Diffusion Driven Transient Hydrogenation in Metal Superhydrides at Extreme Conditions
In recent years, metal hydride research has become one of the driving forces of the high-pressure community, as it is believed to hold the key to superconductivity close to ambient temperature. While numerous novel metal hydride compounds have been reported and extensively investigated for their superconducting properties, little attention has been focused on the atomic and electronic states of hydrogen, the main ingredient in these novel compounds. Here, we present combined 1H-and 139La-NMR data on lanthanum superhydrides, LaHx, (x = 10.2−11.1), synthesized after laser heating at pressures above 160 GPa. Strikingly, we found hydrogen to be in a highly diffusive state at room temperature, with diffusion coefficients in the order of 10−6 cm2s−1. We found that this diffusive state of hydrogen results in a dynamic de-hydrogenation of the sample over the course of several weeks, approaching a composition similar to its precursor materials. Quantitative measurements demonstrate that the synthesized superhydrides continuously decompose over time. Transport measurements underline this conclusion as superconducting critical temperatures were found to decrease significantly over time as well. This observation sheds new light on formerly unanswered questions on the long-term stability of metal superhydrides.
Cite as:
ArXiV version: Zhou, Y., Fu, Y., Yang, M., Osmond, I., Jana, R., Nakagawa, T., Moulding, O., Buhot, J., Friedemann, S., Laniel, D., & Meier, T. (2024). Diffusion Driven Transient Hydrogenation in Metal Superhydrides at Extreme Conditions. http://arxiv.org/abs/2408.13419
Published version: Zhou, Y., Fu, Y., Yang, M., Osmond, I., Jana, R., Nakagawa, T., Moulding, O., Buhot, J., Friedemann, S., Laniel, D., & Meier, T. (2024), Nature Communications, ( 2025) 16:1135
Trace element detection in anhydrousminerals by micro-scale quantitative nuclear magnetic resonance spectroscopy
Nominally anhydrousminerals (NAMs) composing Earth’s and planetary rocks incorporate microscopic amounts of volatiles. However, volatile distribution in NAMs and their effect on physical properties of rocks remain controversial. Thus, constraining trace volatile concentrations in NAMs is tantamount to our understanding of the evolution of rocky planets and planetesimals. Here, we present an approach of trace-element quantification using micro-scale Nuclear Magnetic Resonance (NMR) spectroscopy. This approach employs the principle of enhanced mass-sensitivity in NMR microcoils. We were able to demonstrate that this method is in excellent agreement with standard methods across their respective detection capabilities. We show that by simultaneous detection of internal reference nuclei, the quantification sensitivity can be substantially increased, leading to quantifiable trace volatile element amounts of about 50 ng/g measured in a micro-meter sized single anorthitic mineral grain, greatly enhancing detection capabilities of volatiles in geologically important systems.
Cite as: Fu, Y., Tao, R., Li, S., Shen, D., Zhang, L., Wang, Z., Yang, Y., Gao, X., & Meier, T., Parts-per-billion Trace Element Detection in Anhydrous Minerals by Nano-scale NMR Spectroscopy, Nature Communications, (2024) 15:7293
Hexagonal to Monoclinic Phase Transition in Dense Hydrogen Phase III Detected by High-Pressure NMR
Conclusive crystal structure determination of the high pressure phases of hydrogen remains elusive due to lack of core electrons and vanishing wave vectors, rendering standard high-pressure experimental methods moot. Ab-initio DFT calculations have shown that structural polymorphism might be solely resolvable using high-resolution nuclear magnetic resonance (NMR) spectroscopy at mega-bar pressures, however technical challenges have precluded such experiments thus far. Here, we present in-situ high-pressure high-resolution NMR experiments in hydrogen phase III between 181 GPa and 208 GPa at room temperature. Our spectra suggest that at lower pressures phase III adopts a hexagonal P6122 crystal structure, transitioning into a monoclinic C2/c phase at about 197 GPa. The high resolution spectra are in excellent agreement with earlier structural and spectral predictions and underline the possibility of a subtle P6122 → C2/c phase transition in hydrogen phase III. These experiments show the importance of a combination of ab-initio calculations and low-Z sensitive spectral probes in high-pressure science in elucidating the structural complexity of the most abundant element in our universe.
