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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Pump-and-Treat Impacts on Aquifer Conditions and the Development of System-Wide Performance Strategies - 20377

The pump-and-treat (P and T) system on the Hanford Site's Central Plateau currently treats multiple contaminants within the 200-ZP-1 operable unit, including nitrate through its biological treatment processes. Although it was initially designed to support the 200-ZP-1 Remedial Action Objectives, the P and T system has evolved in use to address contaminants from other regions of the aquifer as well. The P and T influents are biogeochemically distinct, treating groundwaters with elevated concentrations of cyanide, uranium, technetium-99, and nitrate. Given the varying geochemical signatures from current and potential future sources, operational conditions, and amendments considered for treatment processes, there is a need to identify the impacts that the P and T effluent has on the aquifer, and how the aquifer affects P and T performance. To this end, laboratory efforts have focused on characterizing P and T effluent and its biogeochemical effects on the sediments through a series repacked column experiments. The P and T effluent is rich in particulate matter. A systematic inspection of this particulate matter in the P and T effluent showed significant levels of manganese/iron oxides, calcite crystals, relatively large organic matter molecules, and biomass. Therefore, the column experiments were designed and conducted for four different treatment systems: artificial groundwater, filtered P and T effluent, non-filtered P and T effluent, and chlorinated P and T effluent. Different levels of microbiologically- and geochemically-induced changes in the columns occurred and modified the flow systems. For example, physical filtration occurred in the sediments where the particulate material had accumulated in the top portion of the column. Reactive transport modeling of the laboratory experiments is being carried out so that the reaction network can be extrapolated to the field scale. These simulations will provide predictive evaluations of system performance based on P and T operational changes and aquifer mass loading and capacity estimates. This information can be used to address combined subsurface and operational challenges, such as the need for frequent well redevelopment to maintain injection capacity. This information also provides the technical basis for decisions related to the P and T system operations that support remedy optimization efforts and short- and long-term remedy decisions related to multiple operable units on the Hanford Site Central Plateau. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Synthesis of Macroscopic Single Crystals of Ge 2 Sb 2 Te 5 via Single-Shot Femtosecond Optical Excitation

Using in situ electron diffraction techniques, we demonstrate that femtosecond optical excitation above a threshold fluence of the amorphous, as-deposited, phase change material Ge 2 Sb 2 Te 5 creates large, 100 μm scale single crystals. This is 2 orders of magnitude larger than previously reported grains synthesized via photoexcitation. Transmission electron microscopy shows that these large crystals are dewetted regions with a face-centered cubic structure. Energy-dispersive X-ray spectroscopy indicates that the crystals have the same composition as the initial amorphous phase. In this work, we present a theoretical model which shows that this arises from a crossover from a nucleation-dominated crystallization regime to a growth-dominated crystallization regime, and we show that the measured grain size is consistent with Johnson–Mehl–Avrami–Kolmogorov (JMAK) crystallization theory for temperatures near the melting temperature. The ability to grow macroscopic single crystals from an amorphous material, and on arbitrary amorphous substrates, opens up a large area of potential applications, as well as new opportunities for tuning the nucleation, growth, and switching characteristics of phase-change materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Stability enhancement of an electrically tunable colloidal photonic crystal using modified electrodes with a large electrochemical potential window

The color tuning behavior and switching stability of an electrically tunable colloidal photonic crystal system were studied with particular focus on the electrochemical aspects. Photonic color tuning of the colloidal arrays composed of monodisperse particles dispersed in water was achieved using external electric field through lattice constant manipulation. However, the number of effective color tuning cycle was limited due to generation of unwanted ions by electrolysis of the water medium during electrical switching. By introducing larger electrochemical potential window electrodes, such as conductive diamond-like carbon or boron-doped diamond, the switching stability was appreciably enhanced through reducing the number of ions generated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Use of Frit‐Disc Crucible Sets to Make Solution Growth More Quantitative and Versatile

