Single Crystal Phase Research Articles

Optical grating and THz polarizer based on normal grade single crystal diamond fast fabricated by fs laser

In this paper, we have researched the fs laser induced the phase transition in the normal grade single crystal diamond plates. The results show that the optical properties and electric properties of the irradiated region closely relate to the degree of the phase transition. We have succeeded in fabricating the optical gratings on the surface and inside of the diamond plates even though only partial material in the irradiated region phase-transforms from single crystal phase to amorphous phase. The gratings can be used as terahertz polarizers likewise. The modulation depths are 53% at 1.6 THz and 40% at 2.52 THz, which can be further improved by optimizing the fabrication parameters and the fill factors of gratings. We have also fabricated the electric wire on the surface of the normal grade diamond plate.

Chiral properties of the zero-field spiral state and field-induced magnetic phases of the itinerant kagome metal YMn6Sn6

Applying a magnetic field in the hexagonal plane of YMn$_6$Sn$_6$ leads to a complex magnetic phase diagram of commensurate and incommensurate phases, one of which coexists with the topological Hall effect (THE) generated by a unique fluctuation-driven mechanism. Using unpolarized neutron diffraction, we report on the solved magnetic structure for two previously identified, but unknown, commensurate phases. These include a low-temperature, high-field fan-like phase and a room-temperature, low-field canted antiferromagnetic phase. An intermediate incommensurate phase between the fan-like and forced ferromagnetic phases is also identified as the last known phase of the in-plane field-temperature diagram. Additional characterization using synchrotron powder diffraction reveals extremely high-quality, single-phase crystals, which suggests that the presence of two incommensurate magnetic structures throughout much of the phase diagram is an intrinsic property of the system. Interestingly, polarized neutron diffraction shows that the centrosymmetric system hosts preferential chirality in the zero-field double-flat-spiral phase, which, along with the THE, is a topologically non-trivial characteristic.

Mn Katkılı PIN-PMN-PT Tekil Kristalinin Dielektrik Katsayısı, Relaksiyon Zamanı ve Aktivasyon Enerjisinin Hesaplanması

Relaksör-ferroelektrik malzemeler 1950 li yıllarda keşfedilmiştir, birçok uygulamada kullanılmasına rağmen hala bazı mekanik ve elektrik özellikleri tam olarak anlaşılamamıştır. Özellikle ferroelektrik faz geçişlerindeki, mekanik ve elektriksel davranımlarının sıcaklık bağımlılıklarını tam olarak modelleyebilen bir yaklaşım eksikliği vardır. Bu çalışmada, Landau fenomonolojik teori kullanılarak, Mn katkılı PIN-PMN-PT tek kristal karışım malzemenin ferroelektrik rhombohedral-monoklinik faz geçişinde (TC=112 0C) 512 ve 584 cm-1 Raman modları için; kendiliğinden polarizasyon, dielektrik duyarlık ve gevşeme zamanı sıcaklığa bağlı olarak hesaplanmıştır. Landau fenomonolojik teoriden türetilen dielektrik duyarlık bağıntısı, deneysel veriler ile uyumlu sonuçlar vermiştir. Ayrıca, ferroelektrik rhombohedral fazda farklı sıcaklık aralıkları için aktivasyon enerjileri pseuode-spin fonon ve enerji dalgalanma model yaklaşımları kullanılarak hesaplanmıştır. Her iki model kullanılarak hesaplanan sönümleme sabiti değerlerimiz, gözlemlenen verilerle uyumlu çıkmıştır.

Role of Metal-Chloride Anions in Photoluminescence Regulations for Hybrid Metal Halides.

Organic-inorganic hybrid metal halides with emissive organic cations are of great interest due to their structural diversity and interesting photophysical properties. Here, we assemble emissive organic cations (EnrofloH22+) with different metal-chloride anions (Pb2Cl62- to Bi2Cl104- to SnCl62-) to form the new single crystal phases, and thus the photoluminescence properties of the metal halides, including Stokes shift, full width at half-maximum (FWHM), and photoluminescence quantum yield (PLQY) have been studied accordingly. (EnrofloH2)SnCl6·H2O, as an example, possesses narrow FWHM and high PLQY, which are caused by the strong π-π stacking and inter- and intramolecular hydrogen bonds interactions. Compared with EnrofloH22+ cation in solution, the interactions generate a restraining effect and increase the rigid degree of EnrofloH22+ cation in the bulk single crystals. Our work clarifies the photophysical properties of the EnrofloH22+ organic cations by constructing the inter- and intramolecular interactions and boosts the further study of organic-inorganic hybrid metal halides materials with different luminescence mechanisms.