Cite as: Yang, M., Zhou, Y., Jana, R., Nakagawa, T., Fu, Y., & Meier, T. (2024). Hexagonal to Monoclinic Phase Transition in Dense Hydrogen Phase III Detected by High-Pressure NMR., arXiv:2407.19368
Parts-per-billion Trace Element Detection in Anhydrous Minerals by Micro-scale Quantitative NMR
Nominally anhydrous minerals (NAMs) composing Earth’s and planetary rocks incorporate mi- croscopic amounts of volatiles. However, volatile distribution in NAMs and their effect on physical properties of rocks remain controversial. Thus, constraining trace volatile concentrations in NAMs is tantamount to our understanding of the evolution of rocky planets and planetesimals. Here, we present a novel approach of trace-element quantification using micro-scale Nuclear Magnetic Res- onance (NMR) spectroscopy. This approach employs the principle of enhanced mass-sensitivity in NMR microcoils formerly used in in-situ high pressure experiments. We were able to demonstrate that this method is in excellent agreement with standard methods across their respective detection capabilities. We show that by simultaneous detection of internal reference nuclei, the quantification sensitivity can be substantially increased, leading to quantifiable trace volatile element amounts of about 50 wt-ppb measured in a micro-meter sized single anorthitic mineral grain, greatly enhancing detection capabilities of volatiles in geologically important systems.
Cite as: Fu, Y., Tao, R., Li, S., Shen, D., Zhang, L., Wang, Z., Yang, Y., Gao, X., & Meier, T. (2024). Parts-per-billion Trace Element Detection in Anhydrous Minerals by Nano-scale NMR Spectroscopy, arXiv:2404.15713v1
Direct hydrogen quantification in high- pressure metal hydrides
High-pressure metal hydride (MH) research evolved into a thriving field within condensed matter physics following the realization ofmetallic compounds showing phonon mediated near room-temperature superconductivity. However, severe limitations in determining the chemi- cal formula of the reaction products, especially with regards to their hydrogen content, impedes a deep understanding of the synthesized phases and can lead to significantly erroneous conclusions. Here, we present a way to directly access the hydrogen content of MH solids synthesized at high pressures in (laser-heated) diamond anvil cells using nuclear magnetic resonance spectroscopy. We show that this method can be used to investigate MH compounds with a wide range of hydrogen content, from MHx with x = 0.15 (CuH0.15) to x ≲ 6.4 (H6±0.4S5).
Cite as: Meier, T., Laniel, D., & Trybel, F. (2023). Direct hydrogen quantification in high-pressure metal hydrides. Matter and Radiation at Extremes, 8(1), 018401. https://doi.org/10.1063/5.0119159
Silica-water superstructure and one-dimensional
superionic conduit in Earth’s mantle
Water in Earth’s deep interior is predicted to be hydroxyl (OH−) stored in nominally anhydrous minerals, profoundly modulating both structure and dynamics of Earth’s mantle. Here, we use a high-dimensional neuro-network potential and machine learning algorithms to investigate the weight percent water incorporation in stishovite, a main constituent of the subducted oceanic crust. We found that stishovite and water prefer forming medium- to long-range ordered superstructures, featuring one-dimensional (1D) water channels. Syn- thesizing single crystals of hydrous stishovite, we verified the ordering of OH− groups in the water channels through optical and nuclear magnetic resonance spectroscopy and found an average H-H distance of 2.05(3) Å, confirming simulation results. Upon heating, H atoms were predicted to behave fluid-like inside the channels, leading to an exotic 1D superionic state. Water-bearing stishovite could feature high ionic mobility and strong electrical anisotropy, manifesting as electrical heterogeneity in Earth’s mantle.
