlOOD gradually increase as pressure increases below the inflection point. At 12 GPa, the axial ratios of -AlOOD reach almost identical values for those of -AlOOH. No isotope effect on the axial ratios was observed at pressures >12 GPa. Irrespective of the structural similarity, the changes in axial compressibilities and axial ratios seen in -AlOOH have not been observed in any analogous anhydrous CaCl2-type MX2 compound, indicating that the change in axial compressibility is a phenomenon related to the hydrogen bond. For example, in CaCl2-type SiO2, c/b decreases continuously, although c/a increases continuously, each with no inflection at pressures of 60–120 GPa (Andrault et al. 1998).
|
-AlOOH(D)-AlOOH and -AlOOD is presented in Figures 5 and 6. The previous experimental result is also plotted in Figure 5. The unit-cell volume determined by the experiment on -AlOOH using neon as a pressure medium yields a slightly larger value than that using helium at pressures >48 GPa, probably because of the lack of hydrostaticity of neon at high pressure (Fig. 5). The bulk moduli calculated using each data set using the helium and neon pressure media, respectively, agree within experimental precision: 190(1) and 193(2) GPa, where K0' is fixed to 4. Therefore, we will hereafter discuss the equation of state ignoring the nature of the pressure media.
|
|
-AlOOH and -AlOOD become slightly less compressible at pressures >10 and 12 GPa, respectively. The calculated bulk moduli from the Birch-Murnaghan equation of state are presented in Table 3, along with the results of previous studies. If we tentatively fit the correlation using a single equation of state over the whole pressure range of the present experiment, discrepancies were found between the calculated curve and observed data because of the inflection points around 10 GPa (Figs. 5
and 6). Fitting with separate equations of state at 10 GPa, bulk moduli of -AlOOH were determined to be 152(2) and 219(3) GPa for the pressures below and above 10 GPa, respectively, where K' is fixed to 4. In -AlOOD, the bulk moduli were determined to be 151(1) and 206(2) GPa, for the pressures below and above 12 GPa. -AlOOH is found to be more compressible in the pressure range below 10 GPa than previously reported. The bulk modulus in the lower pressure region is similar to that of diaspore (-AlOOH; 151 GPa, Friedrich et al. 2007), and almost consistent with the result of a theoretical calculation on the structure with an asymmetric hydrogen bond (Tsuchiya and Tsuchiya 2009). On the other hand, bulk moduli above 10 and 12 GPa for -AlOOH and -AlOOD, respectively, are consistent with the theoretical results on the structure with a symmetric hydrogen bond (Panero and Stixrude 2004; Tsuchiya and Tsuchiya 2009).
|
-AlOOH observed in this study implies a symmetrization of the hydrogen bond. The compression behavior of -AlOOH described in this report is in agreement with previous theoretical studies by Tsuchiya et al. (2002) and Panero and Stixrude (2004). Although some disagreement is apparent in relation to the transition pressure (28 GPa, Tsuchiya et al. 2002; –8 GPa, Panero and Stixrude 2004), both reports described that the a and b axes are stiffened by symmetrization of the hydrogen bond. The increase in bulk modulus was observed in agreement with the results of theoretical studies. The reason for stiffening of the a and b axes could be explained as follows. Hydrogen (deuterium) bonds to O2 by a covalent bond and to O1 by a hydrogen bond in the a–b plane. If we compare the compressibility of various O···O separations of -AlOOD reported from neutron diffraction experiments (Sano-Furukawa et al. 2008), the O···O separation of the hydrogen bond is the most compressible compared to the others that form AlO6 polyhedral edges. Above the pressure where the symmetrization occurs, the O···O separation should stiffen, because hydrogen forms a covalent bond with both O atoms, resulting in the stiffening of the a–b plane. The present result implies that symmetrization could affect the compression behavior of minerals.