The recent availability of step‐edge, frit‐disc crucible sets (generally sold as Canfield Crucible Sets or CCS) has led to multiple innovations associated with the group's use of solution growth. The use of CCS allows for the clean separation of liquid from solid phases during the growth process. This clean separation enables the reuse of the decanted liquid, either allowing for simple, economic, savings associated with recycling expensive precursor elements or allowing for the fractionation of a growth into multiple, small steps, revealing the progression of multiple solidifications. Clean separation of liquid from solid phases also allows for the determination of the liquidus line (or surface) and the creation, or correction, of composition–temperature phase diagrams. The reuse of clean decanted liquid has also allowed to prepare liquids ideally suited for the growth of large single crystals of specific phases by tuning the composition of the melt to the optimal composition for growth of the desired phase, often with reduced nucleation sites. Finally, it is discussed how solution growth and CCS use can be harnessed to provide a plethora of composition–temperature data points defining liquidus lines or surfaces with differing degrees of precision to either test or anchor artificial intelligence and/or machine‐learning‐based attempts to augment and extend the limited experimentally determined database.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Effect of sample size on the maximum value distribution of fatigue driving forces in metals and alloys

An analytical framework is presented to predict the effects of sample size on the maximum value distribution (MVD) of the driving forces for fatigue crack formation in metals and alloys. The distribution of the maximum driving force for fatigue crack formation over the domain follows the generalized extreme value theory in the limit as the domain size increases to infinity. Here, a simulation-based analysis of microstructure influences on fatigue resistance for polycrystalline metals and alloys is very costly, and reaching those limits is intractable. This work models the MVD of Fatigue Indicator Parameters (FIPs), which serve as surrogate measures for the driving force for fatigue crack formation, at finite sample sizes prior to their convergence to a limiting extreme value distribution. Large-scale crystal plasticity finite element (CPFE) simulations of FCC Al 7075-T6 with microstructure realizations of various sizes are incorporated to calibrate and evaluate the developed framework, and a total of ∼6.5 million grains of Al 7075-T6 are examined. The calibrated analytical solution agrees well with the brute force Monte Carlo simulation results extracted from the CPFE simulations. Furthermore, the developed formulation can predict the MVD of FIPs for different sample sizes using a size-dependent parameter, and it is capable of accurately extrapolating the MVD of FIPs for much larger microstructure sample sizes than the size used for its calibration.

Crystal plasticity↗
DOE OSTI2012

Polar and nonpolar phases of BiMO{sub 3}: A review

Simple Bi-based compounds, BiMO{sub 3}, are quite interesting materials. They offer large variations in crystal symmetries, polarity, and properties. Their chemical simplicity makes them ideal systems for materials fabrications, theoretical understanding, and thin-film growths. They can only be prepared at high-pressure high-temperature conditions (except for BiFeO{sub 3}) in a bulk form. Some of them can be stabilized in thin films (M=Al, Sc, Cr, Mn, and Fe). In this review, we collect and analyze the recent experimental and theoretical results on BiMO{sub 3} with M=Al, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Ga, In, and Rh. In addition, unresolved problems and desirable future experiments are emphasized especially for the highly controversial compound BiMnO{sub 3}. - Graphical abstract: Crystal symmetries in which BiMO{sub 3} compounds crystallize. Highlights: Black-Right-Pointing-Pointer BiMO{sub 3} compounds offer large variations in crystal symmetries, polarity, and properties. Black-Right-Pointing-Pointer Experimental and theoretical results on BiMO{sub 3} were reviewed. Black-Right-Pointing-Pointer Unresolved problems and desirable future experiments are emphasized. Black-Right-Pointing-Pointer Special attention is paid on the highly controversial compound BiMnO{sub 3}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Structure analysis of a Mn-doped willemite-type compound, H{sub 0.12}(Zn{sub 1.89(3)}Mn{sub 0.05(1)}□{sub 0.06})Si{sub 1.00(1)}O{sub 4}

