188,914 research outputs found
P-induced crystal fluid interaction: the case of ERI and OFF topology
No full textThe P-induced intrusion of molecules or solvated ions within the nanocavities of open-framework minerals, such as zeolites, has been extensively investigated during last decades (e.g., Gatta et al., 2018, and references within). This peculiar property might be exploited to tailor new multifunctional materials or to enhance industrial catalytic processes involving zeolites (Comboni et al., 2020). In addition, from a geological point
of view, a constraint of this phenomena might shed light on the role played by zeolites as fluid carriers in the upper Earth crust, e.g., during the early subduction of altered basalts or oceanic sediments. The aim of the present study is to characterize the high-pressure behavior, promoting the crystal-fluid interaction, on two different natural zeolites species belonging to the ABC-6 family: erionite (AABAAC) and offretite (AAB)
(ERI and OFF topology, respectively). Similarities of the framework between these two species resulted in quite common intergrowth, at least in natural samples (Passaglia et al., 1998). Samples were compressed in non-penetrating and penetrating P-transmitting fluids (PTFs). Investigations were conducted via in-situ high pressure single-crystal synchrotron X-ray diffraction, using a diamond anvil cell (DAC), at the ID15b beamline of ESRF (Grenoble, France) and P02.2 of PETRA-III (Hamburg, Germany). Different PTFs have been employed during the experiments: non-penetrating i) silicone oil and daphne oil (7575) and potentially penetrating, ii) alcohols: water mixtures, iii) pure H2O, iv) Ne. The obtained unit-cell P-V patterns revealed the adsorption of H2O molecules within the structural cavities; in addition, the structure refinements allowed to describe the deformation mechanisms as well as the location of the adsorbed molecules. Interestingly, the magnitude of the absorption phenomena in natural erionite appeared to be comparable with what observed in synthetic zeolites (i.e., AlPO4-5, Lotti et al., 2016), highlighting the great potential of erionite as a mineralogical carrier of fluids in the upper Earth crust.
Comboni D., Pagliaro F., Lotti P., Gatta G.D., Merlini M., Milani S., Migliori M., Giordano G., Catizzone E., Collings I.E. & Hanfland M. (2020) - The elastic behavior of zeolitic frameworks: The case of MFI type zeolite under high-pressure methanol intrusion. Catal. Today, 345, 88-96.
Gatta G.D., Lotti P. & Tabacchi G. (2018) - The effect of pressure on open-framework silicates: elastic behaviour and crystal-fluid interaction. Phys. Chem. Miner., 45, 115-138.
Lotti P., Gatta G.D., Comboni., Merlini M., Pastero L. & Hanfland M. (2016) - AlPO4-5 zeolite at high pressure: Crystalfluid interaction and elastic behavior. Microp. Mesop. Mater., 228, 158-167.
Passaglia E., Artioli G. & Gualtieri A. (1998) - Crystal chemistry of the zeolites erionite and offretite. Am. Mineral., 83, 577-589
P-induced crystal fluid interaction: the case of ERI and OFF topologies
No full textThe P-induced intrusion of molecules or solvated ions within the nanocavities of open-framework minerals,
such as zeolites, has been extensively investigated during last decades (e.g., Gatta et al., 2018, and references
within). This peculiar property might be exploited to tailor new multifunctional materials or to enhance
industrial catalytic processes involving zeolites (Comboni et al., 2020). In addition, from a geological point
of view, a constraint of this phenomena might shed light on the role played by zeolites as fluid carriers in the
upper Earth crust, e.g., during the early subduction of altered basalts or oceanic sediments. The aim of the
present study is to characterize the high-pressure behavior, promoting the crystal-fluid interaction, on two
different natural zeolites species belonging to the ABC-6 family: erionite (AABAAC) and offretite (AAB)
(ERI and OFF topology, respectively). Similarities of the framework between these two species resulted in
quite common intergrowth, at least in natural samples (Passaglia et al., 1998). Samples were compressed in
non-penetrating and penetrating P-transmitting fluids (PTFs).
Investigations were conducted via in-situ high pressure single-crystal synchrotron X-ray diffraction, using
a diamond anvil cell (DAC), at the ID15b beamline of ESRF (Grenoble, France) and P02.2 of PETRA-III
(Hamburg, Germany). Different PTFs have been employed during the experiments: non-penetrating i) silicone
oil and daphne oil (7575) and potentially penetrating, ii) alcohols: water mixtures, iii) pure H2O, iv) Ne.
