I19-Small Molecule Single Crystal Diffraction
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Juan
Angel Sans
,
Francisco Javier
Manjon
,
André Luis
De Jesus Pereira
,
Javier
Ruiz-Fuertes
,
Catalin
Popescu
,
Alfonso
Muñoz
,
Plácida
Rodríguez-Hernández
,
Julio
Pellicer-Porres
,
Vanesa Paula
Cuenca-Gotor
,
Julia
Contreras-Garcia
,
Jordi
Ibañez
,
Virginia
Monteseguro
Diamond Proposal Number(s):
[22223]
Abstract: The structural, vibrational and electronic properties of the compressed β-Sb2O3 polymorph, a.k.a. mineral valentinite, have been investigated in a joint experimental and theoretical study up to 23 GPa. The compressibility of the lattice parameters, unit-cell volume and polyhedral unit volume as well as the behaviour of its Raman- and IR-active modes under compression have been interpreted on the basis of ab initio theoretical simulations. Valentinite shows an unusual compressibility up to 15 GPa with four different pressure ranges, whose critical pressures are 2, 4, and 10 GPa. The pressure dependence of the main structural units, the lack of soft phonons, and the electronic density charge topology address the changes at those critical pressures to isostructural phase transitions of degree higher than 2. In particular, the transitions at 2 and 4 GPa can be ascribed to the changes in the interaction between the stereochemically-active lone electron pairs of Sb atoms under compression. The changes observed above 10 GPa, characterized by a general softening of several Raman- and IR-active modes, point to a structural instability prior to the 1st-order transition occurring above 15 GPa. Above this pressure, a tentative new high-pressure phase (s.g. Pcc2) has been assigned by single-crystal and powder X-ray diffraction measurements.
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Mar 2021
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[8176, 9366]
Open Access
Abstract: We report results from a series of diamond-anvil-cell synchrotron X-ray diffraction and largevolume- press experiments, and calculations, to investigate the phase diagram of commercial polycrystalline high-strength Ti-6Al-4V alloy in pressure-temperature space. Up to ~30 GPa and 886 K, Ti- 6Al-4V is found to be stable in the hexagonal-close-packed, or alpha phase. The effect of temperature on the volume expansion and compressibility of alpha-Ti-6Al-4V is modest. The martensitic alpha→omega (hexagonal) transition occurs at ~30 GPa, with both phases coexisting until further compression to ~38-40 GPa completes the transition to the omega phase. Between 300 K and 844 K the alpha→omega transition appears to be independent of temperature. Omega-Ti-6Al-4V is stable to ~91 GPa and 844 K, the highest combined pressure and temperature reached in these experiments. Pressure-volume-temperature equations-of-state for the alpha and omega phases of Ti- 6Al-4V are generated and found to be similar to pure Ti. A pronounced hysteresis is observed in the omega-Ti-6Al-4V on decompression, with the hexagonal structure reverting back to the alpha phase at pressures below ~9 GPa at room temperature, and at a higher pressure at elevated temperatures. Based on our data, we estimate the Ti-6Al-4V alpha-beta-omega triple point to occur at ~900 K and 30 GPa, in good agreement with our calculations.
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Jan 2021
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I15-Extreme Conditions
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Juan A.
Sans
,
Rosario
Vilaplana
,
E. Lora
Da Silva
,
Catalin
Popescu
,
Vanesa P.
Cuenca-gotor
,
Adrián
Andrada-chacón
,
Javier
Sánchez-benitez
,
Oscar
Gomis
,
André L. J.
Pereira
,
Plácida
Rodríguez-hernández
,
Alfonso
Muñoz
,
Dominik
Daisenberger
,
Braulio
Garcia-domene
,
Alfredo
Segura
,
Daniel
Errandonea
,
Ravhi S.
Kumar
,
Oliver
Oeckler
,
Philipp
Urban
,
Julia
Contreras-garcia
,
Francisco J.