Nematic Phase of Plate-like Semicrystalline Block Copolymer Single Crystals in Solution Studied by Small-Angle X-Ray Scattering.

Crystalline block copolymers have been used to prepare plate-like colloidal systems with well-controlled size, shape, and size distribution. The isotropic-to-nematic (I-N) phase transition of the novel plate-like colloidal particle suspensions has been reported previously. In this work, we focus on the characterization of the solution structure of the crystals and the N-phase using small- and ultrasmall-angle X-ray scattering techniques (SAXS/USAXS). The system has polystyrene-block-poly(l-lactide) (PS-b-PLLA) block copolymer single crystals (BCSCs) with different sizes dispersed in p-xylene. These crystals are truncated lozenge in shape and have effective diameters ranging from 550 to 4000 nm with a uniform dry thickness of 18.0 nm. Scattering of the individual crystal in solution can be simplified using a disc model with a core layer of 9-10 nm due to the lower contrast of the tethered PS layer. BCSC suspensions filled in thin quartz capillaries are prepared for monitoring the structural information. SAXS measurements of the isotropic phase show a strong face-to-face correlation, indicating that platelets form small stacked clusters in solutions. The isotropic phase is thus a coexistence of single crystals and the stacked multiple-layered clusters. The face-to-face spacing, d, in the N phases is around 75-90 nm, which increases slightly upon increasing the size of crystals. For a given system, the spacing does not change with increasing concentration under the current experimental conditions. Finally, the possible formation of lamellar domains within the N phase is also discussed due to the lateral attraction of this system. These results demonstrate the importance of the lateral attraction between the polar crystalline PLLA blocks on the formation of the N phase: the BCSCs self-assemble into larger sheets via the lateral attraction, which further enhances the I-N transition.

Uranyl Phosphonates with Multiple Uranyl Coordination Geometries and Low Temperature Phase Transition

Main observation and conclusionTwo new uranium(VI) phosphonate compounds, namely K8[N(C2H5)4]2(UO2)17(H2O)4[CH2(PO3)2]8[CH2(PO3)(PO3H)]4‧16(H2O) (1) and [N(C2H5)4]4(H3O)2(UO2)10[CH2(PO3)2]5[CH2(PO3)(PO3H)]2‧10H2O (2), have been synthesized under mild hydro/solvothermal condition. The structural analysis of the two compounds reveals that they both contain all three typical coordination geometries of the U(VI) ions, including UO6 tetragonal, UO7 pentagonal, and UO8 hexagonal bipyramids. Moreover, compound 1 displays a temperature‐induced single crystal to single crystal phase transformation as confirmed by the Single‐crystal X‐ray diffraction data collected at different temperatures. Temperature‐dependent fluorescence spectra presented herein illustrate the perturbation of the electronic structure of uranyl centers.

Synthesis of fluorescent terbium-based metal-organic framework for quantitative detection of nitrite and ferric ions in water samples

Through a solvothermal reaction between the corresponding lanthanide(III) nitrate, 1,10 o-phenanthroline and pyridine 3,5-dicarboxylic acid ligands, a novel two-dimensional terbium-based metal-organic framework (Tb-MOF), named {Tb2O0.5(C12H8N2)2(C7H3NO4)3(H2O)2.75}n (1) with strong fluorescence was synthesized by hydrothermal method. The single crystal structure and phase purity of the as-synthesized Tb-MOF were verified by single crystal X-ray diffraction. Subsequently, some studies on the morphology, structure, and optical properties of the compound were carried out. The results show that the synthesized Tb-MOF (1) can be used for the fluorescence sensing of nitrite and ferric ions. Simultaneously, the as-synthesized crystal structure offers good chemical stability in different environments, such as common organic solvents, solutions with a wide pH range, and aqueous solutions of metal ions. Besides, it has good chemical stability in a certain temperature range. In addition, a detection method for nitrite and iron ions was established based on the principle of fluorescence quenching of Tb-MOF by the analytical target, showing good recovery and precision. The proposed method provides a reliable new method for detecting nitrite and ferric ions concentrations in actual water samples.

Transfer learning with graph neural networks for optoelectronic properties of conjugated oligomers.

