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Infrared bound states in the continuum: random forest method. OPTICS LETTERS 2023; 48:4460-4463. [PMID: 37656528 DOI: 10.1364/ol.494629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 07/31/2023] [Indexed: 09/03/2023]
Abstract
In this Letter, we consider optical bound states in the continuum (BICs) in the infrared range supported by an all-dielectric metasurface in the form of subwavelength dielectric grating. We apply the random forest machine learning method to predict the frequency of the BICs as dependent on the optical and geometric parameters of the metasurface. It is found that the machine learning approach outperforms the standard least square method at the size of the dataset of ≈4000 specimens. It is shown that the random forest approach can be applied for predicting the subband in the infrared spectrum into which the BIC falls. The important feature parameters that affect the BIC wavelength are identified.
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Heat Capacity and Thermodynamic Properties of Germanates CaR2Ge3O10 (R = Pr, Nd) in the Region of 320–1000 K. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2022. [DOI: 10.1134/s0036024422050077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Synthesis, Crystal Structure, and Thermodynamic Properties of CuSm2Ge2O8. RUSS J INORG CHEM+ 2021. [DOI: 10.1134/s0036023621120020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Synthesis, Crystal Structure, and the Optical and Thermodynamic Properties of PrAlGe2O7. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2021. [DOI: 10.1134/s0036024421080124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Crystal Structure and Thermodynamic Properties of Titanate ErGaTi2O7. RUSS J INORG CHEM+ 2021. [DOI: 10.1134/s0036023621040082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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CRYSTAL STRUCTURE OF NORFLOXACINIUM AND 2,2′-BIPYRIDYL-1′-IUM 2-THIOBARBITURATES. J STRUCT CHEM+ 2020. [DOI: 10.1134/s0022476620100170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Characterization of the iron oxide phases formed during the synthesis of core-shell Fe xO y@C nanoparticles modified with Ag. NANOTECHNOLOGY 2020; 31:395703. [PMID: 32516763 DOI: 10.1088/1361-6528/ab9af2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Core-shell FexOy@C nanoparticles (NPs) modified with Ag were studied with x-ray diffraction, transmission electron microscopy, energy dispersive elemental mapping, Mössbauer spectroscopy, static magnetic measurements, and optical magnetic circular dichroism (MCD). FexOy@C NPs synthesized by the pyrolysis process of the mixture of Fe(NO3)3 · 9H2O with oleylamine and oleic acid were added to a heated mixture of oleylamine and AgNO3 in different concentrations. The final product was a mixture of iron oxide crystalline NPs in an amorphous carbon shell and Ag crystalline NPs. The iron oxide NPs were presented by two magnetic phases with extremely close crystal structures: Fe3O4 and γ-Fe2O3. Ag is shown to form crystalline NPs located very close to the iron oxide NPs. An assumption is made about the formation of hybrid FexOy@C-Ag NPs. Correlations were obtained between the Ag concentration in the fabricated samples, their magnetic properties and the MCD spectrum shape. Introducing Ag led to a approximately linear decrease of the NPs saturation magnetization depending upon the Ag concentration, it also resulted into the MCD spectrum shift to the lower light wave energies. MCD was also studied for the Fe3O4@C NPs synthesized earlier with the same one-step process using different heat treatment temperatures, and MCD spectra were compared for two series of NPs. A possible contribution of the surface plasmon excitation in Ag NPs to the MCD spectrum of the FexOy@C-Ag NPs is discussed.
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Monoclinic SmAl 3(BO 3) 4: synthesis, structural and spectroscopic properties. ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2020; 76:654-660. [PMID: 32831284 DOI: 10.1107/s2052520620008781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
Single crystals of SmAl3(BO3)4 were synthesized by the group growth on seeds method. The crystal structure was solved using a single-crystal experiment and the purity of the bulk material was proved by the Rietveld method. This borate crystallizes in the monoclinic C2/c space group with unit-cell parameters a = 7.2386 (3), b = 9.3412 (5), c = 11.1013 (4) Å and β = 103.2240 (10)°. IR and Raman spectroscopic analyses confirmed the monoclinic structure of SmAl3(BO3)4. Under 532.1 nm excitation, luminescence spectra exhibit bands assignable to the transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2. The similarity of the luminescence spectra of the trigonal and monoclinic polymorphs is explained by the minor role of Sm-O bond distortion and the primary role of rotational distortion of SmO6 octahedra. The smaller covalency of the Sm-O bond in alumoborates is deduced in comparison with galloborates. Calorimetric measurements did not reveal high-temperature structural phase transitions up to a temperature of 720 K.
