R3 Space Research Articles

Bulk photovoltaic effect and high mobility in the polar 2D semiconductor SnP2Se6.

The growth of layered 2D compounds is a key ingredient in finding new phenomena in quantum materials, optoelectronics, and energy conversion. Here, we report SnP2Se6, a van der Waals chiral (R3 space group) semiconductor with an indirect bandgap of 1.36 to 1.41 electron volts. Exfoliated SnP2Se6 flakes are integrated into high-performance field-effect transistors with electron mobilities >100 cm2/Vs and on/off ratios >106 at room temperature. Upon excitation at a wavelength of 515.6 nanometer, SnP2Se6 phototransistors show high gain (>4 × 104) at low intensity (≈10-6 W/cm2) and fast photoresponse (< 5 microsecond) with concurrent gain of ≈52.9 at high intensity (≈56.6 mW/cm2) at a gate voltage of 60 V across 300-nm-thick SiO2 dielectric layer. The combination of high carrier mobility and the non-centrosymmetric crystal structure results in a strong intrinsic bulk photovoltaic effect; under local excitation at normal incidence at 532 nm, short circuit currents exceed 8 mA/cm2 at 20.6 W/cm2.

Sextuplet luminescence with dynamically variable color/brightness in chromium activated gallium-silicate solid solution in R3 space group

The development of dynamic multi-color luminescence is a tremendous challenge for anti-counterfeiting. Herein, we have successfully synthesized Cr3+ activated gallium-silicate base material systems as the effective luminescent materials responsive to multiple field stimulation, exhibiting sextuplet luminescence including photoluminescence, strong red persistent luminescence (PersL), photo/thermo stimulated luminescence (PSL/TSL), photo-stimulated PersL and up-conversion luminescence (UCL). The luminescence quenching temperature is also improved in Cr3+,Yb3+,Er3+ co-doping sample relatives to Cr3+ single-doping phosphor. Especially, when Er3+ and Yb3+ are co-doped into Cr3+ activated phosphor system, UV preirradiated phosphor not only demonstrates an additional UCL from Er3+ ions accompanied with red PSL from the Cr3+ under NIR laser irradiation, but also leads to a dynamic change in color/brightness under the extension of NIR laser irradiation time. The multimode luminescence mechanisms are also proposed. Based on excellent luminescence characteristics, multi-color and multi-mode anti-counterfeiting patterns have been designed, especially appearing of dynamic anti-counterfeiting on luminescent color/brightness, which provides new dimensions for anti-counterfeiting technologies.

Structural stability and polarization analysis of rhombohedral phases of HfO2

Since the experimental observation of a rhombohedral phase of hafnium oxide, there remains controversy over whether this phase belongs to the R3 or R3m space group. Moreover, the origin of polarization in these two rhombohedral phases has not been comparatively elucidated. Here, we present a theoretical study comparing the relative stability and ferroelectricity of the R3 and R3m phases of HfO2, representing two potential forms of heavily Zr-doped ferroelectric thin films of hafnia found recently. We comprehensively investigate their structural stability and polarization response under in-plane compressive strain. A phase transition from R3 to R3m is discovered under biaxial compressive strain. The direction and magnitude of polarization in both phases can be tuned by strain. Through symmetry mode analysis, we elucidate the improper nature of ferroelectricity. These findings may advance understanding of ferroelectricity in hafnia thin films.

Vector assessment model in R3 space for forest value

While Forests have enormous potential and value, it is necessary to establish a valuation model to help us make decisions and make sound recommendations. To this end, I have made the following contributions. I collected nine data sets from 12 forests and integrated them into three dimensions. I combined the subjective hierarchical analysis (AHP) and CRITIC objective assignment method to obtain the weights. Using the indicators and data of these three dimensions, I constructed a vector assessment model in R3 space, where the modal length of the spatial vector represents the forest value, the angle with the standard vector (1, 1, 1) represents the space of progress, and the plane established by the two vectors together represents the direction of improvement. In addition, I found a relationship between artificial logging intensity and forest value, and established extreme value points, concluding that appropriate artificial logging helps to improve forest value. Because the modal length of Siberian coniferous forests is 1.008 and the angle of 13 degrees, there is a lot of room for improvement, and I analysed this further. I used the GM (1,1) model to predict the carbon sequestration data of Siberian coniferous forests, and the results are consistent with the analysis results of the three-dimensional vector model I established.