The obtained unit-cell P-V patterns revealed the adsorption of H2O molecules within the structural cavities;
in addition, the structure refinements allowed to describe the deformation mechanisms as well as the location of
the adsorbed molecules. Interestingly, the magnitude of the absorption phenomena in natural erionite appeared
to be comparable with what observed in synthetic zeolites (i.e., AlPO4-5, Lotti et al., 2016), highlighting the
great potential of erionite as a mineralogical carrier of fluids in the upper Earth crust.
Comboni D., Pagliaro F., Lotti P., Gatta G.D., Merlini M., Milani S., Migliori M., Giordano G., Catizzon
T- and P-stability and thermo-elastic behavior of the ABW-compounds TlAlSiO4 and CsAlSiO4
No full textT- and P-stability and thermo-elastic behavior
of the ABW-compounds TlAlSiO4 and CsAlSiO4
Paolo Lotti,a G. Diego Gattaa,b, Domenico Caputoc, Marco Merlinia,
Paolo Apreac, Andrea Lausid, Carmine Colellac
aDipartimento di Scienze della Terra, Università degli Studi di Milano, Milano, Italy
bCNR - Istituto di Cristallografia, Sede di Bari, Bari, Italy
cDipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università degli Studi di Napoli “Federico II”, Napoli, Italy
dSincrotrone Trieste S.C.p.A. di Interesse Nazionale, Basovizza, Trieste, Italy
[email protected]
A large number of microporous compounds sharing the ABW framework topology have so far been reported in the literature. These compounds show a significant chemical variability, leading to interesting magnetic, optical or structural properties (see e.g. [1] and references therein). The ABW framework can be described as made by sheets of six-membered rings of tetrahedra, in which three tetrahedra have apical oxygen atoms pointing upward (U) and three downward (D), according to a “UUUDDD” scheme. The sheets are interconnected through the apical oxygen atoms, giving rise to elliptical 8-membered ring channels, where the extraframework population is hosted. The latter is generally represented by monovalent cations, with (as Li-ABW) or without (as Rb-, Cs- or Tl-ABW) H2O molecules. Only a few studies have so far been devoted to the phase-stability fields and thermo-elastic behavior of ABW compounds, in response to T and P.
In this study, we focused our attention to two synthetic ABW compounds: TlAlSiO4 and CsAlSiO4, which gain interest for the pollutant and/or toxic nature of the hosted extraframework cations (Tl+ or Cs+). TlAlSiO4 has been investigated up to 950 °C (at room-P) and up to 8 GPa (at room-T) by means of in-situ synchrotron powder diffraction with a diamond anvil cell and with a high-temperature furnace [2]. No phase transition has been observed within the T- and P-range investigated. A II-order Birch-Murnaghan equation of state (II-BM EoS) fit of the P-V data led to a refined bulk modulus KV0 = 48.8(2) GPa. A polynomial fit of the T-V data led to a refined volume thermal expansion coefficient αV,25°C = 4.44(3)*10-5 K-1. CsAlSiO4 has been investigated up to 1000 °C (at room-P) and up to 10 GPa (at room-T) by means of in-situ synchrotron powder diffraction [3]. As for the Tl-analogue, no phase transitions have been observed within the T- and P-range investigated. A II-BM EoS fit of the P-V data gave a refined KV0 = 41.3(3) GPa. A polynomial fit of the T-V data led to a refined αV,20°C = 3.63(1)*10-5 K-1. Both the studied ABW-compounds show a remarkably anisotropic thermo-elastic pattern, resembling that of “layered materials” (e.g. phyllosilicates), where the stacking direction of the 6mR-sheets is significantly more compressible and expandable than the sheets plane. Such a behavior appears to be governed by the nature of the ABW topology of the framework. The high stability and flexibility of TlAlSiO4 and CsAlSiO4 at high-T (at room-P) and high-P (at room-T) suggest these compounds as functional materials for the fixation and storage of the Tl+ and Cs+.
[1] V. Kahlenberg, R.X. Fischer, W.H. Baur, Z. Kristallogr. 2001, 216, 489-494.
[2] G.D. Gatta, P. Lotti, M. Merlini, D. Caputo, P. Aprea, A. Lausi, C. Colella, Micropor. Mesopor. Mater. 2014, submitted.