Large single crystals of a well-known green phosphor, Mn-doped willemite (α-Zn{sub 2}SiO{sub 4})-type compound were grown from molten MnF{sub 2}/Li{sub 2}MoO{sub 4}. In this structure Mn{sup 2+} and defects partially replace Zn{sup 2+} at two independent sites, and there are no cation species in the middle of six-membered ring channels. As a consequence of 3% defective sites (□), this structure may have protons for ensuring its electrostatic neutrality. Although the position of H{sup +} could not be clearly found the present study indicates the presence of protons in the vicinity of oxygens to make relative short H⋯O bonds below 1.6 Å. Two unusual, broad IR bands about 1780 and 2360 cm{sup −1} can be explained by disordering of strongly bonded O···H groups. This compound represents a structural unit, H{sub 0.12}(Zn{sub 1.89(3)}Mn{sub 0.05(1)}□{sub 0.06})Si{sub 1.00(1)}O{sub 4}, based on X-ray single crystal diffraction, electron microprobe, and FT-IR spectroscopy. - Graphical abstract: A willemite-type compound, H{sub 0.12}(Zn{sub 1.89(3)}Mn{sub 0.05(1)}□{sub 0.06})Si{sub 1.00(1)}O{sub 4} exhibits protons near to oxygens in the skirt of four- and six-membered ring channels, as a result of defects at two crystallographically different Zn sites. Display Omitted - Highlights: • Structure properties of a 0.05 Mn-doped α-Zn{sub 2}SiO{sub 4} compound using X-ray single crystal diffraction. • Static disorder of Zn, Mn, and defects in the framework of α-Zn{sub 2}SiO{sub 4}. • Sign of strong H⋯O bonds, observed in FT-IR spectroscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

HT-solution growth and characterisation of In{sub x}Na{sub x}Mn{sub 1-2x}WO{sub 4} (0<x≤0.26)

A new solid solution system, In{sub x}Na{sub x}Mn{sub 1–2x}WO{sub 4} (0<x=≤0.26) belonging to the MnWO{sub 4}-type multiferroics was investigated. Large single crystals were grown up to several mm in length from high-temperature oxide solutions using a solvent mixture of Na{sub 2}WO{sub 4} and Na{sub 2}W{sub 2}O{sub 7}. Quantitative doping degrees were analyzed by means of electron microprobe. Single crystal X-ray diffraction studies agreed with the polar space group P2 for In{sub x}Na{sub x}Mn{sub 1–2x}WO{sub 4}. The complexity of partial (Na{sup +}/Mn{sup 2+})- and (In{sup 3+}/Mn{sup 2+})-ordering makes their atomic sites unique, explaining the dissymmetrization from P2/c down to P2. This is also valid for the InNaW{sub 2}O{sub 8}-type Mn{sub 2y}In{sub 1-y}Na{sub 1-y}W{sub 2}O{sub 8} solid solution found as co-product in this study. Specific heat and magnetisation measurements showed a paramagnetic dilution effect from (In{sup 3+}/Na{sup +})-doping while lowering the transition temperature for the multiferroic phase AF2 of In{sub x}Na{sub x}Mn{sub 1–2x}WO{sub 4} with respect to the prototype MnWO{sub 4}. - Graphical abstract: A volume expansion around Mn2 site by (In, Na)-doping is drawn by the atomic shifts in a Mn2O{sub 6} octahedron in the atomistic structure of In{sub 0.20(2)}Na{sub 0.17(2)}Mn{sub 0.63(4)}WO{sub 4} from the respective atomic positions of In-free MnWO{sub 4}. The size and direction of arrows are scaled up for indicating the consequent local distortion. - Highlights: • HT solution crystal growth of (In, Na):MnWO{sub 4}-solid-solution compounds. • Polar space group symmetry P2 for their atomistic structures. • Magnetic properties of the multiferroic phase AF2 by (In{sup 3+}, Na{sup +})-doping. • Magnetic phase transitions.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Synthesis of La{sup 3+} doped nanocrystalline ceria powder by urea-formaldehyde gel combustion route