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Hydrates of Lanthanide(III) 2-Thiobarbiturates: Synthesis, Structure, and Thermal Decomposition. RUSS J INORG CHEM+ 2020. [DOI: 10.1134/s0036023620070098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Phenomenological Rule from Correlations of Conduction/Valence Band Energies and Bandgap Energies in Semiconductor Photocatalysts: Calcium Bismuthates versus Strontium Bismuthates. ChemCatChem 2020. [DOI: 10.1002/cctc.201902236] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Synthesis of Samarium OxysulfateSm 2O 2SO 4 in the High-Temperature Oxidation Reaction and Its Structural, Thermal and Luminescent Properties. Molecules 2020; 25:molecules25061330. [PMID: 32183320 PMCID: PMC7144115 DOI: 10.3390/molecules25061330] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 03/10/2020] [Accepted: 03/10/2020] [Indexed: 12/03/2022] Open
Abstract
The oxidation process of samariumoxysulfide was studied in the temperature range of 500–1000 °C. Our DTA investigation allowed for establishing the main thermodynamic (∆Hºexp = −654.6 kJ/mol) and kinetic characteristics of the process (Ea = 244 kJ/mol, A = 2 × 1010). The enthalpy value of samarium oxysulfate (ΔHºf (Sm2O2SO4(monocl)) = −2294.0 kJ/mol) formation was calculated. The calculated process enthalpy value coincides with the value determined in the experiment. It was established that samarium oxysulfate crystallizes in the monoclinic symmetry class and its crystal structure belongs to space group C2/c with unit cell parameters a = 13.7442 (2), b = 4.20178 (4) and c = 8.16711 (8)Å, β = 107.224 (1)°, V = 450.498 (9)Å3, Z = 4. The main elements of the crystalline structure are obtained and the cation coordination environment is analyzed in detail. Vibrational spectroscopy methods confirmed the structural model adequacy. The Sm2O2SO4luminescence spectra exhibit three main bands easily assignable to the transitions from 4G5/2 state to 6H5/2, 6H7/2, and 6H9/2 multiplets.
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Structure and Thermal Decomposition of Nd(III), Gd(III) and Tb(III) 2-Thiobarbiturates. RUSS J INORG CHEM+ 2019. [DOI: 10.1134/s0036023619090134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Structure of Barbituratobis(2,2'-Dipyridyl)copper(II) Heptahydrate. RUSS J COORD CHEM+ 2019. [DOI: 10.1134/s1070328419080037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Negative thermal expansion and electronic structure variation of chalcopyrite type LiGaTe2. RSC Adv 2018; 8:9946-9955. [PMID: 35540803 PMCID: PMC9078859 DOI: 10.1039/c8ra01079j] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 03/05/2018] [Indexed: 11/21/2022] Open
Abstract
The LiGaTe2 crystals were grown by the Bridgman–Stockbarger technique and the cell parameter dependence on temperature in the range of 303–563 K was evaluated by the X-ray diffraction analysis and first principles calculations.
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Crystal structure and properties of polymeric hexaaqua-hexakis-(2-thiobarbiturato)-disamarium(III). J STRUCT CHEM+ 2017. [DOI: 10.1134/s0022476617030155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
Single crystals of (NH4)3SiF7 were studied by the methods of polarization optics, X-ray diffraction and calorimetry.
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Crystal structure and some properties of europium(III) Catena-{tris(1,3-diethyl-2-thiobarbiturate)}. J STRUCT CHEM+ 2016. [DOI: 10.1134/s0022476616010200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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A non-typical sequence of phase transitions in (NH4)3GeF7: optical and structural characterization. Dalton Trans 2016; 45:5321-7. [PMID: 26903439 DOI: 10.1039/c5dt04907e] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Single crystals of germanium double salt (NH4)3GeF7 = (NH4)2GeF6·NH4F = (NH4)3[GeF6]F were grown and studied by the methods of polarization optics and X-ray diffraction. The birefringence Δn = (no - ne), the rotation angle of the optical indicatrix ϕ(T) and unit cell parameters were measured in the temperature range 100-400 K. Three structural phase transitions were found at the temperatures: T1↓ = 279.2 K (T1↑ = 279.4 K), T2↑ = 270 K (T2↓ = 268.9 K), T3↓ = 218 K (T3↑ = 227 K). An unusual sequence of symmetry transformations with temperature change was established: P4/mbm (Z = 2) (G1) ↔ Pbam (Z = 4) (G2) ↔ P21/c (Z = 4) (G3) ↔ Pa3[combining macron] (Z = 8) (G4). The crystal structures of different phases were determined. The experimental data were additionally interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account the critical and noncritical atomic displacements. Strengthening of the N-HF hydrogen bonds can be a driving force of the observed phase transitions.