Cite as: Li, J., Lin, Y., Meier, T., Liu, Z., Yang, W., Mao, H., Zhu, S., & Hu, Q. (2023). Silica-water superstructure and one-dimensional superionic conduit in Earth’s mantle. Science Advances, 9(35). https://doi.org/10.1126/sciadv.adh3784
Structural independence of hydrogen-bond symmetrisation dynamics at extreme pressure conditions
The experimental study of hydrogen-bonds and their symmetrization under extreme condi- tions is predominantly driven by diffraction methods, despite challenges of localising or probing the hydrogen subsystems directly. Until recently, H-bond symmetrization has been addressed in terms of either nuclear quantum effects, spin crossovers or direct structural transitions; often leading to contradictory interpretations when combined. Here, we present high-resolution in-situ 1H-NMR experiments in diamond anvil cells investigating a range of systems containing linear O-H⋯ O units at pressure ranges of up to 90 GPa covering their respective H-bond symmetrization. We found pronounced minima in the pressure depen- dence of the NMR resonance line-widths associated with a maximum in hydrogen mobility, precursor to a localisation of hydrogen atoms. These minima, independent of the chemical environment of the O-H⋯ O unit, can be found in a narrow range of oxygen oxygen distances between 2.44 and 2.45 Å, leading to an average critical oxygen-oxygen distance of 2.443 Å.
Cite as: Meier, T., Trybel, F., Khandarkhaeva, S., Laniel, D., Ishii, T., Aslandukova, A., Dubrovinskaia, N., & Dubrovinsky, L. (2022). Structural independence of hydrogen-bond symmetrisation dynamics at extreme pressure conditions. Nature Communications, 13(1), 3042. https://doi.org/10.1038/s41467-022-30662-4
High-pressure synthesis of seven lanthanum hydrides with a significant variability of hydrogen content
The lanthanum-hydrogen system has attracted significant attention following the report of superconductivity in LaH10 at near-ambient temperatures and high pressures. Phases other than LaH10 are suspected to be synthesizedbased on both powder X-ray diffraction and resistivity data, although they have not yet been identified. Here, we present the results of our single-crystal X-ray diffraction studies on this system, supported by density functional theory calculations, which reveal an unexpected chemical and structural diversity of lanthanum hydrides synthesized in the range of 50 to 180GPa. Seven lantha- num hydrides were produced, LaH3, LaH~4, LaH4+δ, La4H23, LaH6+δ, LaH9+δ, and LaH10+δ, and the atomic coordinates of lanthanum in their structures deter- mined. The regularities in rare-earth element hydrides unveiled here provide clues to guide the search for other synthesizable hydrides and candidate high- temperature superconductors. The hydrogen content variability in lanthanum hydrides and the samples’ phase heterogeneity underline the challenges related to assessing potentially superconducting phases and the nature of electronic transitions in high-pressure hydrides.
Cite as: Laniel, D., Trybel, F., Winkler, B., Knoop, F., Fedotenko, T., Khandarkhaeva, S., Aslandukova, A., Meier, T., Chariton, S., Glazyrin, K., Milman, V., Prakapenka, V., Abrikosov, I. A., Dubrovinsky, L., & Dubrovinskaia, N. (2022). High-pressure synthesis of seven lanthanum hydrides with a significant variability of hydrogen content. Nature Communications, 13(1), 6987. https://doi.org/10.1038/s41467-022-34755-y
Absence of proton tunneling during the hydrogen-bond symmetrization in δ-AlOOH
δ-AlOOH is of significant crystallochemical interest due to a subtle structural transition near 10 GPa from a hydrogen bond and their interplay. We perform a series of density functional theory-based simulations in P21nm to a Pnnm structure, the nature and origin of hydrogen disorder, the symmetrization of the O-H ···O combination with high-pressure nuclear magnetic resonance (NMR) experiments on δ-AlOOH up to 40 GPa with the goal to better characterize the hydrogen potential and therefore the nature of hydrogen disorder. Simulations predict a phase transition in agreement with our NMR experiments at 10 − 11GPa and hydrogen bond symmetrization at 14.7GPa. Calculated hydrogen potentials do not show any double-well character and there is no evidence for proton tunneling in our NMR data
Cite as: Trybel, F., Meier, T., Wang, B., & Steinle-Neumann, G. (2021). Absence of proton tunneling during the hydrogen-bond symmetrization in δ−AlOOH. Physical Review B, 104(10), 104311. https://doi.org/10.1103/PhysRevB.104.104311
In situ high-pressure nuclear magnetic resonance crystallography in one and two dimensions
Recent developments in in situ nuclear magnetic resonance (NMR) spectroscopy under extreme conditions have led to the observation of a wide variety of physical phenomena that are not accessible with standard high-pressure experimental probes. However, inherent di- or quadrupolar line broadening in diamond anvil cell (DAC)-based NMR experiments often limits detailed investigation of local atomic structures, especially if different phases or local environments coexist. Here, we describe our progress in the development of high-resolution NMR experiments in DACs using one- and two-dimensional homonuclear decoupling experiments at pressures up to the megabar regime. Using this technique, spectral resolutions of the order of 1 ppm and below have been achieved, enabling high-pressure structural analysis. Several examples are presented that demonstrate the wide applicability of this method for extreme conditions research.