The exact transition pressure of the symmetrization in -AlOOH(D) has not been determined by experimental study, but results of neutron diffraction experiments support these predictions of the symmetrization, which showed that the deuterium position moves toward the midpoint of the two O atoms as pressure increases to 9.2 GPa (Sano-Furukawa et al. 2008). Extrapolation of the O2–D and D···O1 evolution to high pressure led to the intersection at 24 GPa using a linear function, and at 16 GPa using a second-order polynomial expression. However, the observed change in the compressibility occurs at lower pressure than these previous predictions based on the extrapolations, though it is close to the lower bound of error of the second-order fit (13 GPa). This implies that the evolution of hydrogen bonding is strongly non-linear near the symmetrization pressure and a second-order polynomial extrapolations for O–H and H···O distances are not adequate. A disagreement in the transition pressure remains between the present study and theoretical studies. Applied approximation of exchange and correlation effects and correction on temperature effect are varied between the previous theoretical studies. Using the local density approximation (LDA) to treat the exchange-correlation effect, Panero and Stixrude (2004) reported that the symmetric hydrogen bond stabilizes at ambient pressure and temperature. But some studies pointed out that the LDA tends to overestimate the strength of the hydrogen bond (e.g., Lee et al. 1992). In fact, Panero and Stixrude (2004) reported that LDA gives a smaller volume than does the generalized gradient approximation (GGA). Tsuchiya et al. (2009) used GGA, but the result is for the static lattice at 0 K and the effect of temperature should be considered to compare with an experimental study.
In the present study, the pressure where the change in the compressibility was observed in -AlOOD was 2 GPa higher than that of -AlOOH. The existence of the isotope effect also suggests clearly that the change in the compressibility is related to the hydrogen bond. The symmetrization generally takes place at lower pressure in a hydrogen system than in the corresponding deuterium system. Based on the ab initio path integral simulations of ice, Benoit et al. (1998) attributed the isotope effects on the proton disordering to tunneling motion and on symmetrization to zero-point motion, respectively. Since hydrogen has half the mass of deuterium, it can overcome a potential barrier and disorder at lower pressure compared to deuterium. Subsequent symmetrization occurs when the potential barrier becomes lower than the proton vibrational level with a broad distribution at the midpoint. Therefore the symmetrization also occurs at higher pressure for hydrogen, which has higher energy of vibration than deuterium. Furthermore, expansion of the O···O separation by the geometric isotope effect should also shift the symmetrization to higher pressure.
Assuming that the change in the compressibility, observed at 10 GPa for -AlOOH and 12 GPa for -AlOOD, is induced by the symmetrization of the hydrogen bond, this is the lowest known pressure at which this phenomenon takes place among known hydrogen bonded systems. Earlier IR spectroscopic studies have shown that the OH-stretching frequency softens with increasing pressure and disappears at approximately 60 GPa in H2O-ice and 70 GPa in D2O-ice (e.g., Song et al. 1999). This behavior has been implicated as a sign of the transition to the disordering of protons by tunneling, as a step toward proton centering. In methane hydrate, an experimental study has demonstrated the transition to a new phase at 40 GPa (Machida et al. 2006), where a theoretical study predicted that proton tunneling occurs (Iitaka and Ebisuzaki 2003). The hydrogen bond is symmetric throughout its stability field at pressures above 18 GPa and the asymmetric bond only exists under the pressure range of thermodynamic metastability. In contrast, symmetrization in diaspore and brucite has been reported to occur at pressures beyond their stability fields, in excess of 110 GPa in diaspore (Friedrich et al. 2007) and 200 GPa in brucite (Mookherjee and Stixrude 2006). Probably, the strong and almost linear hydrogen bond in -AlOOH(D), present even under ambient conditions, and the effective compression of the O···O distance between the AlO6 framework, induce the symmetrization at a lower pressure than in other materials.
|
ACKNOWLEDGMENTS |
|---|
|
TopAbstractIntroductionExperimental methodsResults and discussionAcknowledgmentsReferences cited |
|---|
|
Footnotes |
|---|
MANUSCRIPT HANDLED BY IAN SWAINSON
MANUSCRIPT RECEIVED October 8, 2008; MANUSCRIPT ACCEPTED April 13, 2009
|
REFERENCES CITED |
|---|
|
TopAbstractIntroductionExperimental methodsResults and discussionAcknowledgmentsReferences cited |
|---|
Andrault, D., Fiquet, G., Guyot, F., and Hanfland, M. (1998) Pressure-induced Landau-type transition in stishovite. Science, 282, 720–724.
