Tetragonal Lattice Research Articles

Highly Efficient Separation of C8 Aromatic Isomers by Rationally Designed Nonaromatic Metal-Organic Frameworks.

The separation of C8 aromatics (xylenes and ethylbenzene) remains one of the most challenging industrial separations due to their similar structures and properties. Suitable adsorbents that can distinguish the small differences among isomers are urgently demanded. Herein, we demonstrate a strategy to realize the precise discrimination of C8 aromatics by constructing a nonaromatic confined pore environment with mixed polycycloalkane-type ligands. The nonaromatic low-polar pore environment avoids strong convergent interactions between the framework and the common phenyl rings while creating possibilities to amplify the difference between host-guest/guest-guest interactions regarding the different methyl (ethyl) group positions of isomers. The resultant metal-organic framework, ZUL-C3, with either tetragonal or monoclinic lattice, exhibits outstanding separation performance for C8 aromatics, not only realizing the simultaneous separation of four isomers from each other but also setting a benchmark for the dynamic separation performance of OX/PX and OX/MX.

On mechanical twinning in tetragonal lattice

ABSTRACT The theory of mechanical twinning is revisited for the case of face-centred tetragonal lattices. The motivation is an imprecision in the determination of twinning shear vector magnitude, which occurs repeatedly in the literature. The magnitude of this vector describing the mutual shear of two adjacent crystallographic planes in the process of twin formation is a function of the tetragonality of the lattice c/a. Therefore, we introduce the c/a-dependent factor f which has to be applied to the magnitude of shearing vector instead of the commonly use factor 1/6, which is correct only for perfect cubic lattices. The theory is verified by ab initio calculations of the generalised planar fault energy curves for three tetragonal materials: the nonmodulated martensite phase of Ni2FeGa magnetic shape memory alloy, γ-TiAl intermetallic and pure In. Moreover, the calculations show that the additional modification of shear vector is caused by structural optimisation due to short-range interactions in the vicinity of twin interface, especially for lattices with large deviation of c/a from 1. Such modification cannot be simply predicted from the lattice geometry.

Preparation and photoluminescence performance of BaMoO4:Sm3+ orange–red phosphor

In the present paper, orange–red BaMoO4:Sm3+ phosphor was synthesized by high-temperature solid-phase method. The morphology, elemental composition, crystal structure, photoluminescence performance, and charge compensation mechanism of BaMoO4:Sm3+ were investigated. Results indicated that the BaMoO4:Sm3+ phosphor particles were spherical-like in shape with approximate particle size of 2 μm and contained Ba, Mo, O, and Sm elements. The Rietveld-refinement of X-ray diffraction profile of BaMoO4:Sm3+ was consistent with a tetragonal lattice. Under 404 nm excitation of light, BaMoO4:Sm3+ phosphor showed the strongest emission peak at 649 nm and emitted an orange–red light. When the orange–red phosphor was packaged with a 395 nm UV chip and tested, the color coordinates were (0.3109, 0.3626) under a current of 60 mA, the color rendering index Ra = 81.5, and the color temperature was 6385 K. These results indicated that BaMoO4:Sm3+ red phosphor is suitable as a red light component in WLEDs and has potential practical applications.

Compressive properties analysis and optimization design of vat photopolymerization printed lattice structures formed by polyurethane composites

Based on the Body Centered Tetragonal lattice structure of vat photopolymerization printed polyurethane composites, analytical relations between cell parameters and its compressive elastic modulus are deduced. Furthermore, unified numerical expressions are proposed for the unit cell, single-layer cell, and multilayered cell. Different structures are utilized for simulating calculation and the results show that the analytical solution and simulation outcome are consistent with the experimental tests. A modified genetic algorithm is proposed to optimize the lattice structure and its relative density is greatly reduced under certain stiffness conditions. It is promising to accelerate the development and production of integrated lattice products.

Green's function approach to interacting higher-order topological insulators

The Bloch wave functions have been playing a crucial role in the diagnosis of topological phases in non-interacting systems. However, the Bloch waves are no longer applicable in the presence of finite Coulomb interaction and alternative approaches are needed to identify the topological indices. In this paper, we focus on three-dimensional higher-order topological insulators protected by $C_4T$ symmetry and show that the topological index can be computed through eigenstates of inverse Green's function at zero frequency. If there is an additional $S_4$ rotoinversion symmetry, the topological index $P_3$ can be determined by eigenvalues of $S_4$ at high symmetry momenta, similar to the Fu-Kane parity criterion. We verify this method using many-body exact diagonalization in higher-order topological insulators with interaction. We also discuss the realization of this higher-order topological phase in tetragonal lattice structure with $C_4T$-preserving magnetic order. Finally, we discuss the boundary conditions necessary for the hinge states to emerge and show that these hinge states exist even when the boundary is smooth and without a sharp hinge.

Resonant ultrasound spectroscopy for characterization of lattice instability of shape memory alloys

Shape memory alloys (SMAs) are materials able to undergo reversible displacive transitions between different crystal lattices. This ability is reflected by the elastic constants of the individual phases, as certain combinations of these constants exhibit anomalous softening when the crystal approaches the transformation temperature or when the lattice is destabilized by the presence of mobile interfaces. The lecture will summarize the advantages of using resonant ultrasound spectroscopy (RUS), and in particular its contact-less laser-based modification, for detecting and evaluating these elastic anomalies. Three recently studied cases will be discussed: i) single crystals of ferromagnetic shape memory alloys in which the instability-induced softening couples with magnetoelasticity; ii) fine regular laminates in tetragonal martensitic lattices in which the soft combinations of the elastic constants have to be calculated from the effective elastic response of the microstructure; iii) modulated crystals with highly mobile interfaces that act as strongly-nonlinear mechanical oscillators and where the properties of the interfaces can be achieved by analyzing the non-linearity.