Structural analysis and properties of two novel pharmaceutical salts of letermovir

Two novel pharmaceutical salts of letermovir (LM) were successfully achieved by a slow reaction in solution containing LM with ethylenediamine (EDA) and diisopropylamine (DIPA). In this article, crystal structure, X-ray diffraction, thermal properties, 1H NMR, 13C NMR, HPLC analysis, stability and solubility of salt 1 and salt 2 have been discussed. Salt 1 crystalized in R3 space group and salt 2 crystalized in P3221 space group. The formation of salt was proved by pKa rule and single crystal determination. From the perspective of crystal structure, for salt 1 and salt 2, the strong hydrogen bond makes the crystal structure more stable. The weak interaction between molecules is further studied by Hirshfeld surface and 2D-fingerprint plots. Notably, this is the first report of a single crystal structure of LM, which could contribute to the development of corresponding drugs. In addition, salt 1 and salt 2 showed better solubility and stability under wet conditions, and had the potential to replace the bulk drug.

Electronic and optical properties of the R3 Ni3TeO6 compound described by the modified Becke-Johnson exchange potential

Calculations based on the density functional theory (DFT) have been realized to study the electronic and optical properties of the Ni3TeO6 compound with a hexagonal crystal structure (R3 space group). Exchange and correlation electronic effects were described by a modified Becke-Johnson (mBJ) potential in its semiconductor variance form. The collinear antiferromagnetic state of the R3 Ni3TeO6 compound was simulated. The calculated spin magnetic moment of the Ni atoms (1.65 μB) was found to be in good agreement with the experimental result (2.03 μB). Moreover, the calculated optical band gap (2.8 eV) agreed well with the experimental prediction (2.5 eV). These facts suggest a reliable electronic structure description of the material. Hence, we also calculated the complex dielectric function, optical absorption spectrum, refractive index, and extinction coefficient. The optical absorption spectrum was interpreted based on the determined electronic structure. The direct optical absorption edge of the material was characterized by the electronic transitions from O 2p states to Te 5s states and from Ni 3d states to O 2p states. This description did not agree with previous ones based on DFT + U calculations or those made based on the electronic structure of the Ni3V2O8 compound. Thus, an alternative description of the electronic structure of the R3 Ni3TeO6 compound in its antiferromagnetic state using the DFT + mBJ calculations has been suggested, and consequently a new origin for the optical absorption observed around the optical band gap.

Ambiguity in indexing electron diffraction patterns of R 3 crystals

The R3 space group inherently lacks 2110, m001 and m_{{\bar 1}10} symmetry operations. However, in crystals with R3 symmetry, these transformations produce `pseudoplanes' with the same interplanar spacing and angles as the original crystallographic planes, causing a lack of uniqueness in the electron diffraction (ED) pattern. The difference in atomic arrangements of pseudoplanes and original planes is reflected in the intensities of diffraction spots; it is hard to differentiate in standard ED patterns, frequently causing wrong assignment of the zone axes. The implications of this ambiguity in analysis of crystal orientations are discussed in detail and a suitable routine to follow while indexing R3 ED patterns is proposed.

Structures and Electronic and Hydrogen Storage Properties of Magnesium Scandium Hydrides.