[3] G.D. Gatta, M. Merlini, P. Lotti, A. Lausi, M. Rieder, Micropor. Mesopor. Mater. 2013, 163, 147-152
P-induced crystal-fluid interactions in erionite-K : a natural nano-sponge
No full textThe study of the high-pressure behaviour of microporous compounds, e.g. zeolites, experienced, in last decades, a raising interest related to the P-mediated intrusion of solvated ions/molecules, from the so-called “penetrating” P-transmitting fluids into the zeolitic structural voids [1]. These phenomena may occur when the molecules have a kinetic diameter that allow their adsorption into the structural cavities and may be potentially exploited in the tailoring of functional materials. In this study, we have investigated the P¬-mediated intrusion of H2O and alcohols molecules, carried by the P¬-transmitting fluids, into the structural cavities of the natural zeolite erionite-K, by means of in situ high-pressure single-crystal synchrotron X-ray diffraction, using a diamond anvil cell, at the Xpress beamline of the Elettra synchrotron (Trieste, Italy). Erionites are a series of minerals belonging to the zeolite group, with a wide chemical variability expressed as solid solution among three end-members: erionite-Ca, erionite-K and erionite-Na. The samples we analysed are classified as erionite-K, with an average chemical formula: K2.31Na0.02Ca2.15Mg0.69Ba0.04Sr0.02(Al9.00Si27.19)O72·18.66H2O.
The erionite-type framework is based on the repetition of six-membered rings with a sequence AABAAC. This stacking leads to a structure characterized by the presence of large cages (23-hedron, called “erionite-cage”), superposed along the c-axis, hosting most of the extra-framework population.
To constrain the crystal-fluid interaction, we performed two high-P ramps using different P-transmitting media: 1) with the non-penetrating silicone oil, up to 2.60(5) GPa, and 2) with the potentially penetrating methanol:ethanol:H2O = 16:3:1 (hereafter mew) mixture, up to 4.97(5) GPa.
Silicone oil data allowed the refinement of the isothermal bulk modulus of the pristine sample, expressed as KV0 = 44(1) GPa (βV0 = KV0-1 = 0.0227(5) GPa-1, where βV0 is the bulk volume compressibility), after a fit of a II-order Birch-Murnaghan equation of state to the experimental P-V data.
The P-V data from the mew ramp unambiguously show a marked decrease in compressibility, which is unequivocally related to the P-induced intrusion of H2O (and possibly alcohols) molecules from the P-transmitting fluid. This phenomenon, which appears to be irreversible in decompression, apparently occurs in three different steps, approximately at 0.2, 1.2 and 2 GPa. In addition, the magnitude of the intrusion appears to be comparable with that observed for synthetic zeolites as SiO2-ferrierite [2] or AlPO4-5 [3] and this is somehow unexpected if we consider that the studied erionite is a natural sample, with structural cavities largely filled by extra-framework cations and H2O molecules.
Further experiments, with different classes of potentially penetrating fluids, will allow to fully understand and constrain the P-induced adsorption phenomena in natural erionite.
[1] Gatta GD, Lotti P, Tabacchi G Phys. Chem. Miner. 2018 45, 115-138.
[2] Lotti P, Arletti R, Gatta GD, Quartieri S, Vezzalini G, Merlini M, Dmitriev V, Hanfland M Micropor. Mesopor. Mater. 2015 218, 42-54.
[3] Lotti P, Gatta GD, Comboni D, Merlini M, Pastero L, Hanfland M. Micropor. Mesopor. Mater. 2016 228, 158-167
Cancrinite-group minerals ([CAN]-framework type) at non-ambient conditions
No full textAll the isotypic minerals of the cancrinite-group share the [CAN]-framework type, built up by layers of single six-membered rings of tetrahedra centered in an “A” or “B” position, according to the ABAB stacking sequence. The resulting framework has the following secondary building units: 12-membered ring channels parallel to the [0001] axis, bound by columns of base-sharing cages, and the so-called can units. A large chemical variability is shown by both natural and non-natural isotypic compounds. Among the natural species, the majority shows an alumino-silicate framework (Al6Si6O24), and two subgroups can be identified according to the extraframework content of the can units: the cancrinite- and the davyne-subgroups, showing Na-H2O and Ca-Cl chains, respectively. Several cations, anionic and/or molecular groups lie in the channels.