Highlights: Black-Right-Pointing-Pointer Nano LC synthesized by gel combustion, using urea-formaldehyde fuel for first time. Black-Right-Pointing-Pointer Largely single crystals were produced in average range of 20-30 nm. Black-Right-Pointing-Pointer La{sup 3+} doping increases cell dimension linearly. Black-Right-Pointing-Pointer La{sup 3+} doping introduces ionic point defects but does not change electronic band gap. Black-Right-Pointing-Pointer Presence of Ce{sup 3+} indicates that this synthesis route produces reactive powders. -- Abstract: Nanocrystalline ceria powders doped with various concentrations of lanthanum oxide have been prepared following gel combustion route using for the first time urea-formaldehyde as fuel. The synthesized products were characterized by XRD, FESEM, TEM, PL and UV-vis spectroscopy. Peak positions of XRD were refined and the lattice parameters were obtained by applying Cohen's method. Unit cell parameter increases with concentration of La{sup 3+} ion and the variation is consistently linear. XRD calculations showed the dependence of crystallite size on dopant concentrations at lower level. TEM observation revealed unagglomerated particles to be single crystals in the average range of 20-30 nm. Band gap of the La{sup 3+} doped ceria materials does not change with doping. Spectroscopic experiments proved the existence of Ce{sup 3+} in the formed powder.

36 MATERIALS SCIENCE↗
DOE OSTI2013

The Multi-sensor Airborne Radiation Survey (MARS) Instrument

The Multi-sensor Airborne Radiation Survey (MARS) project has developed a new single cryostat detector array design for high purity germanium (HPGe) gama ray spectrometers that achieves the high detection efficiency required for stand-off detection and actionable characterization of radiological threats. This approach, we found, is necessary since a high efficiency HPGe detector can only be built as an array due to limitations in growing large germanium crystals. Moreover, the system is ruggedized and shock mounted for use in a variety of field applications, including airborne and maritime operations.

array↗
DOE OSTI2017

Improved lithium iodide neutron scintillator with Eu 2+ activation: The elimination of Suzuki-Phase precipitates

Monovalent alkali halides such as NaI, CsI, and LiI are widely used as inorganic scintillators for radiation detection due to their light yield, the capability for the growth of large single crystals, relatively low cost, and other favorable characteristics. These materials are frequently activated through the addition of small amounts (e.g., a few hundred ppm) of elements such as thallium - or sodium in the case of CsI. The monovalent alkali halide scintillators can also be activated with low concentrations of Eu 2+ , however Eu activation has previously not been widely employed due to the non-uniform segregation of the divalent Eu dopant that leads to the formation of unwanted phases during Bridgman or other solidification crystal-growth methods. Specifically, for Eu concentrations near and above ~0.5%, Suzuki Phase precipitates form in the course of the melt-growth process, and these Suzuki Phase particles scatter the scintillation light. This adversely affects the scintillator performance via reduction in the optical transmission of the material, and depending on the crystal thickness and precipitated-particle concentration, this reduction can occur up to the point of opacity. Here we describe a post-growth process for the removal of Suzuki Phase precipitates from single crystals of the neutron scintillator LiI activated with Eu 2+ at concentrations up to and in excess of 3 wt.%, and we correlate the resulting neutron-detection performance with the thermal processing methods used to remove the Suzuki Phase particles. Furthermore, the resulting improved scintillator properties using increased Eu activator levels are applicable to neutron imaging and active interrogation systems, and pulse-height gamma-ray spectroscopy rather than pulse-shape discrimination can be used to discriminate between gamma ray and neutron interaction events.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Fabrication and testing of antimony doped bismuth tri-iodide semiconductor gamma-ray detectors

We fabricated antimony (Sb) doped bismuth tri-iodide (BiI 3 ) radiation detectors from large single crystals that were grown using the modified vertical Bridgman technique. Detectors were prepared by subjecting the crystal surfaces to different mechanical and chemical treatments. Surface quality of the detectors was evaluated using optical microscopy. The influence of surface quality on detector performance was analyzed by measuring the leakage current for each of the detectors. The radiation response of the detectors was measured using an Americium ( 241 Am) gamma-ray source at room temperature. The first successful use of BiI 3 detectors for gamma-ray spectroscopy is reported here with energy resolution of 7.5% at 59.5 keV. The mobility-lifetime product for electrons was also estimated to be about 5.2 x 10 -4 cm 2 /V.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Evaluating the pressure dependence of PZT structures using a virtual reality environment