Aoki, K., Yamawaki, H., Sakashita, M., and Fujihisa, H. (1996) Infrared absorption study of the hydrogen-bond symmetrization in ice to 110 GPa. Physical Review B, 54, 15673–15677.[Medline]
Benoit, M., Marx, D., and Parrinello, M. (1998) Tunneling and zero-point motion in high-pressure ice. Nature, 392, 258–261.[CrossRef][GeoRef]
Chai, M. and Brown, J.M. (1996) Effect of static non-hydrostatic stress in the R lines of ruby single crystals. Geophysical Research Letters, 23, 3539–3542.[CrossRef][Web of Science][GeoRef]
Fujihara, T., Ichikawa, M., Gustafsson, T., Olovsson, I., and Tsuchida, T. (2002) Powder-neutron diffraction studies of geometric isotope and hydrogen-bonding effects in β-CrOOH. Journal of Physics and Chemistry of Solids, 63, 309–315.[CrossRef][Web of Science]
Friedrich, A., Haussühl, E., Boehler, R., Morgenroth, W., Juarez-Arellano, E.A., and Winkler, B. (2007) Single-crystal structure refinement of diaspore at 50 GPa. American Mineralogist, 92, 1640–1644.
Goncharov, A.F., Struzhkin, V.V., Somayazulu, M.S., Hemley, R.J., and Mao, H.K. (1996) Compression of ice to 210 gigapascals: Infrared evidence for a symmetric hydrogen-bonded phase. Science, 273, 218–220.[Abstract][Web of Science][Medline]
Ichikawa, M. (2000) Hydrogen-bond geometry and its isotope effect in crystals with OHO bonds—revisited. Journal of Molecular Structure, 552, 63–70.[CrossRef][Web of Science]
Iitaka, T. and Ebisuzaki, T. (2003) Methane hydrate under high pressure. Physical Review B, 68, 172105.
Komatsu, K., Kuribayashi, T., Sano, A., Ohtani, E., and Kudoh, Y. (2006) Redetermination of the high-pressure modification of AlOOH from single-crystal synchrotron data. Acta Crystallographica, E62, i216–i218.[CrossRef][Web of Science]
Li, S., Ahuja, R., and Johansson, B. (2006) The elastic and optical properties of the high-pressure hydrous phase -AlOOH. Solid State Communications, 137, 101–106.[CrossRef][Web of Science]
Machida, S., Hirai, H., Kawamura, T., Yamamoto, Y., and Yagi, T. (2006) A new high-pressure structure of methane hydrate surviving to 86 GPa and its implications for the interiors of giant icy planets. Physics of the Earth and Planetary Interiors, 155, 170–176.[CrossRef][Web of Science][GeoRef]
Matsushita, E. and Matsubara, T. (1982) Note on isotope effect in hydrogen-bonded crystals. Progress of Theoretical Physics, 67, 1–19.[CrossRef][Web of Science]
Mookherjee, M. and Stixrude, L. (2006) High-pressure proton disorder in brucite. American Mineralogist, 91, 127–134.
