Isotropic Negative Area Compressibility over Large Pressure Range in Potassium Beryllium Fluoroborate and its Potential Applications in Deep Ultraviolet Region
Abstract:Isotropic negative area compressibility, which is very rare, is observed in KBBF and the related mechanism is investigated by combined high-pressure X-ray diffraction (XRD) experiments and first-principles calculations. The strong mechanical anisotropy leads to a large Poisson's ratio and high figure of merit for the acoustic-optics effect, giving KBBF potential applications as smart strain converters and deep-ultraviolet (DUV) acoustic-optic devices.
“…The derived compression coefficients along the a and c directions are σ a = 5.2(8) × 10 −4 /GPa (AP to 3 GPa), σ a = −5.0(6) × 10 −4 /GPa (3 to 10 GPa) and σ c = 1.9(2) × 10 −2 /GPa (AP to 10 GPa). These values agree very well with what has been reported earlier 6 . Such large anisotropic compression, σ c = 38 × σ a , is a direct reflection of the intrinsic anisotropic structural bonding property.…”
Section: Resultssupporting
confidence: 93%
“…This indicates the strong anisotropic response to pressure. However there is no evidence showing any phase transition over the pressure range covered here, consistent with a previous report 6 .Figure 2The pressure-dependent XRD patterns show the dramatic changes of the (006) reflection (green arrow) with pressure, in contrast with the (018) reflection (red arrow) in the 2θ range from 10° to 16° for hydro-KBBF.
…”
Section: Resultssupporting
confidence: 91%
“…We will come back to discuss this unusual pressure dependence later. The pressure range showing a NAC effect (in the ab plane) is from 3 GPa to 10 GPa, in contrast to the previous observation showing the effect from 0.22 GPa to 6.39 GPa 6 .Figure 3The pressure dependences of the lattice parameters a , c , and the volumes V of the R32 and the KBBF are shown in ( a , b , c and d ), respectively. The green lines in ( c ) and ( d ) represent the best fit of the second-order Birch-Murnaghan equation of state for R32 and , respectively.
…”
Section: Resultsmentioning
confidence: 77%
“…The growth temperatures varied from 730 °C to 800 °C at different stages in the process. Hydro-KBBF single crystals were grown in aqueous solutions of KF and H 3 BO 3 with seeds obtained through spontaneous nucleation 6 . The growth temperature was 360 °C and the filling rate of the autoclave was about 80%, resulting in a pressure of about 120 MPa.…”
Section: Methodsmentioning
confidence: 99%
“…For example, a deep-UV laser generated from single-crystalline KBBF made possible measurement of the energy gap and its dependence on electron propagation directions in unconventional superconductors, realized from correlated d - and f -electrons 1, 3, 4 . In addition to the unique non-linear optical properties, other new properties of KBBF crystal like negative thermal expansion (NTE), negative area compressibility (NAC), and the associated potential applications such as smart strain conversion and acoustical-optical coupling devices have been explored recently 5, 6 . These abnormal behaviors are believed to be attributed to the concerted structural distortion of the [BeO 3 F] tetrahedra in the two-dimensional [Be 2 BO 3 F 2 ] framework under external stimulus of temperature and/or pressure 6 .…”
Strong anisotropic compression with pressure on the remarkable non-linear optical material KBe2BO3F2 has been observed with the linear compression coefficient along the c axis found to be about 40 times larger than that along the a axis. An unusual non-monotonic pressure response was observed for the a lattice parameter. The derived bulk modulus of 31 ± 1 GPa indicates that KBe2BO3F2 is a very soft oxide material yet with stable structure up to 45 GPa. A combination of high-pressure synchrotron powder X-ray diffraction, high-pressure Raman spectroscopy, and Density Functional Theory calculations points to the mechanism for the unusual pressure response being due to the competition between the K-F bond length and K-F-K bond angle and the coupling between the stretching and twisting vibration modes.
“…The derived compression coefficients along the a and c directions are σ a = 5.2(8) × 10 −4 /GPa (AP to 3 GPa), σ a = −5.0(6) × 10 −4 /GPa (3 to 10 GPa) and σ c = 1.9(2) × 10 −2 /GPa (AP to 10 GPa). These values agree very well with what has been reported earlier 6 . Such large anisotropic compression, σ c = 38 × σ a , is a direct reflection of the intrinsic anisotropic structural bonding property.…”
Section: Resultssupporting
confidence: 93%
“…This indicates the strong anisotropic response to pressure. However there is no evidence showing any phase transition over the pressure range covered here, consistent with a previous report 6 .Figure 2The pressure-dependent XRD patterns show the dramatic changes of the (006) reflection (green arrow) with pressure, in contrast with the (018) reflection (red arrow) in the 2θ range from 10° to 16° for hydro-KBBF.