MgH2 is well known as a potential hydrogen storage material. However, its high thermodynamic stability, high dissociation temperature, slow absorption, and desorption kinetics severely limit its application. Aiming at these shortcomings, we try to improve the hydrogen storage property of MgH2 by doping with transition metal Sc atoms. The structures and electronic and hydrogen storage properties of Mg-Sc-H systems have been systematically studied by combining the crystal structure analysis by particle swarm optimization and density functional theory method. The results show that the structure of MgScH8 with the R3 space group is the most stable one, which is proved to be a wide-band gap (2.96 eV) semiconductor. The possible decomposition pathways, which are crucial for the applicability of R3-MgScH8 as a hydrogen storage material, are studied, and the pathway of MgScH8 → ScH6 + Mg + H2 is found to be the most favorable one under 107.8 GPa pressure, while above 107.8 GPa, MgScH8 → Mg + Sc + 4H2 becomes the most thermodynamically stable pathway and releases the maximum amount of hydrogen. Based on the root mean square deviation calculation, it is found that R3-MgScH8 begins to melt at 400 K. The result of ab initio molecular dynamics simulations shows that the hydrogen release capacity (4.04 wt %) can be easily achieved at 500 K, thus making MgScH8 a potential hydrogen storage material.

Five Mesoporous Lanthanide Metal-Organic Frameworks: Syntheses, Structures, and Fluorescence Sensing of Fe3+, Cr2O72-, and H2O2 and Electrochemical Sensing of Trinitrophenol.

When a multicarboxylate aromatic ligand, 3,5-di(2',4'-dicarboxylphenyl)benzoic acid (H5L), was employed, five structurally similar lanthanide metal-organic frameworks (Ln-MOFs), {[Pr10L6(OH)3Cl(H2O)6]·4C2H8N}n (1), {[Nd10L6(OH)4 (H2O)9]·4C2H8N}n (2), {[Gd10L6(OH)4(H2O)3]·4C2H8N}n (3), {[Ho10L6(OH)4 (H2O)3]·4C2H8N}n (4) and {[Er10L6(OH)4(H2O)6]·4C2H8N}n (5), were synthesized and characterized. Single-crystal X-ray structural analyses disclosed that all five Ln-MOFs crystallize in the trigonal R3 space group. They have three-dimensional mesoporous structure featuring the coexistence of binuclear and tetranuclear species as inorganic building units. The mesoporous structure of 3 was verified by the gas adsorption experiment of N2. Fluorescence analysis showed that 3 can selectively detect Fe3+, Cr2O72-, and H2O2; furthermore, it can be used for the electrochemical detection of trinitrophenol. With the merit of an excellent highly sensitive detection performance, 3 has unpredictable application prospects in future research fields.

Detection of Sub‐Terahertz Raman Response and Nonlinear Optical Effects for Luminescent Yb(III) Complexes

AbstractThe development of multifunctional oriented polar crystals combining diverse optical, nonlinear optical, and magnetic phenomena are desirable. Two enantiomorphic assemblies [YbIII(TPPO)3(NCE)3] (E = S (“YbS”), Se (“YbSe”); TPPO = triphenylphosphine oxide) are prepared. Both crystallites show ultralow‐frequency (ULF) Raman scattering for molecular materials with a value of 16 cm−1 (0.48 THz), originating from collective vibrations of the TPPO ligand and pseudohalides, which is supported by ab initio calculations. Moreover, YbS and YbSe crystals exhibit high‐intense second harmonic generation (SHG) phenomena along the threefold rotation c‐axis. The polarization‐variation of the pumping laser electric field experiment performed on single crystals gives a unique insight into the tensor elements constituting the R3 space group. Replacement of thiocyanide with selenocyanide in YbSe compound increases the second harmonic signal attributed to increased polarization. Besides, they also exhibit 4f‐metal centered high‐performance near‐infrared luminescence thermometric properties and weak single‐molecule magnet behaviors. They can also serve as a platform to study the magnetic and linear/nonlinear optical cross effects.

Deconvoluting the Magnetic Structure of the Commensurately Modulated Quinary Zintl Phase Eu11-xSrxZn4Sn2As12.