Cite as: Meier, T., Aslandukova, A., Trybel, F., Laniel, D., Ishii, T., Khandarkhaeva, S., Dubrovinskaia, N., & Dubrovinsky, L. (2021). In situ high-pressure nuclear magnetic resonance crystallography in one and two dimensions. Matter and Radiation at Extremes, 6(6), 068402. https://doi.org/10.1063/5.0065879
Nuclear spin coupling crossover in dense molecular hydrogen
One of the most striking properties of molecular hydrogen is the coupling between molecular rotational properties and nuclear spin orientations, giving rise to the spin isomers ortho- and para-hydrogen. At high pressure, as intermolecular interactions increase significantly, the free rotation of H2 molecules is increasingly hindered, and consequently a modification of the coupling between molecular rotational properties and the nuclear spin system can be anticipated. To date, high-pressure experimental methods have not been able to observe nuclear spin states at pressures approaching 100 GPa and consequently the effect of high pressure on the nuclear spin statistics could not be directly measured. Here, we present in-situ high-pressure nuclear magnetic resonance data on molecular hydrogen in its hexagonal phase I up to 123 GPa at room temperature. While our measurements confirm the presence of ortho-hydrogen at low pressures, above 70 GPa, we observe a crossover in the nuclear spin statistics from a spin-1 quadrupolar to a spin-1/2 dipolar system, evidencing the loss of spin isomer distinction. These observations represent a unique case of a nuclear spin crossover phenomenon in quantum solids.
Cite as: Meier, T., Laniel, D., Pena-Alvarez, M., Trybel, F., Khandarkhaeva, S., Krupp, A., Jacobs, J., Dubrovinskaia, N., & Dubrovinsky, L. (2020). Nuclear spin coupling crossover in dense molecular hydrogen. Nature Communications, 11(1), 6334. https://doi.org/10.1038/s41467-020-19927-y
Proton dynamics in high-pressure ice-VII from density functional theory
Using a density functional theory based approach, we explore the symmetrization and proton dynamics in ice-VII, for which recent high-pressure NMR experiments indicate significant proton dynamics in the pressure- range of 20–95 GPa. We directly sample the potential seen by the proton and find a continuous transition from double- to single-well character over the pressure range of 2 to 130 GPa accompanied by proton dynamics, in agreement with the NMR experiments
Cite as: Trybel, F., Cosacchi, M., Meier, T., Axt, V. M., & Steinle-Neumann, G. (2020). Proton dynamics in high-pressure ice-VII from density functional theory. Physical Review B, 102(18), 184310. https://doi.org/10.1103/PhysRevB.102.184310
Proton mobility in metallic copper hydride from high-pressure nuclear magnetic resonance
The atomic and electronic structures of Cu2H and CuH have been investigated by high-pressure nuclear magnetic resonance spectroscopy up to 96 GPa, X-ray diffraction up to 160 GPa, and density functional theory-based calculations. Metallic Cu2H was synthesized at a pressure of 40 GPa, and semimetallic CuH at 90 GPa, found stable up to 160 GPa. For Cu2H, experiments and computations show an anomalous increase in the electronic density of state at the Fermi level for the hydrogen 1s states and the formation of a hydrogen network in the pressure range 43–58 GPa, together with high 1H mobility of ∼10^−7 cm^2/s. A comparison of these observations with results on FeH suggests that they could be common features in metal hydrides.