…”
Section: Resultssupporting
confidence: 91%
“…We will come back to discuss this unusual pressure dependence later. The pressure range showing a NAC effect (in the ab plane) is from 3 GPa to 10 GPa, in contrast to the previous observation showing the effect from 0.22 GPa to 6.39 GPa 6 .Figure 3The pressure dependences of the lattice parameters a , c , and the volumes V of the R32 and the KBBF are shown in ( a , b , c and d ), respectively. The green lines in ( c ) and ( d ) represent the best fit of the second-order Birch-Murnaghan equation of state for R32 and , respectively.
…”
Section: Resultsmentioning
confidence: 77%
“…The growth temperatures varied from 730 °C to 800 °C at different stages in the process. Hydro-KBBF single crystals were grown in aqueous solutions of KF and H 3 BO 3 with seeds obtained through spontaneous nucleation 6 . The growth temperature was 360 °C and the filling rate of the autoclave was about 80%, resulting in a pressure of about 120 MPa.…”
Section: Methodsmentioning
confidence: 99%
“…For example, a deep-UV laser generated from single-crystalline KBBF made possible measurement of the energy gap and its dependence on electron propagation directions in unconventional superconductors, realized from correlated d - and f -electrons 1, 3, 4 . In addition to the unique non-linear optical properties, other new properties of KBBF crystal like negative thermal expansion (NTE), negative area compressibility (NAC), and the associated potential applications such as smart strain conversion and acoustical-optical coupling devices have been explored recently 5, 6 . These abnormal behaviors are believed to be attributed to the concerted structural distortion of the [BeO 3 F] tetrahedra in the two-dimensional [Be 2 BO 3 F 2 ] framework under external stimulus of temperature and/or pressure 6 .…”
Strong anisotropic compression with pressure on the remarkable non-linear optical material KBe2BO3F2 has been observed with the linear compression coefficient along the c axis found to be about 40 times larger than that along the a axis. An unusual non-monotonic pressure response was observed for the a lattice parameter. The derived bulk modulus of 31 ± 1 GPa indicates that KBe2BO3F2 is a very soft oxide material yet with stable structure up to 45 GPa. A combination of high-pressure synchrotron powder X-ray diffraction, high-pressure Raman spectroscopy, and Density Functional Theory calculations points to the mechanism for the unusual pressure response being due to the competition between the K-F bond length and K-F-K bond angle and the coupling between the stretching and twisting vibration modes.
Design and exploratory synthesis of new mid-infrared (mid-IR) nonlinear optical (NLO) materials are urgently needed for modern laser science and technology because the widely used IR NLO crystals still suffer from their inextricable drawbacks. Herein, a multi-level data-driven approach to realize fast and efficient structure prediction for the exploration of promising mid-IR NLO materials is proposed. Techniques based on machine learning, crystal structure prediction, high-throughput calculation and screening, database building, and experimental verification are tightly combined for creating pathways from chemical compositions, crystal structures to rational synthesis. Through this data-driven approach, not only are all known structures successfully predicted but also five thermodynamically stable and 50 metastable new selenides in A I B III Se 2 systems (A I = Li, Na, K, Rb, and Cs; B III = Al and Ga) are found, among which eight outstanding compounds with wide bandgaps (> 2.70 eV) and large SHG responses (>10 pm V −1 ) are suggested. Moreover, the predicted compounds I42d-LiGaSe 2 and I4/mcm-KAlSe 2 are successfully obtained experimentally. In particular, LiGaSe 2 exhibits a robust SHG response (≈2 × AGS) and long IR absorption edge that can cover two atmospheric windows (3-5, 8-12 µm). Simultaneously, this new research paradigm is also applicative for discovering new materials in other fields.
Materials with negative Poisson's ratio attract considerable attention due to their underlying intriguing physical properties and numerous promising applications, particularly in stringent environments such as aerospace and defense areas, because of their unconventional mechanical enhancements. Recent progress in materials with a negative Poisson's ratio are reviewed here, with the current state of research regarding both theory and experiment. The inter-relationship between the underlying structure and a negative Poisson's ratio is discussed in functional materials, including macroscopic bulk, low-dimensional nanoscale particles, films, sheets, or tubes. The coexistence and correlations with other negative indexes (such as negative compressibility and negative thermal expansion) are also addressed. Finally, open questions and future research opportunities are proposed for functional materials with negative Poisson's ratios.
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