The structure, magnetic properties, and 151Eu and 119Sn Mössbauer spectra of the solid-solution Eu11-xSrxZn4Sn2As12 are presented. A new commensurately modulated structure is described for Eu11Zn4Sn2As12 (R3m space group, average structure) that closely resembles the original structural description in the monoclinic C2/c space group with layers of Eu, puckered hexagonal Zn2As3 sheets, and Zn2As6 ethane-like isolated pillars. The solid-solution Eu11-xSrxZn4Sn2As12 (0 < x < 10) is found to crystallize in the commensurately modulated R3 space group, related to the parent phase but lacking the mirror symmetry. Eu11Zn4Sn2As12 orders with a saturation plateau at 1 T for 7 of the 11 Eu2+ cations ferromagnetically coupled (5 K) and shows colossal magnetoresistance at 15 K. The magnetic properties of Eu11Zn4Sn2As12 are investigated at higher fields, and the ferromagnetic saturation of all 11 Eu2+ cations occurs at ∼8 T. The temperature-dependent magnetic properties of the solid solution were investigated, and a nontrivial structure-magnetization correlation is revealed. The temperature-dependent 151Eu and 119Sn Mössbauer spectra confirm that the europium atoms in the structure are all Eu2+ and that the tin is consistent with an oxidation state of less than four in the intermetallic region. The spectral areas of both Eu(II) and Sn increase at the magnetic transition, indicating a magnetoelastic effect upon magnetic ordering.

Few-layer In4/3P2Se6 nanoflakes for high detectivity photodetectors.

Metal phosphorus trichalcogenides (MPX3) have attracted extensive attention as promising two-dimensional (2D) layered materials in future electronic and optoelectronic devices. Here, for the first time, few-layer In4/3P2Se6 nanoflakes have been successfully exfoliated from home-made high-quality single crystals. The In4/3P2Se6 crystal belongs to the R3 space group, and possesses a weak van der Waals force between the adjacent layers and a direct bandgap of 1.99 eV. Furthermore, the In4/3P2Se6-based photodetectors show high performances in the visible light region, such as a high responsivity (R) of 4.93 A·W-1, a high external quantum efficiency (EQE) of 1509% and a fast response time, as low as 2.1 ms. In particular, the high detectivity (D) of the devices can reach up to 4.3 × 1013 Jones (light ON/OFF ratio ≈104) under illumination from a 405 nm light at a bias voltage of 1 V, which is favoured by the ultralow dark current (∼100 fA). These excellent performances pave the way for the implementation of In4/3P2Se6 nanoflakes as promising candidates for future optoelectronic detection applications.

A one-dimensional chiral gadolinium complex based on a tartaric acid derivative: crystal structure, thermal behavior and magnetic properties

A new chiral one-dimensional gadolinium coordination polymer [Gd(HDTTA)3(CH3OH)3]n (1) (D-H2DTTA = (+)-Di-p-toluoyl-D-tartaric acid) was synthesized at room temperature, and fully structurally characterized by Infrared (IR), elemental analysis (EA), single-crystal and powder X-ray diffraction (PXRD). The structure analysis shows that complex 1 belongs to the trigonal system with R3 space group and displays an infinite chain structure along the c axis. In 1, each Gd3+ cation is in the tri-capped trigonal prism geometry, and neighboring Gd3+ cations are connected by three partly deprotonated HDTTA− ligands with the Gd···Gd distance of 7.686(1) Å. The circular dichroism (CD) spectrum demonstrates the chirality of the complex. Magnetic studies reveal that complex 1 displays weak antiferromagnetic interactions between Gd3+ cations and it exhibits a small magnetic entropy change (−ΔS m = 7.26 J kg−1 K−1 with ΔH = 7 T and T = 2.5 K) because of long Gd···Gd distance and relatively low magnetic density.