The description of the phase-stability fields and the of the thermo-elastic behavior of the cancrinite-group minerals play a key role in the study of the natural and industrial processes where these compounds are primary constituents (a short summary of which is in [1,2]).
We aim to model the thermo-elastic behavior and (P,T)-induced structure evolution of these isotypic compounds, with a focus on the influence played by the different extraframework constituents on the structure deformation mechanisms. The study is restricted to the chemical compositions commonly occurring in Nature, delimited by the (CO3)-rich and (SO4)-rich end-members within the two aforementioned subgroup: cancrinite {[(Na,Ca)6(CO3)1.2-1.7][Na2(H2O)2][Al6Si6O24]} and vishnevite {[(Na,Ca,K)6(SO4)][Na2(H2O)2][Al6Si6O24]}, balliranoite {[(Na,Ca)6(CO3)1.2-1.7][Ca2Cl2][Al6Si6O24]} and davyne {[(Na,Ca,K)6((SO4),Cl)][Ca2Cl2][Al6Si6O24]}, respectively. The high-pressure and low-temperature (T < 293 K) studies of the carbonate end-members (i.e. cancrinite and balliranoite) have been performed by means of in situ single-crystal X-ray diffraction. The results [1-4] show that, though sharing a similar volume compressibility and thermal expansivity, these minerals have a different thermo-elastic anisotropy, being more pronounced in cancrinite. This is due to different (P,T)-induced structure deformation mechanisms, likely governed by the different coordination environment of the cage population. An in situ high-temperature (293 ≤ T(K) ≤ 823(7)) single-crystal X-ray diffraction study of cancrinite, allowed the description of thermo-elastic behavior and anisotropy. An irreversible dehydration process takes place at 748(7) K. Preliminary results of the high-pressure studies of the sulfatic end-members (i.e. vishnevite and davyne) are available. A clear change of the elastic behavior of vishnevite, with an increase of compressibility, is shown between 2.47(2)-3.83(2) GPa. A similar increase of compressibility was also reported for cancrinite at 4.62-5.00(2) GPa.
References. [1] Lotti, P., Gatta, G.D., Rotiroti, N., Cámara, F. (2012): Am. Mineral., 97, 872-882; [2] Gatta, G.D., Lotti, P., Kahlenberg, V. (2013): Micropor. Mesopor. Mater., 174, 44-53; [3] Gatta, G.D., Lotti, P., Kahlenberg, V., Haefeker, U. (2012): Miner. Mag., 76, 933-948; [4] Lotti, P., Gatta, G.D., Rotiroti, N., Cámara, F., Harlow, G.E. (2013): Z. Kristallogr., in press
The role of temperature on P-induced crystal-fluid interaction : a study on LAU and HEU topologies
No full textNatural zeolites can be found in soil, oceanic basalts as well as sediments and diagenetic environments. Their peculiar reversible hydration property (i.e., the ability to adsorb and release H2O molecules) and the ability to overhydrate under pressure, make them suitable carriers of fluids in the upper Earth crust during the early stage of subduction. Despite the extensive study of high-pressure and high-temperature behavior of natural and synthetic zeolites over the last decades, few studies have yet combined the effects of both conditions. Experiments at combined high pressure and high temperature might provide valuable insights on the crystal-fluid interaction preocesses occurring in nature at the geological conditions of stability of zeolites, especially when these microporous compounds can act as carriers and moderators of the circulating fluids.
In this study, the in situ combined high-pressure and high-temperature behavior of two commonly occurring natural zeolites, heulandite and laumontite, was investigated. The P-induced crystal-fluid interaction of these two zeolites was studied at ambient-T by Comboni et al. [1] for laumontite and Seryotkin [2] for heulandite. These results have been used as benchmarks to evaluate the role of temperature on the crystal-fluid interaction. In-situ, HTHP single-crystal synchrotron X-ray diffraction experiments were conducted using a diamond anvil cell (DAC) surrounded by a resistive heater at the ID15b beamline at the European Synchrotron Radiation Facility in Grenoble (France). The setup allowed to reach temperatures of about 150(2)°C. Pressure was measured using the ruby fluorescence technique while temperature was monitored using a thermocouple located very close to the P-chamber, allowing a precise determination of both these variables. The results obtained were consistent with those calculated using the Au-powder pattern.