Ohtani, E., Litasov, K., Suzuki, A., and Kondo, T. (2001) Stability field of new hydrous phase, -AlOOH, with implications for water transport into the deep mantle. Geophysical Research Letters, 28, 3991–3993.[CrossRef][Web of Science][GeoRef]
Panero, W.R. and Stixrude, L.P. (2004) Hydrogen incorporation in stishovite at high pressure and symmetric hydrogen bonding in -AlOOH. Earth and Planetary Science Letters, 221, 421–431.[CrossRef][Web of Science][GeoRef]
Sano, A., Ohtani, E., Kubo, T., and Funakoshi, K. (2004) In situ X-ray observation of decomposition of hydrous aluminum silicate AlSiO3OH and aluminum oxide hydroxide -AlOOH at high pressure and temperature. Journal of Physics and Chemistry of Solids, 65, 1547–1554.[CrossRef][Web of Science]
Sano, A., Ohtani, E., Kondo, T., Hirao, N., Sakai, T., Sata, N., Ohishi, Y., and Kikegawa, T. (2008) Aluminous hydrous mineral -AlOOH as a carrier of hydrogen into the core-mantle boundary. Geophysical Research Letters, 35, L03303.[CrossRef]
Sano-Furukawa, A., Komatsu, K., Vanpeteghem, C.B., and Ohtani, E. (2008) Neutron diffraction study of -AlOOD at high pressure and its implication for symmetrization of the hydrogen bond. American Mineralogist, 93, 1558–1567.
Song, M., Yamawaki, H., Fujihisa, H., Sakashita, M., and Aoki, K. (1999) Infrared absorption study of Fermi resonance and hydrogen-bond symmetrization of ice up to 141 GPa. Physical Review B, 60, 12644–12650.
Suzuki, A., Ohtani, E., and Kamada, T. (2000) A new hydrous phase -AlOOH synthesized at 21 GPa and 1000 °C. Physics and Chemistry of Minerals, 27, 689–693.[CrossRef][Web of Science][GeoRef]
Takemura, K., Sahu, P. Ch., Kunii, Y., and Toma, Y. (2001) Versatile gas-loading system for diamond-anvil cells. Review of Scientific Instruments, 72, 3873–3876.[CrossRef][Web of Science]
Tsuchiya, J. and Tsuchiya, T. (2009) Elastic properties of -AlOOH under pressure: First principles investigation. Physics of Earth and Planetary Interior, 174, 122–127.[CrossRef]
Tsuchiya, J., Tsuchiya, T., Tsuneyuki, S., and Yamanaka, T. (2002) First principles calculation of a high-pressure hydrous phase, -AlOOH. Geophysical Research Letters, 29, 1909.[CrossRef]
Tsuchiya, J., Tsuchiya, T., and Tsuneyuki, S. (2005) First-principles study of hydrogen bond symmetrization of phase D under high pressure. American Mineralogist, 90, 44–49.
Vanpeteghem, C.B., Ohtani, E., and Kondo, T. (2002) Equation of state of the hydrous phase -AlOOH at room temperature up to 22.5 GPa. Geophysical Research Letters, 29, 1119.[CrossRef]
Vanpeteghem, C.B., Sano, A., Komatsu, K., Ohtani, E., and Suzuki, A. (2007) Neutron diffraction study of aluminous hydroxide -AlOOD. Physics and Chemistry of Minerals, 34, 657–661.[CrossRef][Web of Science]
Xue, X. and Kanzaki, M. (2007) High-pressure -Al(OH)3 and -AlOOH phases and isostructural hydroxides/oxyhydroxides: New structural insights from high-resolution 1H and 27Al NMR. Journal of Physics and Chemistry B, 111, 13156–13166.[CrossRef]
Xue, X., Kanzaki, M., Fukui, H., Ito, E., and Hashimoto, T. (2006) Cation order and hydrogen bonding of high-pressure phases in the Al2O3-SiO2-H2O system: An NMR and Raman study. American Mineralogist, 91, 850–861.
Zha, C., Mao, H., and Hemley, R.J. (2000) Elasticity of MgO and a primary pressure scale to 55 GPa. Proceedings of the National Academy of Sciences of the United States of America, 97, 13494–13499.
| ||||||||||||||||||||||||||||||||||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
= 0.33091(4) Å, and magnified profiles around the 010 and 120 reflections (lower). Squares in the upper panel define the magnified area shown in the lower panels. The asterisk indicates unknown peak.