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Abstract
Microcrystals of orthorhombic rubidium samarium molybdate, β-RbSm(MoO4)2, have been fabricated by solid state synthesis at T = 450 °C, 70 h, and at T = 600 °C, 150 h.
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Oxatrane is a parent compound of a new atrane family: Crystal and molecular structure of triethanolamine N-oxide. DOKLADY CHEMISTRY 2014. [DOI: 10.1134/s0012500814090031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Structures of bis(2-thiobarbiturato-O)tetraaquamagnesium and catena-[(μ2-2-thiobarbiturato-O,O)(2-thiobarbiturato-O) bis(μ2-aqua)diaquastrontium] monohydrate. RUSS J INORG CHEM+ 2014. [DOI: 10.1134/s0036023614020107] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Magnetic phase diagram of the olivine-type Mn2GeO4 single crystal estimated from magnetic, resonance and thermodynamic properties. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:136003. [PMID: 23462522 DOI: 10.1088/0953-8984/25/13/136003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Mn2GeO4 single crystals with the olivine structure grown by the modified flux method have been investigated. Pronounced magnetic phase transitions at T1 = 47.7 K, T2 = 17 K and T3 = 5.5 K, with T2 being dependent on an applied magnetic field, have been found. Based on the data of magnetic, resonance and temperature measurements, the entire phase diagram of Mn2GeO4 has been built. Mn2GeO4 is shown to be a material with a complex magnetic structure consisting of two magnetic subsystems.
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Synthesis, crystal structure, and magnetic properties of a Li8FeSm22O38 single crystal. CRYSTALLOGR REP+ 2013. [DOI: 10.1134/s1063774512060065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Electronic structure of α-SrB4O7: experiment and theory. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:085503. [PMID: 23344015 DOI: 10.1088/0953-8984/25/8/085503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The investigation of valence band structure and electronic parameters of constituent element core levels of α-SrB(4)O(7) has been carried out with x-ray photoemission spectroscopy. Optical-quality crystal α-SrB(4)O(7) has been grown by the Czochralski method. Detailed photoemission spectra of the element core levels have been recorded from the powder sample under excitation by nonmonochromatic Al Kα radiation (1486.6 eV). The band structure of α-SrB(4)O(7) has been calculated by ab initio methods and compared to XPS measurements. It has been found that the band structure of α-SrB(4)O(7) is weakly dependent on the Sr-related states.
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Powder diffraction crystal structure analysis using derivative difference minimization: example of the potassium salt of 1-(tetrazol-5-yl)-2-nitroguanidine. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 2005; 61:435-42. [PMID: 16041093 DOI: 10.1107/s0108768105015004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2005] [Accepted: 05/10/2005] [Indexed: 11/10/2022]
Abstract
The crystal structure of the potassium salt of 1-(tetrazol-5-yl)-2-nitroguanidine [K(C2H3N8O2)] was solved and refined from X-ray powder diffraction data by applying the derivative difference minimization (DDM) method. The compound is of interest as an energetic substance. The structure model was found from a Patterson search. The reflection intensities for the Patterson synthesis were derived from the powder profile by applying a newly developed DDM-based profile decomposition procedure. The use of the DDM method allowed successful location and unconstrained refinement of all the atomic positions, including those of three independent H atoms. The advantages of DDM in terms of the precision and reproducibility of the structural parameters are discussed in comparison to Rietveld refinement results. The failure to refine the H-atom positions by the Rietveld method was attributed to systematic errors associated with the background modelling, which are avoided by DDM.
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Crystal and molecular structure of nitraminotetrazole and nitramino-1,2,4-triazole. IV. 5-nitraminotetrazole sodium salt sesquihydrate. J STRUCT CHEM+ 2004. [DOI: 10.1007/s10947-005-0026-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Crystal and Molecular Structure of the Nitramino Derivatives of Tetrazole and 1,2,4-Triazole. III. 5-Nitraminotetrazole Lithium Salt Monohydrate. J STRUCT CHEM+ 2004. [DOI: 10.1023/b:jory.0000048894.84780.cd] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Crystal and Molecular Structure of Nitramino Derivatives of Tetrazole and 1,2,4-Triazole. II. 5-Nitraminotetrazole Diammonium Salt. J STRUCT CHEM+ 2004. [DOI: 10.1023/b:jory.0000041520.90323.fe] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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