The results showed that temperature significantly increased the kinetics of H2O adsorption in laumontite, with respect to the compressional behavior at room conditions, leading to a volume expansion observable already at pressures < 5 kbar. It was previously found that laumontite hydrated at ambient conditions after 24 hours, while the presence of a temperature gradient reduced the time at about 15 minutes. Even for heulandite, the comparison with literature data suggests that a higher H2O adsorption rate was observed when the thermal gradient was applied.
References
[1] Comboni D., Gatta G.D., Lotti P., Merlini M. & Hanfland M. 2018. Crystal-fluid interactions in laumontite. Microporous Mesoporous Mater., 263, 86-95.
[2] Seryotkin, Y.V. 2015. Influence of content of pressure-transmitting medium on structural evolution of heulandite: Single-crystal X-ray diffraction study. Microporous and Mesoporous Mater., 214, 127-135
From Nature to materials science: (Cs,K)Al4Be5B11O28 (londonite) as a super-hard material
No full textLondonite is a rare Cs-bearing mineral with ideal chemical formula (Cs,K)Al4Be4(B,Be)12O28 (with Cs > K). The building block units of the structure of londonite are represented by clusters of four edge-sharing Al-octahedra linked to B- and Be-tetrahedra. Gatta et al. (2011) investigated the phase stability and the elastic behavior of londonite up to 4.85(5) GPa (at room-T) and up to 1000°C (at room-P) by in situ X-ray powder diffraction data, but no structure refinements were possible. Whether no phase transition was observed within the pressure-range investigated, londonite
proved to have an extremely high bulk modulus: KP0 = 280(12) GPa, similar to those of carbides (e.g., B4C with KP0 ~ 245-306 GPa; Lazzari et al., 1999; Fujii et al., 2010). Considering the thermo-elastic properties and the significantly high fraction of boron (B2O3 ~50 wt%), the synthetic counterparts of londonite could be considered a potential inorganic host for 10B in composite neutron-absorbing materials. Furthermore the high content of Cs makes londonite-type materials potential host for nuclear waste. However, to date, because of the absence of structural data at high pressure and to the modest P-range investigated by Gatta et al. (2011), a comprehensive description of the P-induced deformation mechanisms at the atomic scale is still missing. In this study, the isothermal compressional behaviour of londonite is studied by in situ single-crystal synchrotron X-ray diffraction experiment with a diamond anvil cell up to 25 GPa. The compressional behavior and the deformation mechanisms at the atomic scale are described. Londonite does not experience any phase transition or change of the compressional behavior within the P-range investigated.Fujii, T., Mori, Y., Hyodo, H., Kimura, K. (2010): X-ray diffraction study of B4C under high pressure. J. Phys. Conf. Ser., 215,
012011.
Gatta, G.D., Vignola, P., Lee, Y. (2011): Stability of (Cs,K)Al4Be5B11O28 (londonite) at high pressure and high temperature: a
potential neutron absorber material. Phys. Chem. Miner., 38, 429-434.
Lazzari, R., Vast, N., Besson, J.M., Baroni, S., Dal Corso, A. (1999): Atomic structure and vibrational properties of icosahedral B4C
boron carbide. Phys. Rev. Letters, 83, 3230-3233
Cancrinite-group minerals at non-ambient conditions: vishnevite and davyne