Cite as: Meier, T., Trybel, F., Criniti, G., Laniel, D., Khandarkhaeva, S., Koemets, E., Fedotenko, T., Glazyrin, K., Hanfland, M., Bykov, M., Steinle-Neumann, G., Dubrovinskaia, N., & Dubrovinsky, L. (2020). Proton mobility in metallic copper hydride from high-pressure nuclear magnetic resonance. Physical Review B, 102(16), 1–8. https://doi.org/10.1103/PhysRevB.102.165109
Improving resolution of solid state NMR in dense molecular hydrogen
Recent advancements in radio frequency resonator designs have led to the implementation of nuclear magnetic resonance in diamond anvil cells (DACs) at pressures well above 100 GPa. However, a relatively low resolution and the absence of decoupling sequences complicate the analysis of the results of solid state NMR in DACs. Here, we present the first application of homonuclear Lee-Goldburg (LG) decoupling on high density molecular hydrogen up to 64 GPa. Lenz lens based two-dimensional resonator structures were found to generate a homogeneous B1 field across sample cavities as small as 12 pl, a prerequisite for optimal decoupling. At ideal LG conditions, the broad 1H resonance of molecular ortho-hydrogen was narrowed 1600-fold, resulting in linewidths of 3.1 ppm.
Cite as: Meier, T., Khandarkhaeva, S., Jacobs, J., Dubrovinskaia, N., & Dubrovinsky, L. (2019). Improving resolution of solid state NMR in dense molecular hydrogen. Applied Physics Letters, 115(13), 131903. https://doi.org/10.1063/1.5123232
Table-top nuclear magnetic resonance system for high-pressure studies with in situ laser heating
High pressure Nuclear Magnetic Resonance (NMR) is known to reveal the behavior ofmatter under extreme conditions. However, until now, significant maintenance demands, space requirements, and high costs ofsuperconducting magnets render its application unfeasible for regular modern high pressure laboratories. Here, we present a table-top NMR system based on permanent Halbach magnet arrays with a diameter of 25 cm and height of4 cm. At the highest field of1013 mT, 1H-NMR spectra ofice VII have been recorded at 25 GPa and ambient temperature. The table-top NMR system can be used together with double sided laser heating setups. Feasibility of high-pressure high-temperature NMR was demonstrated by collecting 1H-NMR spectra ofH2O at 25 GPa and 1063(50) K. The change in the signal intensity in a laser-heated NMR diamond anvil cell has been found to yield a convenient way for temperature measurements.
Cite as: Meier, T., Dwivedi, A. P., Khandarkhaeva, S., Fedotenko, T., Dubrovinskaia, N., & Dubrovinsky, L. (2019). Table-top nuclear magnetic resonance system for high-pressure studies with in situ laser heating. Review of Scientific Instruments, 90(12), 123901. https://doi.org/10.1063/1.5128592
Under Pressure to Superconductivity
Superconductivity is one of the most fascinating physical phenomena in solid state physics; however, an application at technologically relevant temperatures around 300 K has not yet been realized. In modern high-pressure laboratories, it has been possible to synthesize hydrogen-rich metal hydrides that become superconducting at 260 K - temperatures found in the freezer. Our group at the Bavarian Geoinstitute (BGI) at the University of Bayreuth has developed a method with which the electronic properties of the hydrogen atoms in these substances can be investigated.