Pb–Zr–Ti–O (PZT) perovskites span a large solid-solution range and have found widespread use due to their piezoelectric and ferroelectric properties that also span a large range. Crystal structure analysis via Rietveld refinement facilitates materials analysis via the extraction of the structural parameters. These parameters, often obtained as a function of an additional dimension (e.g., pressure), can help to diagnose materials response within a use environment. Often referred to as “ in-situ ” studies, these experiments provide an abundance of data. Viewing structural changes due to applied pressure conditions can give much-needed insight into materials performance. However, challenges exist for viewing/presenting results when the details are inherently three-dimensional (3D) in nature. For PZT perovskites, the use of polyhedra (e.g., Zr/Ti–O 6 octahedra) to view bonding/connectivity is beneficial; however, the visualization of the octahedra behavior with pressure dependence is less easily demonstrated due to the complexity of the added pressure dimension. We present a more intuitive visualization by projecting structural data into virtual reality (VR). We employ previously published structural data for Pb 0.99 (Zr 0.95 Ti 0.05 ) 0.98 Nb 0.02 O 3 as an exemplar for VR visualization of the PZT R3c crystal structure between ambient and 0.62 GPa pressure. This is accomplished via our in-house CAD2VR™ software platform and the new CrystalVR plugin. The use of the VR environment enables a more intuitive viewing experience, while enabling on-the-fly evaluation of crystal data, to form a detailed and comprehensive understanding of in-situ datasets. Discussion of methodology and tools for viewing are given, along with how recording results in video form can enable the viewing experience.

Rodriguez, Mark A. (ORCID:0000000269405044)↗
DOE OSTI2017

Synthesis, Structure, and Selective Gas Adsorption of a Single-Crystalline Zirconium Based Microporous Metal–Organic Framework

Porous metal-organic framework (MOF) materials with high thermal and water stability are desirable for various adsorption based applications. Early transition metal based MOFs such as those built on zirconium metal have been well recognized for their excellent stability toward heat and/or moisture. However, the difficulty growing large single crystals makes their structural characterization challenging. Herein we report a porous Zr-MOF, [Zr 6 O 4 (OH) 4 (cca) 6 ] (Zr-cca), which is assembled from zirconium and 4-carboxycinnamic acid (H 2 cca) under solvothermal conditions. Single crystal X-ray diffraction analysis reveals that the structure of Zr-cca is isoreticular to the prototype zirconium based MOF, UiO-66. Zr-cca shows permanent porosity upon removal of solvent molecules initially residing inside the pores, with a BET surface area of 1178 m 2 /g. As expected, it exhibits good thermal stability (stable up to 400 °C) and high resistance to acidity over a wide pH range. Evaluation of its gas adsorption performance on various hydrocarbons and fluorocarbons indicates that it preferentially adsorbs C 3 and C 4 hydrocarbons over C 2 analogues. At 30°C Zr-cca takes up more than 50 wt % of perfluorohexane and the adsorption-desorption process is fully recyclable. We have compared this material with UiO-66 and studied the underlying reasons for the difference in their adsorption performance toward perfluorohexane.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis and Properties of Single-Crystalline Na 4 Si 24

We present that Na 4 Si 24 is the precursor to Si 24 , a recently discovered allotrope of silicon. With a quasidirect band gap near 1.3 eV, Si 24 has potential to transform silicon-based optoelectronics including solar energy conversion. However, the lack of large, pure crystals has prevented the characterization of intrinsic properties and has delayed deposition-based metastable growth efforts. Here, we report an optimized synthesis methodology for single-crystalline Na 4 Si 24 with crystals approaching the millimeter-size scale with conditions near 9 GPa and 1123 K. Single-crystal diffraction was used to confirm the open-framework structure, and Na atoms remain highly mobile within the framework channels, as determined by electrical conductivity and electron energy loss spectroscopy measurements. In conclusion, an epitaxial relationship between Na 4 Si 24 and diamond cubic silicon (DC-Si), observed through high-resolution transmission electron microscopy, is proposed to facilitate the growth of high-quality Na 4 Si 24 crystals from DC-Si wafers mixed with metallic Na and could provide a viable path forward for scaling efforts of Na 4 Si 24 and Si 24 .