No full textIsotypic minerals of the cancrinite-group share the [CAN]-framework type, built up by layers of single six-membered rings of tetrahedra centered in an “A” or “B” position, according to the ABAB stacking sequence. In order to describe a model for the thermo-elastic behavior of these isotypic compounds, we have recently investigated the high-pressure (up to ca. 8 GPa) and low-temperature (100 ≤ T (K) ≤ 293) characteristics of the (CO3)-rich end-members cancrinite {[(Na,Ca)6(CO3)1.2-1.7][Na2(H2O)2][Al6Si6O24]} and balliranoite {[(Na,Ca)6(CO3)1.2-1.7][Ca2Cl2][Al6Si6O24]}, by means of in situ single crystal X-ray diffraction. The results [1-4] showed that, though sharing a similar volume compressibility and thermal expansivity, these minerals have a different thermo-elastic anisotropy, being more pronounced in cancrinite. This is due to different (P,T)-induced structure deformation mechanisms, governed by the different coordination environment of the extraframework population within the cages. We are extending our investigation on (SO4)-rich members of the group, and in particular on vishnevite {[(Na,Ca,K)6(SO4)][Na2(H2O)2][Al6Si6O24], analogue of cancrinite} and davyne {[(Na,Ca,K)6(SO4,Cl)][Ca2Cl2][Al6Si6O24], analogue of balliranoite}. High-pressure and low-temperature in situ single-crystal X-ray diffraction experiments are currently in progress. A preliminary analysis allowed an early description of their high-pressure behavior. Vishnevite, which is apparently stable up to 7.40(2) GPa, shows a change of the compressional behavior, with an increase of compressibility, between 2.47(2)-3.83(2) GPa. Experimental data within the range 0.0001-2.47(2) GPa have been fitted with a II-order Birch-Murnaghan equation of state (II-BM EoS, K' = 4), giving the following refined elastic parameters: V0 = 733.5(4) Å3, KV0 = 51(1) GPa; a0 = 12.762(2) Å, Ka0 = 59.8(9) GPa; c0 = 5.2013(9) Å, Kc0 = 38.0(6) GPa. A III-BM EoS fit of the experimental data within the range 3.83(2)-7.40(2) gave: V0 = 757(6) Å3, KV0 = 30(3) GPa KV' = 2.6(5); a0 = 12.84(2) Å, Ka0 = 40(3) GPa, Ka' = 1.8(4); c0 = 5.33(4) Å, Kc0 = 16(3) GPa, Kc' = 3.6(5). A re-arrangement of the extra-framework population within the channels appear to control the observed change of the compressional behavior. A significantly less pronounced increase of compressibility was observed for cancrinite at 4.62(2)-5.00(2) GPa [2]. Davyne does not show any loss of crystallinity nor a change of compressional behavior up to 7.18(2) GPa. Experimental data have been fitted with a III-BM Eos, leading to the following refined parameters: V0 = 761.6(4) Å3, KV0 = 46.8(9) GPa, KV' = 3.6(3); a0 = 12.815(2) Å, Ka0 = 50.3(9) GPa, Ka' = 4.0(3); c0 = 5.355(1) Å, Kc0 = 41.6(9) GPa, Kc' = 2.9(2), showing a strong similarity with the elastic behavior of balliranoite at high pressure[4].
[1] G.D. Gatta, P. Lotti, V. Kahlenberg, U. Haefeker Miner. Mag. 2012, 76, 933.
[2] P. Lotti, G.D. Gatta, N. Rotiroti, F. Cámara Am. Mineral. 2012, 97, 872.
[3] G.D. Gatta, P. Lotti, V. Kahlenberg, Micropor. Mesopor. Mater. 2013, 174, 44.
[4] P. Lotti, G.D. Gatta, N. Rotiroti, F. Cámara, G.E. Harlow Z. Kristallogr. 2013 (in press)
Comparative thermo-elastic behaviour of the isotypic cancrinite and balliranoite
No full textThe high-pressure behaviour and the P-induced structure evolution of a natural cancrinite from
Cameroun (Na6.59Ca0.93[Si6.12Al5.88O24](CO3)1.04F0.41•2H2O, a = 12.5976(6) Å, c =5 .1168(2) Å,
space group: P63) were investigated by in situ single-crystal X-ray diffraction under hydrostatic
conditions up to 6.63(2) GPa with a diamond anvil cell[1]. The P-V data were fitted with an
isothermal Birch-Murnaghan-type equation of state (BM EoS) truncated to the 3rd-order, giving
the following elastic parameters: V0 = 702.0(7) Å3, KV0 = 51(2) GPa and KV' = 2.9(4). Linearized
BM EoS was used to fit the a-P and c-P data, giving the following parameters: a0 = 12.593(5) Å,
Ka0 = 64(4) GPa, Ka' = 4.5(9), and c0 = 5.112(3) Å, Kc0 = 36(1) GPa, Kc' = 1.9(3). A subtle change
of the elastic behaviour appears to occur at P > 4.62 GPa, and so the elastic behaviour was also
described on the basis of BM EoS valid between 0.0001 – 4.62 and 5.00 – 6.63 GPa, respectively.