Structural, optical and morphological features of combustion derived Ba3Y4O9: Dy3+ nanocrystalline phosphor with white light emission

A simple and highly efficient route of solution combustion process was utilized for preparing a series of white light emanating Ba3Y4(1-x)O9: 4xDy3+ (x = 0, 1.0, 3.0, 5.0, 10, 15 mol%) nanocrystalline phosphors. The resulted product was claimed to belonging to R3 space group (SG) with trigonal crystal system related to hexagonal crystal family utilizing powder X-ray diffraction (PXRD) technique and Rietveld refinement. The photoluminescence emission spectra comprised of two intense bands; one was yellow band (Y) in consequence of 4F9/2 → 6H13/2 transition positioned at 578 nm and another one was blue band owing to 4F9/2 → 6H15/2 transition sited at 489 nm. Ba3Y3.88Dy0.12O9 composition was considered as optimal composition for white light emission amongst the prepared nanophosphors owing to its maximal intense emission. The morphological aspects and elemental composition of the optimized sample were analyzed with the help of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDAX) studies. CIE (International Commission on Illumination) chromaticity coordinates confirmed the white light emission by all the synthesized nanophosphors that validate their potential applications in white light emitting diodes (WLEDs). Correlated color temperature (CCT) analysis substantiates their applications as cool white light source.

On the Complete 2-Dimensional λ-Translators with a Second Fundamental form of Constant Length

In this article we study the two-dimensional complete λ-translators immersed in the Euclidean space ℝ3 and Minkovski space ℝ13 . We obtain two classification theorems: one for two-dimensional complete λ-translators x: M2 → ℝ3 and one for two-dimensional complete space-like λ-translators x: M2 → ℝ13 , with a second fundamental form of constant length.

Characterizing Novel Honeycomb Infill Pattern for Additive Manufacturing

Abstract Prismatic closed cells, i.e., honeycomb structures, are often used as infill in additive manufacturing (AM) for providing physical stability to the skin and mechanical integrity to the object. These cells are periodic in nature and uniform in density. In this research, a new fabrication pattern for honeycomb infill is proposed for material deposition-based additive manufacturing applications. The proposed pattern uniformly distributes the material within the cell and can accommodate a controllable variational honeycomb infill while maintaining continuity with relative ease. First, the honeycomb unit cell geometry is defined for uniform and non-uniform voxel sizes. A continuous toolpath scheme is then designed to achieve the honeycomb structure with uniform wall thickness. Unlike traditional honeycomb cells, the aspect ratio of the proposed cell type is not restricted, which helps to introduce variational honeycomb architecture in the infill. Additionally, the proposed cell type is four-time smaller than the traditional cell, which increases the unit cell packing density for the same R3 space. The proposed infill structures are fabricated with both uniform and variational patterns, which are then compared with the traditional honeycomb pattern with compression testing. In comparison to the traditional samples, the proposed uniform and variational infill patterns have achieved higher elastic modulus, collapse strength, and absorbed more specific energy along the X-direction. However, the values measured for both proposed patterns are lower along the Y-direction. Similar results are achieved for two different materials (PLA and TPU), which indicates the consistency of our findings.

Two New Ferroborates with Three‐Dimensional Framework and Wide Transmittance Window

Two ferroborates Li5MSrFeB12O24 (M = Mg, Zn) crystallized in trigonal R3 space group, were obtained by high temperature solid state reaction. Centimeter‐level Li5MgSrFeB12O24 single crystals were grown from high temperature solution using Li2B4O7 as a self‐flux. In their structures, [FeO6] octahedra connect with [B2O6] chains by corner‐sharing O atoms forming the three‐dimensional [FeB12O24] framework. The family of ferroborates(III) was summarized and the structural comparison with Ba2MgB6O12 based on cation cosubstitution was also discussed to better understand the crystal structures of Li5MSrFeB12O24 (M = Mg, Zn). The transmittance spectrum of a Li5MgSrFeB12O24 crystal was measured to detect its transmittance window. In addition, thermal behaviors, other optical and magnetic characteristics of Li5MSrFeB12O24 (M = Mg, Zn) were discussed as well.