Cite as: Meier, T. (2019). Unter Hochdruck zur Supraleitung. Physik in Unserer Zeit, 50(6), 267–268. https://doi.org/10.1002/piuz.201970606
Pressure-Induced Hydrogen-Hydrogen Interaction in Metallic FeH Revealed by NMR
Knowledge of the behavior of hydrogen in metal hydrides is the key for understanding their electronic properties. Here, we present an 1H-NMR study of cubic FeH up to 202 GPa. We observe a distinct deviation from the ideal metallic behavior between 64 and 110 GPa that suggests pressure-induced H-H interactions. Accompanying ab-initio calculations support this result, as they reveal the formation of an intercalating sublattice of electron density, which enhances the hydrogen contribution to the electronic density of states at the Fermi level. This study shows that pressure-induced H-H interactions can occur in metal hydrides at much lower compression and larger H-H distances than previously thought and stimulates an alternative pathway in the search for novel high-temperature superconductors.
Cite as: Meier, T., Trybel, F., Khandarkhaeva, S., Steinle-Neumann, G., Chariton, S., Fedotenko, T., Petitgirard, S., Hanfland, M., Glazyrin, K., Dubrovinskaia, N., & Dubrovinsky, L. (2019). Pressure-Induced Hydrogen-Hydrogen Interaction in Metallic FeH Revealed by NMR. Physical Review X, 9(3), 031008. https://doi.org/10.1103/PhysRevX.9.031008
At Its Extremes: NMR at Giga-Pascal Pressures
Implementation of nuclear magnetic resonance in high pressure vessels is among the most demanding technological endeavours of the field, owing to inherently low signal amplitudes, low sensitivities of the resonator set-ups, and samples which are both difficult to handle and to access in the finished experimental set-up. The following chapter presents a review of the basic principles of generating pressures in excess of 1 GPa (10.000 atm), followed by a summary of suitable NMR resonators. Additionally, recent high pressure experiments on correlated and uncorrelated electronic system at pressures as high as 30 GPa will be covered.
Cite as: Meier, T. (2018). At Its Extremes: NMR at Giga-Pascal Pressures. In G. Webb (Ed.), Annual Reports on NMR Spectroscopy (93rd ed., pp. 1–74). Elsevier. https://doi.org/10.1016/bs.arnmr.2017.08.004
Journey to the centre of the Earth: Jules Vernes’ dream in the laboratory from an NMR perspective
High pressure nuclear magnetic resonance is among the most challenging fields of research for NMR spectroscopists due to inherently low signal intensities, ultra-small samples that are barely accessible, and overall extremely harsh conditions in the sample cavity of modern high pressure vessels. This review aims to provide a comprehensive overview of the topic of high pressure research and its fairly young and brief relationship with NMR.
Cite as: Meier, T. (2018). Journey to the centre of the Earth: Jules Vernes’ dream in the laboratory from an NMR perspective. Progress in Nuclear Magnetic Resonance Spectroscopy, 106–107, 26–36. https://doi.org/10.1016/j.pnmrs.2018.04.001
Observation of nuclear quantum effects and hydrogen bond symmetrisation in high pressure ice
Hydrogen bond symmetrisations in H-bonded systems triggered by pressure-induced nuclear quantum effects (NQEs) is a long-known concept but experimental evidence in high-pressure ices has remained elusive with conventional methods. Theoretical works predicted quantum- mechanical tunneling of protons within water ices to occur at pressures above 30 GPa, and the H-bond symmetrisation transition to occur above 60 GPa. Here we used 1H-NMR on high-pressure ice up to 97 GPa, and demonstrate that NQEs govern the behavior of the hydrogen bonded protons in ice VII already at significantly lower pressures than previously expected. A pronounced tunneling mode was found to be present up to the highest pressures of 97 GPa, well into the stability field of ice X, where NQEs are not anticipated in a fully symmetrised H-bond network. We found two distinct transitions in the NMR shift data at about 20 GPa and 75 GPa attributed to the step-wise symmetrisation of the H-bond.