Manjón
Abstract: High pressure X-ray diffraction, Raman scattering, and electrical measurements, together with theoretical calculations, which include the analysis of the topological electron density and electronic localization function, evidence the presence of an isostructural phase transition around 2 GPa, a Fermi resonance around 3.5 GPa, and a pressure-induced decomposition of SnSb2Te4 into the high-pressure phases of its parent binary compounds (α-Sb2Te3 and SnTe) above 7 GPa. The internal polyhedral compressibility, the behavior of the Raman-active modes, the electrical behavior, and the nature of its different bonds under compression have been discussed and compared with their parent binary compounds and with related ternary materials. In this context, the Raman spectrum of SnSb2Te4 exhibits vibrational modes that are associated but forbidden in rocksalt-type SnTe; thus showing a novel way to experimentally observe the forbidden vibrational modes of some compounds. Here, some of the bonds are identified with metavalent bonding, which were already observed in their parent binary compounds. The behavior of SnSb2Te4 is framed within the extended orbital radii map of BA2Te4 compounds, so our results pave the way to understand the pressure behavior and stability ranges of other “natural van der Waals” compounds with similar stoichiometry.
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Jul 2020
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[9548, 7533]
Open Access
Abstract: We present an experimental study of the high-pressure, high-temperature behaviour of cerium up to $\sim$22 GPa and 820 K using angle-dispersive x-ray diffraction and external resistive heating. Studies above 820 K were prevented by chemical reactions between the samples and the diamond anvils of the pressure cells. We unambiguously measure the stability region of the orthorhombic \textit{oC}4 phase and find it reaches its apex at 7.1 GPa and 650 K. We locate the $\alpha$-\textit{cF}4 -- \textit{oC}4 -- \textit{tI}2 triple point at 6.1 GPa and 640 K, 1 GPa below the location of the apex of the \textit{oC}4 phase, and 1-2 GPa lower than previously reported. We find the $\alpha$-\textit{cF}4 $\rightarrow$ \textit{tI}2 phase boundary to have a positive gradient of 280 K/GPa, less steep than the 670 K/GPa reported previously, and find the \textit{oC}4 $\rightarrow$ \textit{tI}2 phase boundary to lie at higher temperatures than previously found. We also find variations as large as 2-3 GPa in the transition pressures at which the \textit{oC}4 $\rightarrow$ \textit{tI}2 transition takes place at a given temperature, the reasons for which remain unclear. Finally, we find no evidence that the $\alpha$-\textit{cF}4 $\rightarrow$ \textit{tI}2 is not second order at all temperatures up to 820 K.
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Mar 2020
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[23122]
Open Access
Abstract: The high-pressure and high-temperature structural and chemical stability of ruthenium has been investigated via synchrotron X-ray diffraction using a resistively heated diamond anvil cell. In the present experiment, ruthenium remains stable in the hcp phase up to 150 GPa and 960 K. The thermal equation of state has been determined based upon the data collected following four different isotherms. A quasi-hydrostatic equation of state at ambient temperature has also been characterized up to 150 GPa. The measured equation of state and structural parameters have been compared to the results of ab initio simulations performed with several exchange-correlation functionals. The agreement between theory and experiments is generally quite good. Phonon calculations were also carried out to show that hcp ruthenium is not only structurally but also dynamically stable up to extreme pressures. These calculations also allow the pressure dependence of the Raman-active E2g mode and the silent B1g mode of Ru to be determined.
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Oct 2019
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I15-Extreme Conditions
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S.
Anzellini
,
D.
Errandonea
,
Simon
Macleod
,
P.
Botella
,
D.
Daisenberger
,
J. M.
De’ath
,
J.
Gonzalez-platas
,
J.
Ibáñez
,
M. I.
Mcmahon
,
K. A.
Munro
,
C.
Popescu
,
J.
Ruiz-fuertes
,
C. W.
Wilson
Diamond Proposal Number(s):
[15864]
Abstract: Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murnaghan equation of state with a Berman-type thermal expansion model.
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Aug 2018
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[19846]
Open Access
Abstract: The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000 K, by combining optical observations, x-ray diffraction, and ab-initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300 K up to the melting temperature. The pressure at which c/a reaches √3 (≈10 GPa) is not affected by temperature. When this ideal axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple poly-crystals. In addition, a noticeable change in the pressure dependence of c/a takes place at the same pressure. Both phenomena can be caused by an isomorphic second-order phase transition induced by pressure in Zn. The reported melt curve extends previous results from 24 to 135 GPa. The pressure dependence obtained for the melting temperature is accurately described by using a Simon–Glatzel equation. The determined melt curve agrees with previous low-pressure studies and with shock-wave experiments, with a melting temperature of 5060(30) K at 135 GPa. Finally, a thermal equation of state is reported, which at room-temperature agrees with the literature.