Despite the remarkable progress of machine learning (ML) techniques in chemistry, modeling the optoelectronic properties of long conjugated oligomers and polymers with ML remains challenging due to the difficulty in obtaining sufficient training data. Here, we use transfer learning to address the data scarcity issue by pre-training graph neural networks using data from short oligomers. With only a few hundred training data, we are able to achieve an average error of about 0.1 eV for the excited-state energy of oligothiophenes against time-dependent density functional theory (TDDFT) calculations. We show that the success of our transfer learning approach relies on the relative locality of low-lying electronic excitations in long conjugated oligomers. Finally, we demonstrate the transferability of our approach by modeling the lowest-lying excited-state energies of poly(3-hexylthiophene) in its single-crystal and solution phases using the transfer learning models trained with the data of gas-phase oligothiophenes. The transfer learning predicted excited-state energy distributions agree quantitatively with TDDFT calculations and capture some important qualitative features observed in experimental absorption spectra.

Three-dimensional topological semimetal phase in layered TaNiTe5 probed by quantum oscillations

Layered three-dimensional (3D) topological semimetals have attracted intensively attention due to the exotic phenomena and abundantly tunable properties. Here we report the experimental evidence for the 3D topological semimetal phase in layered material TaNiTe5 single crystals through quantum oscillations. Strong quantum oscillations have been observed with diamagnetism background in TaNiTe5. By analyzing the de Haas-van Alphen oscillations, multi-periodic oscillations were extracted, in content with magnetotransport measurements. Moreover, nontrivial "{\pi}" Berry phase with 3D Fermi surface is identified, indicating the topologically nontrivial feature in TaNiTe5. Additionally, we demonstrated the thin-layer of TaNiTe5 crystals is highly feasible by the mechanical exfoliation, which offers a platform to explore exotic properties in low dimensional topological semimetal and paves the way for potential applications in nanodevices.

Type-II Dirac points and edge transports in phononic crystal plates

The accidentally degenerate type-II Dirac points in sonic crystal has been realized recently. However, elastic phononic crystals with type-II Dirac points have not yet been explored. In this work, we design a two-dimensional phononic crystal plate in square lattice with type-II Dirac points for elastic waves. The type-II Dirac points, different from the type-I counterparts, have the tiled dispersions and thus the iso-frequency contours become crossed lines. By tuning structures to break the mirror symmetry, the degeneracies of the type-II Dirac points are lifted, leading to a band inversion. In order to have a further explanation, we also calculate the Berry curvatures of phononic crystals with opposite structure parameters, and it turns out that these two crystals hold opposite signs around the valley. The phononic crystal plates before and after the band inversion belong to different topological valley phases, whose direct consequence is that the topologically protected gapless interface states exist between two distinct topological phases. Topologically protected interface states are found by calculating the projected band structures of a supercell that contains two kinds of interfaces between two topological phases. Robustness of the interface transport is verified by comparing the transmission rate for perfect interface with that for defective interface. Moreover, owing to the special stress field distributions of the elastic plate waves, the boundaries of a single phononic crystal phase can similarly host the gapless boundary states, which is found by calculating the projected band structures of a supercell with a single phase, thus having two free boundaries on the edges. This paper extends the two-dimensional Dirac points and valley states in graphene-like systems to the type-II cases, and obtains in the same structure the gapless interface and boundary propagations. Owing to the simple design scheme of the structure, the phononic crystal plates can be fabricated and scaled to a small size. Our system provides a feasible way of constructing high-frequency elastic wave devices.

Reversible single-crystal to single-crystal phase transformation between a new Werner clathrate and its apohost.

In this work, we report the synthesis and structural characterisation of the ligand 2-(pyridin-3-yl)-benzo[de]isoquinoline-1,3(2H)-dione, 5, its isostructural Werner complexes ML4(NCS)2 (L = 5; M = Co(ii) and Ni(ii)), and five clathrates with three aromatic guests, ML4(NCS)2·2G (M = Co(ii) and Ni(ii), G = nitrobenzene (NB); M = Co, G = 1,2-dichlorobenzene (1,2-DCB); M = Co(ii) and Ni(ii), G = o-xylene (OX)). 5 was prepared in high yield by condensation in the solid-state (C3S3, Cocrystal Controlled Solid-State Synthesis). The Werner complexes ML4(NCS)2 (M = Co(ii) and Ni(ii)) (apohosts) were prepared by reacting M(NCS)2 (M = Co(ii) and Ni(ii)) and 5 in 1-butanol at 60 °C for 24 h. The Werner clathrates were prepared by reacting M(NCS)2 (M = Co(ii) and Ni(ii)), G and 5 in 1-butanol at 60 °C for 48–96 h. The clathrates were observed to transform to the apohost ML4(NCS)2 upon heating. CoL4(NCS)2·2NB was subsequently regenerated by exposing CoL4(NCS)2 to liquid NB at 60 °C for 48 h. This phase change occurred as a single-crystal to single-crystal phase transformation and was studied by single crystal X-ray diffraction, powder X-ray diffraction and thermal analyses. Structural analyses of the apohost CoL4(NCS)2 and its Werner clathrate CoL4(NCS)2·2NB indicated that rotational freedom of the Co-N bonds together with torsional flexibility of the ligand between the imide bond and the pyridine moiety are key to enabling the structural switching induced by exposure to NB or its removal.