Kutnohorite CaMn(CO3)2 crystal growth at high pressure-temperature

High quality kutnohorite CaMn(CO3)2 single crystals up to 100 μm in size were successfully achieved under high pressure-temperature (P-T) conditions. Electron microprobe analyses revealed the average wt% of CaO was 25.98% and that of MnO was 32.88%, correspondingly well to the ideal formula of Ca1.0Mn1.0(CO3)2. Accurate crystalline structural data were determined from single-crystal X-ray diffraction (XRD), with the R3 space group and R3c space group used to refine the crystal structure of CaMn(CO3)2. The Ca-O and Mn-O bond lengths were slightly different when using the R3 space group, which were clearly distinguished from those in the dolomite structure. Therefore, R3c is the most probable space group for the CaMn(CO3)2 crystal structure. Thermogravimetric (TG) analysis and differential scanning calorimetry (DSC) showed that CaMn(CO3)2 decomposed from 620–750 °C, but only one endothermic peak was observed during the decomposition process. It indicated that the octahedral units in CaMn(CO3)2 have the same thermal stability due to the complete miscibility of Ca and Mn. The results of single crystal XRD and thermal analysis provided direct evidence that CaMn(CO3)2 has a calcitetype structure, not dolomite-type layered structure, which was in good agreement with the rigid model of rhombohedral carbonates.

A Chiral and Polar Single-Molecule Magnet: Synthesis, Structure, and Tracking of Its Formation Using Mass Spectrometry.

The solvothermal reaction of cobalt(II) sulfate with S, S-1,2- bis(1-methyl-1 H-benzo[ d]imidazol-2-yl)ethane-1,2-diol, (H2L), neutralized with triethylamine (Et3N) in a mixture of methanol and water (2:1), resulted in triangular red crystals of [CoII7(L)3(SO4)3(OH)2(H2O)9]·4H2O·3CH3OH (Co7). It is formed of chiral and polar clusters crystallizing in the R3 space group. Co7 consists of apex-shared asymmetric dicubane units where all of the metals adopt an octahedral coordination and the three ligands wrap diagonally around the unit. One end of the cluster is bonded by six water molecules and the other end by three monodentate sulfates. The head-to-tail packing through extended H-bonds leads to polar chains. The ligand has lost two protons, adopts a cis-conformation, and is coordinated to five metals around the waist of the dicubane. Electrospray ionization mass spectrometry (ESI-MS) of solutions of the reaction as a function of time reveals the possible step-by-step assembly process of the cluster: the initial product [CoII(HL)(SO4)]2- combines with CoSO4, forming [CoII2(HL)(SO4)2]2-, and then, upon addition of Et3N, dimerizes through a [OH]- bridge to [CoII4(HL)2(OH)(CH3OH)2(SO4)3]- followed by capture of one Co2+ and one CoSO4 to form [CoII6(L)2(OH)(CH3O)(SO4)4]2- before eventually binding to CoL to form [CoII7(L)3(OH)2(SO4)4]2-. These results allow us to propose a possible process for the formation of Co7, which is a good example for chiral multidentate chelating ligand-controlled assembly of clusters. Magnetization measurements as a function of the temperature, field, and ac-frequency reveal ferromagnetic coupled moments and single-molecule magnetism (SMM).

Klein–Gordon Oscillator in a Topologically Nontrivial Space-Time

In this study, we analyze solutions of the wave equation for scalar particles in a space-time with nontrivial topology. Solutions for the Klein–Gordon oscillator are found considering two configurations of this space-time. In the first one, the S1×R3 space is assumed where the metric is written in the usual inertial frame of reference. In the second case, we consider a rotating reference frame adapted to the circle S1. We obtained compact expressions for the energy spectrum and for the particles wave functions in both configurations. Additionally, we show that the energy spectrum of the solution associated with the rotating system has an additional term that breaks the symmetry around E=0.