Cite as: Meier, T., Petitgirard, S., Khandarkhaeva, S., & Dubrovinsky, L. (2018). Observation of nuclear quantum effects and hydrogen bond symmetrisation in high pressure ice. Nature Communications, 9(1), 2766. https://doi.org/10.1038/s41467-018-05164-x
NMR at pressures up to 90 GPa
The past 15 years have seen an astonishing increase in Nuclear Magnetic Resonance (NMR) sensitivity and accessible pressure range in high-pressure NMR experiments, owing to a series ofnew developments of NMR spectroscopy applied to the diamond anvil cell (DAC). Recently, with the application of electro- magnetic lenses, so-called Lenz lenses, in toroidal diamond indenter cells, pressures of up to 72 GPa with NMR spin sensitivities of about 10^12 spin/Hz^1/2 has been achieved. Here, we describe the implementation of a refined NMR resonator structure using a pair of double stage Lenz lenses driven by a Helmholtz coil within a standard DAC, allowing to measure sample volumes as small as 100 pl prior to compression. With this set-up, pressures close to 100 GPa could be realised repeatedly, with enhanced spin sensitivi- ties of about 10^11 spin/Hz^1/2. The manufacturing and handling of these new NMR-DACs is relatively easy and straightforward, which will allow for further applications in physics, chemistry, or biochemistry.
Cite as: Meier, T., Khandarkhaeva, S., Petitgirard, S., Körber, T., Lauerer, A., Rössler, E., & Dubrovinsky, L. (2018). NMR at pressures up to 90 GPa. Journal of Magnetic Resonance, 292, 44–47. https://doi.org/10.1016/j.jmr.2018.05.002
Magnetic flux tailoring through Lenz lenses for ultrasmall samples: A new pathway to high-pressure nuclear magnetic resonance
A new pathway to nuclear magnetic resonance (NMR) spectroscopy for picoliter-sized samples (including those kept in harsh and extreme environments, particularly in diamond anvil cells) is introduced, using inductively coupled broadband passive electromagnetic lenses, to locally amplify the magnetic field at the isolated sample, leading to an increase in sensitivity. The lenses are adopted for the geometrical restrictions imposed by a toroidal diamond indenter cell and yield signal-to-noise ratios at pressures as high as 72 GPa at initial sample volumes of only 230 pl. The corresponding levels of detection are found to be up to four orders of magnitude lower compared to formerly used solenoidal microcoils. Two-dimensional nutation experiments on long-chained alkanes, CnH2n+2 (n = 16 to 24), as well as homonuclear correlation spectroscopy on thymine, C5H6N2O2,wereusedto demonstrate the feasibility of this approach for higher-dimensional NMR experiments, with a spectral resolution of at least 2 parts per million. This approach opens up the field of ultrahigh-pressure sciences to one of the most versatile spectro- scopic methods available in a pressure range unprecedented up to now.
Cite as: Meier, T., Wang, N., Mager, D., Korvink, J. G., Petitgirard, S., & Dubrovinsky, L. (2017). Magnetic flux tailoring through Lenz lenses for ultrasmall samples: A new pathway to high-pressure nuclear magnetic resonance. Science Advances, 3(12), eaao5242. https://doi.org/10.1126/sciadv.aao5242
High-sensitivity NMR beyond 200,000 atmospheres of pressure
Pressure-induced changes in the chemical or electronic structure of solids require pressures well into the Giga-Pascal (GPa) range due to the strong bonding. Anvil cell designs can reach such pressures, but their small and mostly inaccessible sample chamber has severely hampered NMR experiments in the past. With a new cell design that has a radio frequency (RF) micro-coil in the high pressure chamber, NMR experiments beyond 20 Giga-Pascal are reported for the first time. 1H NMR of water shows sensitivity and resolution obtained with the cells, and 63Cu NMR on a cuprate superconductor (YBa2Cu3O(7-d)) demonstrates that single-crystals can be investigated, as well. 115In NMR of the ternary chalcogenide AgInTe2 discovers an insulator-metal transition with shift and relaxation measurements. The pressure cells can be mounted easily on standard NMR probes that fit commercial wide-bore magnets with regular cryo- stats for field- and temperature-dependent measurements ready for many applications in physics and chemistry.