Effect of nitrogen vacancies on the growth, dislocation structure, and decomposition of single crystal epitaxial (Ti1-xAlx)Ny thin films

The effect of varying nitrogen vacancies on the growth, microstructure, spinodal decomposition and hardness values of predominantly single crystal cubic phase c-(Ti1-xAlx)Ny films was investigated. Epitaxial c-(Ti1−xAlx)Ny films with y = 0.67, 0.79, and 0.92 were grown on MgO(001) and MgO(111) substrates by magnetron sputter deposition. High N vacancy c-(Ti1−xAlx)N0.67 films deposited on MgO(111) contained coherently oriented w-(0001) structures while segregated conical structures were observed on the films grown on MgO(001). High resolution STEM images revealed that the N-deficient growth conditions induced segregation with small compositional fluctuations that increase with the number of N vacancies. Similarly, strain map analysis of the epitaxial c-(Ti1−xAlx)Ny (001) and (111) films show fluctuations in strain concentration that scales with the number of N vacancies and increases during annealing. The spinodal decomposition coarsening rate of the epitaxial c-(Ti1−xAlx)Ny films was observed to increase with decreasing N vacancies. Nanoindentation showed decreasing trends in hardness of the as-deposited films as the N vacancies increase. Isothermal post-anneal at 1100 °C in vacuum for 120 min revealed a continuation in the increase in hardness for the film with the largest number of N vacancies (y = 0.67) while the hardness decreased for the films with y = 0.79 and 0.92. These results suggest that nitrogen-deficient depositions of c-(Ti1-xAlx)Ny films help to promote a self-organized phase segregation, while higher N vacancies generally increase the coherency strain which delays the coarsening process and can influence the hardness at high temperatures.

Correlation of elastic and optoelectronic properties near structural phase transition in organic–inorganic lead iodide perovskite single crystals

The experimental evidence of the influence of the structural phase transition on the elastic and optoelectronic properties of CH3NH3PbI3 single crystals has been reported. A peak in the attenuation for longitudinal and shear ultrasonic waves and a step-like anomaly in their velocity have been found near the structural the orthorhombic-to-tetragonal phase transition (160 K). The narrow hysteresis observed in the temperature dependences of the elastic properties confirms that this is the first-order phase transition. A redshift of the absorption threshold (of about 110 meV) has been revealed both in the photocurrent (PC) and in the photoluminescence (PL) spectra with increasing temperature from 140 to 160 K. In the orthorhombic phase of CH3NH3PbI3 single crystals, the fine exciton structure in the PC spectrum has been found with an exciton binding energy of 19–25 meV. The peculiarities of the PC and PL spectra near the phase transition temperature (160 K) have been observed within a wider temperature range in contrast to the elastic anomalies that can be explained by the complex structure of the near-surface region. It may be essential for the further development of optoelectronic devices based on hybrid halide perovskites.

Preparation of High-Entropy (Zr0.25Hf0.25Ta0.25Ti0.25)C-Ni-Co Composite by Spark Plasma Sintering