36 MATERIALS SCIENCE↗
DOE OSTI2021

Further Investigations of Racemic and Chiral Molecular Sieves of the STW Topology

Large single crystals of pure-silica STW-type molecular sieves are prepared using 1,2,3,4,5-pentamethylimidazolium (12345PMI) and 2-ethyl-1,3,4-trimethylimidazolium (2E134TMI) as organic structure-directing agents (OSDAs) and α-amino acid additives. The effects of the amount and type of amino acid on the crystallization of pure-silica STW materials are investigated. Room-temperature single-crystal X-ray diffractometry shows that 12345PMI better fits the STW cage than 2E134TMI and is fully consistent with computed simulations. The synthesis of an enantioenriched R-STW-type molecular sieve having a Si/Ge ratio of 2.2 is achieved using a chiral, dicationic OSDA that contains two stereocenters. Furthermore, the conformation of the chiral OSDA in the chiral framework has been obtained from a Rietveld refinement using synchrotron powder diffraction data and is the first structure refinement of an enantioenriched, inorganic molecular sieve prepared from a pure, asymmetric OSDA.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

U 8 Al 19 Si 6 , A Uranium Aluminide Silicide with a Stuffed Supercell Grown from Aluminum Flux

In this work, U 8 Al 19 Si 6 is formed from the reaction of uranium oxide and silicon in aluminum flux. Growth of this material is dependent on the presence of surface hydroxyl groups on alumina in the crucible. The compound forms as large cuboid crystals with a complex new structure that is a cubic stuffed supercell of UAl 3 (AuCu 3 parent structure type). It features a 4-fold expansion of the unit cell axis and the addition of atoms on two extra positions resulting in Pm$\bar{3n}$ symmetry. The ordered distribution of aluminum and silicon was determined using single crystal neutron diffraction. The magnetic susceptibility shows temperature independent paramagnetic behavior, while heat capacity measurements are consistent with Fermi liquid characteristics at low temperatures where the Sommerfeld constant is enhanced in comparison to that of a conventional metal. Lastly, these bulk thermodynamic properties indicate that U 8 Al 19 Si 6 is an itinerant electron Pauli paramagnet with moderately enhanced mass charge carrier quasiparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Hydrothermal Synthesis and Characterization of Novel Brackebuschite-Type Transition Metal Vanadates: Ba 2 M(VO 4 ) 2 (OH), M = V 3+ , Mn 3+ , and Fe 3+ , with Interesting Jahn–Teller and Spin-Liquid Behavior

In a new series of transition metal vanadates, namely, Ba 2 M(VO 4 ) 2 (OH) (M = V 3+ , Mn 3+ , and Fe 3+ ), was synthesized as large single crystals hydrothermally in 5 M NaOH solution at 580 °C and 1 kbar. This new series of compounds is structurally reminiscent of the brackebuschite mineral type. The structure of Ba 2 V(VO 4 ) 2 (OH) is monoclinic in space group P2 1 /m, a = 7.8783(2) Å, b = 6.1369(1) Å, c = 9.1836(2) Å, β = 113.07(3)°, V = 408.51(2) Å 3 . Moreover, the other structures are similar and consist of one-dimensional trans edge-shared distorted octahedral chains running along the b-axis. The vanadate groups bridge across edges of their tetrahedra. Structural analysis of the Ba 2 Mn(VO 4 ) 2 (OH) analogue yielded a new understanding of the Jahn–Teller effect in this structure type. Raman and infrared spectra were investigated to observe the fundamental vanadate and hydroxide vibrational modes. Finally, single-crystal temperature-dependent magnetic studies on Ba 2 V(VO 4 ) 2 (OH) reveal a broad feature over a wide temperature range with maximum at ~100 K indicating that an energy gap could exist between the antiferromagnetic singlet ground state and excited triplet states, making it potentially of interest for quantum magnetism studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