The high-pressure structure refinements allowed the description of the main deformation
mechanisms responsible for the anisotropic compression of cancrinite. The low-temperature
structure evolution of the same natural cancrinite was also investigated by means of in-situ single-crystal
X-ray diffraction[2]. The V-T data exhibit a trend without any evident thermoelastic
anomaly, with a thermal expansion coefficient αV = 38(7) •10^(-6) K^(-1) (between 100 and 293 K).
Seven structure refinements showed that the same mechanisms observed at high pressure, mainly
govern the low-T structure evolution.
A study of a natural sample of balliranoite
(Na4.47Ca2.86K0.10[Si5.96Al6.04O24](CO3)0.62(SO4)0.33Cl2.03, a = 12.680(1) Å, c = 5.3141(5) Å, S.G.:
P63) at high pressure and low temperature is in progress. Preliminary P-V data up to 4.93 GPa
were fitted with a BM EoS truncated to the 2nd order (II-BM EoS), giving the following refined
parameters: V0 = 735.6(9) Å3, KV0 = 48.0(14) GPa. A fit with a II-BM EoS, applied to the P-V
data of cancrinite within the range 0.0001-4.62 GPa, gave the following parameters: V0 = 702.5(5)
Å3, KV0 = 48.8(6) GPa, showing similar volume compressibility. However, a different elastic
anisotropy is observed (Ka0:Kc0 = 2.14:1 in cancrinite; Ka0:Kc0 = 1.40:1 in balliranoite). Structure
refinements of balliranoite from high pressure and low temperature diffraction data will lead to
the description of the P/T-induced structure evolution, allowing a comparative crystal-chemistry
analysis of this class of materials.
References
1.P. Lotti, G.D. Gatta, N. Rotiroti, F. Càmara Am. Mineral. (2012), 97, 872−882.
2.G.D. Gatta, P. Lotti, V. Kahlenberg, U. Haefeker Mineral Mag. (2012, in press)
The role of temperature in P-induced crystal fluid interaction: the case of LAU and HEU topology
No full textZeolites are a class of open-framework aluminosilicate minerals commonly present in soil, oceanic basalts and sediments and diagenetic environments. Zeolites may act as fluid carriers in the upper Earth crust during the early subduction stage thanks to their unique features: the reversible hydration (i.e., the ability of adsorb and release H2O molecules or other small molecules, e.g., CO2, CH4, SO2) and the ability to overhydrate. During the last decades, the high-pressure (HP) and high-temperature (HT) behavior of natural and synthetic zeolites have been intensively investigated but, at the best of our knowledge, no experiments have ever been conducted combining the effects of both thermodynamic variable. Experiments at these conditions (i.e., simulating the PT gradient), using a H2O-based solution as P-transmitting fluids (PTFs), provide a realistic description of crystal-fluid interaction phenomena. In this study, we have investigated the HPHT behavior of heulandite and laumontite, two of the most common natural zeolites, whose presence have been described in a wide range of natural environments. The characterization of the crystal-fluid interaction induced by P in these two species has already been performed by Comboni et al. (2018) and Seryotkin (2015) for laumontite and heulandite, respectively, and was adopted as reference in order to evaluate the T gradient effect. In-situ HPHT single-crystal synchrotron X-ray diffraction experiments were performed at the ID15b beamline, at the ESRF, Grenoble (France). The set-up, easily
reproducible, consist of a membrane-driven diamond anvil cell (DAC) placed in a resistive heater which allowed to increase the T up to 150(2)°C. Pressure was determined by the ruby florescence method, while temperature was measured using a thermocouple located very close to the P-chamber, allowing a precise determination of both (results were consistent with the values calculated by the Au-powder pattern).
Results of the P-V pattern in laumontite clearly indicated that temperature enhances the H2O adsorption, giving rise to a volume expansion at P < 5 kbar. Previous experimental finding highlighted that hydration of laumontite occurs at ambient condition after ~ 24h, while with the presence of a T gradient required no more that 20 min. Concerning heulandite, preliminary data seems to suggest a higher H2O adsorption. if compared
to that governed by the effect of P only.
Comboni D., Gatta G.D., Lotti P., Merlini M. & Hanfland M. (2018) - Crystal-fluid interactions in laumontite. Microp.
Mesop. Mater., 263, 86-95.
Seryotkin Y.V. (2015) - Influence of content of pressure-transmitting medium on structural evolution of heulandite: Single-crystal X-ray diffraction study. Microp. Mesop. Mater., 214, 127-135
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