In the present work, the thermodynamic formation possibility and stability of high-entropy (Zr0.25Hf0.25Ta0.25Ti0.25)C ceramic single phase were theoretically calculated by first principles, and a novel (Zr0.25Hf0.25Ta0.25Ti0.25)C high-entropy ceramic-Ni-Co composite was successfully prepared by spark plasma sintering (SPS). The first principles calculation indicated the atomic size difference δ for (Zr0.25Hf0.25Ta0.25Ti0.25)C was 3.23 pct, which was < 6.6 pct, and solid solution would possibly happen. The calculated DFT formation enthalpy of the (Zr0.25Hf0.25Ta0.25Ti0.25)C system was − 1.78 eV. The negative formation enthalpy indicated that (Zr0.25Hf0.25Ta0.25Ti0.25)C was thermodynamically stable. The experimental results showed a new fcc (Fm-3m) single rock salt crystal structure ceramic phase was formed after SPS sintering. Two phases (ceramic phase and metal phase) were presented in the material. Besides, for the (Zr0.25Hf0.25Ta0.25Ti0.25)C phase, the Hf, Ta, Zr and Ti distributed uniformly, and no secondary phase was detected. The metal phase was homogeneous along the ceramic phase. No pores and gaps existed between the ceramic phase and metal phase. Good bonding was obtained, caused by some Hf, Ta, Zr or Ti atoms diffusing in the metal phase. The fracture toughness and hardness of the high-entropy (Zr0.25Hf0.25Ta0.25Ti0.25)C ceramic–metal composite were 14.2 MPa m1/2 and 1620 HV(30). The excellent comprehensive performance was caused by good bonding between the ceramic phase and metal phase and mass disorder in the (Zr0.25Hf0.25Ta0.25Ti0.25)C phase.

Fabrication of strontium-substituted hydroxyapatite scaffolds using 3D printing for enhanced bone regeneration

The use of porous three-dimensional (3D) bioceramic scaffolds to facilitate the regeneration of bone defects has attracted great attention because their structures closely mimic the natural extracellular matrix. 3D printing is a versatile method for the fabrication of 3D scaffolds. In this study, 3D strontium-substituted hydroxyapatite (Sr-HA) bioceramic scaffolds were prepared by simple precipitation and 3D printing method. The resulting scaffolds exhibited interconnected microporous structures of strands and a single-phase crystal due to HA, meaning that no changes in the phase composition and microstructure of the scaffolds with the Sr content were observed. However, their dissolution rate and biological performance were substantially influenced by changes in the Sr content of the scaffolds. The optimal Sr content in the Sr-HA scaffolds for enhanced proliferation and differentiation of cells were identified by comparing four compositions of the Sr-HA scaffolds. The results of in vitro bioactivity tests demonstrated that the Sr5-HA scaffold with 0.05 of Sr/(Ca + Sr) molar ratio promoted more rapid cell proliferation, osteogenic differentiation, and cellular mineralization compared with the other scaffolds. Therefore, Sr-HA scaffolds have the potential for application in bone regeneration as new bone graft substitutes.

Water Molecule-Induced Reversible Magnetic Switching in a Bis-Terpyridine Cobalt(II) Complex Exhibiting Coexistence of Spin Crossover and Orbital Transition Behaviors.

The development of molecule-based switchable materials remains an important challenge in the field of molecular science. Achievement of a structural phase transition induced by adsorption/desorption of guest molecules in spin crossover (SCO) Co(II) compounds is of significant interest because of the possibility that the spin state of the magnetic anisotropic high-spin (HS, S = 3/2) and low-spin (LS, S = 1/2) states can be switched via the induced changes in associated intermolecular interactions. In this study, we demonstrated a reversible magnetic switching associated with spin state conversion, along with a single-crystal to single-crystal (SCSC) phase transition induced by dehydration/rehydration. [Co(terpy)2](BF4)2·H2O (1·H2O; terpy = 2,2':6',2''-terpyridine) assembles in the solid state via π-π and CH-π interactions involving adjacent terpyridine cores along the ab direction to form two-dimensional (2D) layered domains. 1·H2O exhibits gradual and incomplete SCO, from fully HS to ca. 0.5 HS, and the field-induced single-molecule magnet (SMM) behavior attributed to the presence of the anisotropic partial high-spin Co(II) species. 1·H2O undergoes a SCSC transformation accompanied by a change from the tetragonal space group I41/a to P42/n via a dehydration process. Dehydrated 1 exhibits a reverse thermal hysteresis behavior (T1/2↑ = 287 K; T1/2↓ = 270 K) in the gradual SCO region from fully HS to ca. 0.5 HS, followed by an ordinary thermal hysteresis (T'1/2↑ = 195 K; T'1/2↓ = 155 K) to fully LS Co(II). A temperature-dependent single-crystal X-ray structural analysis revealed that the reverse hysteresis can be attributed to an order/disorder structural phase transition of the BF4- anions involving a symmetry breaking to yield the monoclinic space group P21/n and orbital (angular momentum) transition (LT). Both the SCSC phase transition and magnetic behavior are switchable by dehydration/rehydration processes; thus 1 again adsorbs water at room temperature to give both the original structure and its magnetic behavior.