Cite as: Meier, T., Reichardt, S., & Haase, J. (2015). High-sensitivity NMR beyond 200,000 atmospheres of pressure. Journal of Magnetic Resonance, 257, 39–44. https://doi.org/10.1016/j.jmr.2015.05.007
Anvil cell gasket design for high pressure nuclear magnetic resonance experiments beyond 30 GPa
Nuclear magnetic resonance (NMR) experiments are reported at up to 30.5 GPa of pressure using
radiofrequency (RF) micro-coils with anvil cell designs. These are the highest pressures ever reported with NMR, and are made possible through an improved gasket design based on nano-crystalline powders embedded in epoxy resin. Cubic boron-nitride (c-BN), corundum (α-Al2O3), or diamond based composites have been tested, also in NMR experiments. These composite gaskets lose about 1/2 of their initial height up to 30.5 GPa, allowing for larger sample quantities and preventing damages to the RF micro-coils compared to precipitation hardened CuBe gaskets. It is shown that NMR shift and resolution are less affected by the composite gaskets as compared to the more magnetic CuBe. The sensitivity can be as high as at normal pressure. The new, inexpensive, and simple to engineer gaskets are thus superior for NMR experiments at high pressures.
Cite as: Meier, T., & Haase, J. (2015). Anvil cell gasket design for high pressure nuclear magnetic resonance experiments beyond 30 GPa. Review of Scientific Instruments, 86(12), 123906. https://doi.org/10.1063/1.4939057
High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures: A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions
Nuclear Magnetic Resonance (NMR) is one of the most important techniques for the study of condensed matter systems, their chemical structure, and their electronic properties. The application of high pressure enables one to synthesize new materials, but the response of known materials to high pressure is a very useful tool for studying their electronic structure and developing theories. For example, high-pressure synthesis might be at the origin of life; and understanding the behavior of small molecules under extreme pressure will tell us more about fundamental processes in our universe. It is no wonder that there has always been great interest in having NMR available at high pressures. Unfortunately, the desired pressures are often well into the Giga-Pascal (GPa) range and require special anvil cell devices where only very small, secluded volumes are available. This has restricted the use of NMR almost entirely in the past, and only recently, a new approach to high- sensitivity GPa NMR, which has a resonating micro-coil inside the sample chamber, was put forward. This approach enables us to achieve high sensitivity with experiments that bring the power of NMR to Giga-Pascal pressure condensed matter research. First applications, the detection of a topological electronic transition in ordinary aluminum metal and the closing of the pseudo-gap in high-temperature superconductivity, show the power of such an approach. Meanwhile, the range of achievable pressures was increased tremendously with a new generation of anvil cells (up to 10.1 GPa), that fit standard-bore NMR magnets. This approach might become a new, important tool for the investigation of many condensed matter systems, in chemistry, geochemistry, and in physics, since we can now watch structural changes with the eyes of a very versatile probe.
Cite as: Meier, T., & Haase, J. (2014). High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures : A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions. Journal of Visualized Experiments, 92(92), e52243. https://doi.org/10.3791/52243
Moissanite anvil cell design for Giga-Pascal nuclear magnetic resonance
A new design of a non-magnetic high-pressure anvil cell for nuclear magnetic resonance (NMR) experiments at Giga-Pascal pressures is presented, which uses a micro-coil inside the pressurized region for high-sensitivity NMR. The comparably small cell has a length of 22 mm and a diameter of 18 mm, so it can be used with most NMR magnets. The performance of the cell is demonstrated with external-force vs. internal-pressure experiments, and the cell is shown to perform well at pressures up to 23.5 GPa using 800 μm 6H-SiC large cone Boehler-type anvils. (1)H, (23)Na, (27)Al, (69)Ga, and (71)Ga NMR test measurements are presented, which show a resolution of better than 4.5 ppm, and an almost maximum possible signal-to-noise ratio.
Cite as: Meier, T., Herzig, T., & Haase, J. (2014). Moissanite anvil cell design for Giga-Pascal nuclear magnetic resonance. The Review of Scientific Instruments, 85(4), 043903. https://doi.org/10.1063/1.4870798