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Jun 2018
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Tomas
Marqueno
,
David
Santamaria-perez
,
Javier
Ruiz-fuertes
,
Raquel
Chuliá-jordán
,
Jose L.
Jordá
,
Fernando
Rey
,
Chris
Mcguire
,
Abby
Kavner
,
Simon
Macleod
,
Dominik
Daisenberger
,
Catalin
Popescu
,
Placida
Rodriguez-hernandez
,
Alfonso
Muñoz
Abstract: We report the formation of an ultrahigh CO2-loaded pure-SiO2 silicalite-1 structure at high pressure (0.7 GPa) from the interaction of empty zeolite and fluid CO2 medium. The CO2-filled structure was characterized in situ by means of synchrotron powder X-ray diffraction. Rietveld refinements and Fourier recycling allowed the location of 16 guest carbon dioxide molecules per unit cell within the straight and sinusoidal channels of the porous framework to be analyzed. The complete filling of pores by CO2 molecules favors structural stability under compression, avoiding pressure-induced amorphization below 20 GPa, and significantly reduces the compressibility of the system compared to that of the parental empty one. The structure of CO2-loaded silicalite-1 was also monitored at high pressures and temperatures, and its thermal expansivity was estimated.
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May 2018
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David
Santamaria Perez
,
Tomas
Marqueño
,
Simon
Macleod
,
Javier
Ruiz-fuertes
,
Dominik
Daisenberger
,
Raquel
Chulia-jordan
,
Daniel
Errandonea
,
Jose Luis
Jorda
,
Fernando
Rey
,
Chris
Mcguire
,
Adam
Makhluf
,
Abby
Kavner
,
Catalin
Popescu
Abstract: The crystal structure of CO2-filled pure-SiO2 LTA zeolite has been studied at high pressures and temperatures using synchrotron-based x-ray powder diffraction. Its structure consists of 13 CO2 guest molecules, 12 of them accommodated in the large α-cages and 1 in the β-cages, giving a SiO2:CO2 stoichiometric ratio smaller than 2. The structure remains stable under pressure up to 20 GPa with a slight pressure-dependent rhombohedral distortion, indicating that pressure-induced amorphization is prevented by the insertion of guest species in this open framework. The ambient-temperature lattice compressibility has been determined. In situ high-pressure resistive-heating experiments up to 750 K allow us to estimate the thermal expansivity at P~5 GPa. Our data confirm that the insertion of CO2 reverses the negative thermal expansion of the empty zeolite structure. No evidence of any chemical reaction was observed. The possibility of synthesizing a silicon carbonate at high temperatures and higher pressures is discussed in terms of the evolution of C – O and Si – O distances between molecular and framework atoms.
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May 2017
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I15-Extreme Conditions
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R.
Vilaplana
,
Juan Angel
Sans Tresserras
,
F.j.
Manjón
,
A.
Andrada-chacón
,
J.
Sánchez-benítez
,
Catalin
Popescu
,
Oscar
Gomis
,
André Luis
De Jesus Pereira
,
Braulio
Garcia Domene
,
P.
Rodríguez-hernández
,
A.
Muñoz
,
Dominik
Daisenberger
,
O.
Oeckler
Diamond Proposal Number(s):
[9102]
Abstract: We report high-pressure X-ray diffraction and electrical measurements of the topological insulator SnBi2Te4 at room temperature. The pressure dependence of the structural properties of the most stable phase of SnBi2Te4 at ambient conditions (trigonal phase) have been experimentally determined and compared with results of our ab initio calculations. Furthermore, a comparison of SnBi2Te4 with the parent compound Bi2Te3 shows that the central TeSnTe trilayer, which substitutes the Te layer at the center of the TeBiTeBiTe layers of Bi2Te3, plays a minor role in the compression of SnBi2Te4. Similar to Bi2Te3, our resistance measurements and electronic band structure simulations in SnBi2Te4 at high pressure suggest that this compound exhibits a pressure-induced electronic topological transition or Lifshitz transition between 3.5 and 5.0 GPa.
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Nov 2016
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