The retention at ambient of the high-pressure-induced metastable superconducting phases in antimony single crystals

We have investigated, resistively, non-superconducting single-crystalline antimony and detected several structural transitions under pressures up to 63 GPa. Superconductivity associated with the m-HGL phase with a superconducting transition temperature (Tc) of 3.4 K above ~ 9 GPa and the bcc phase with a Tc of 4.0 K above ~ 30 GPa have been successfully retained up to 135 K and 110 K, respectively, upon the complete and rapid removal of pressure at 77 K. The observations offer a possible path to retain at ambient the pressure-induced metastable superconducting phase in HgBa2Ca2Cu3O8+δ with a Tc of 164 K under ~31 GPa and in LaH10 with a Tc of ~260 K under ~200 GPa, which would make their applications practical by removing the serious high-pressure constraint. The same is also true for superconducting topological devices using antimony.

Applying Configurational Complexity to the 2D Ruddlesden–Popper Crystal Structure

The layered Ruddlesden-Popper crystal structure can host a broad range of functionally important behaviors. Here we establish extraordinary configurational disorder in a layered Ruddlesden-Popper (RP) structure using entropy stabilization assisted synthesis. A protype A2CuO4 RP cuprate oxide with five cations on the A-site sublattice is designed and fabricated into epitaxial single crystal films using pulsed laser deposition. When grown on a near lattice matched substrate, the (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)2CuO4 film features a T'-type RP structure with uniform A-site cation mixing and square-planar CuO4 units. These observations are made with a range of combined characterizations using X-ray diffraction, atomic-resolution scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray absorption spectroscopy measurements. It is further found that heteroepitaxial strain plays an important role in crystal phase formation during synthesis. Compressive strain over ∼1.5% results in the formation of a non-RP cubic phase consistent with a CuX2O4 spinel structure. The ability to manipulate configurational complexity and move between 2D layered RP and 3D cubic crystal structures in cuprate and related materials promises to enable flexible design strategies for a range of functionalities, such as magnetoresistance, unconventional superconductivity, ferroelectricity, catalysis, and ion transport.

High-Strength Behavior of the Al0.3CoCrFeNi High-Entropy Alloy Single Crystals

The main disadvantage of fcc (face-centred cubic lattice) high-entropy alloys is the low stress level at the yield point (σ0.1) at a test temperature above room temperature. This restricts their practical application at high test temperatures from 773 K to 973 K. In this study, we found that a high stress level was reached at the yield point σ0.1 ≈ G/100–G/160 (G is the shear modulus) of the [001]- and [1¯44]-oriented crystals of the Co23.36Cr23.29Fe23.80Ni21.88Al7.67 (Al0.3CoCrFeNi) high-entropy alloy (HEA) within a wide temperature range of 77–973 K under tension, due to the occurrence, of nanotwins, multipoles, dislocations under plastic deformation at 77 K and the subsequent precipitation of ordered L12 and B2 particles. It was shown that grain boundaries are not formed and the samples remain in a single-crystal state after low-temperature deformation and subsequent ageing at 893 K for 50 h. Achieving a high-strength state in the Al0.3CoCrFeNi HEA single crystals induces the orientation dependence of the critical resolved shear stresses (τcr) at T ≥ 200 K (τcr[1¯44] &gt; τcr[001]), which is absent in the initial single-phase crystals, weakens the temperature dependence of σ0.1 above 573 K, and reduces plasticity to 5–13% in the [1¯44] orientation and 15–20% in the [001] orientation.

Elasticity of single-crystal NaCl under high-pressure: simultaneous measurement of x-ray inelastic scattering and diffraction

ABSTRACT Elastic stiffness constants, C ijs, of single crystal of NaCl B1 phase have been determined at pressure up to 20 GPa using inelastic x-ray scattering to measure elastic wave velocities and x-ray diffraction to measure densities in the same experimental setup. The Voigt-Reuss-Hill average velocities calculated from the present Cijs are in good agreement with previous ultrasonic measurements of polycrystalline samples. Absolute pressures based on the present elastic constants and densities are proposed. In order to fit our results an equation of state with at least three parameters (an addition to a reference volume), such as the fourth-order form of Birch–Murnaghan equation or the higher order form of Vinet equation, is required, as fewer parameters do not reproduce the observed pressure dependence of the volume and bulk modulus.