Theoretical prediction of doping iron ions effect on the optoelectronic and magnetic cobalt-based perovskite (Co1-xFexScO3)

The ab-initio framework has taken place by means of the Full-potential Linear Augmented Plane-Wave (FP-LAPW) method, using the modified Becke-Johnson exchange potential approximation. This modified method was carried out to study the effects of doping iron ions on the structural, electronic, magnetic, and optical properties of CoScO3 perovskite compound. Doping Fe ions have formed a nonstoichiometric perovskite Co1-xFexScO3 where x = 0, 0.25, 0.50, 0.75, and 1. all doped compounds crystallized in a tetragonal lattice due to the Jahn-Teller effect, while the lattice constant was calculated and found to vary between the value of the two pure compounds. Meanwhile, the stabilities of the studied compounds are shown in the negative values of the formation energy. The magnetic moment was calculated and the whole compounds showed a ferromagnetic behavior. Co1-xFexScO3 perovskite is a potential candidate for spintronic application due to the presence of the half metallic behavior. All optical spectrums including dielectric function, absorption coefficient, reflectivity and refractivity index, and energy loss function show remarkable features for the proposed perovskites.

Spin fluctuations in the 112-type iron-based superconductor Ca0.82La0.18Fe0.96Ni0.04As2

We report time-of-flight inelastic neutron scattering (INS) investigations on the spin fluctuation spectrum in the 112-type iron-based superconductor (FeSC) Ca0.82La0.18Fe0.96Ni0.04As2 (CaLa-112). In comparison to the 122-type FeSCs with a centrosymmetric tetragonal lattice structure (space group ) at room temperature and an in-plane stripe-type antiferromagnetic (AF) order at low temperature, the 112 system has a noncentrosymmetric structure (space group ) with additional zigzag arsenic chains between Ca/La layers and a magnetic ground state with similar wavevector but different orientations of ordered moments in the parent compounds. Our INS study clearly reveals that the in-plane dispersions and the bandwidth of spin excitations in the superconducting CaLa-112 closely resemble to those in 122 systems. While the total fluctuating moments /Fe are larger than 122 system, the dynamic correlation lengths are similar (ξ ≈ 10 Å). These results suggest that superconductivity in iron arsenides may have a common magnetic origin under similar magnetic exchange couplings with a dual nature from local moments and itinerant electrons, despite their different magnetic patterns and lattice symmetries.

Role of electromagnetic gauge-field fluctuations in the selection between chiral and nematic superconductivity

Motivated by the observation of nematic superconductivity in several systems, we revisit the problem of the leading pairing instability of two-component unconventional superconductors on the triangular lattice -- such as $(p_{x},\,p_{y})$-wave and $(d_{x^{2}-y^{2}},\,d_{xy})$-wave. Such a system has two possible superconducting states: the chiral state (e.g. $p+ip$ or $d+id$), which breaks time-reversal symmetry, and the nematic state (e.g. $p+p$ or $d+d$), which breaks the threefold rotational symmetry of the lattice. Weak-coupling calculations generally favor the chiral over the nematic superconducting state, raising the question of what mechanism can stabilize the latter. Here, we show that the electromagnetic field fluctuations can play a crucial role in selecting between these two states. Specifically, we derive and analyze the effective free energy for the two-component superconducting order parameter after integrating out the gauge-field fluctuations, which is formally justified if the spatial order parameter fluctuations can be neglected. A non-analytic cubic term arises, as in the case of a conventional $s$-wave superconductor. However, unlike the latter, the cubic term depends on the relative phase and on the relative amplitudes between the two order parameter components, in such a way that it generally favors the nematic state. This result is a direct consequence of the fact that the stiffness of the superconducting order parameter is not isotropic. Competition with the quartic term, which favors the chiral state, leads to a renormalized phase diagram in which the nematic state displaces the chiral state over a wide region in the parameter space. We analyze the stability of the fluctuation-induced nematic phase, generalize our results to tetragonal lattices, and discuss their applicability to candidate nematic superconductors, including twisted bilayer graphene.

STRUCTURAL STABILITY OF Ti-N AND Zr-N COATINGS AT EMISSION TESTS IN MODE OF PULSES

In this work, stability of titanium and zirconium nitride coatings deposited on steel and molybdenum was studied. The phase composition of nitride coatings was studied by X-ray method before and after emission testing in the nanosecond range of pulses. It was noted that before the testing, the titanium nitride coating was a successive alternation of α-Ti, Ti2N, and TiN layers. After the testing, titanium was transformed into the β-phase (bcc), nitrogen was partially evaporated, and a new phase, presumably Ti3N, with a tetragonal lattice was formed in a significant content. The Zr-N coating, obtained in the form of zirconium mono-nitride, showed structural stability during testing.

Composition‐independent Curie point (Tc) in ferroelectric (1 − x)PbTiO3–xBi(Li1/2Nb1/2)O3 solid solution

AbstractA new ferroelectric solid solution (1 − x)PbTiO3–xBi(Li1/2Nb1/2)O3 has been explored to develop high‐temperature piezoelectric material. An interesting observation has been found regarding its Curie point (TC) and tetragonal lattice strain (c/a − 1). With increasing composition (x), the Curie point (TC) decreases up to x = 0.10 and thereafter remains constant. In concurrence with the TC, the tetragonal lattice strain (c/a − 1) follows a similar trend. Neutron powder diffraction analysis suggests this anomalous behavior is due to the robust off‐centering characteristic of the Bi+3 ion 6S2 lone pair effect at the A‐site compared to ions at B‐site.

Multiband acoustic topological metamaterials with valley-switchable higher-order corner states

Topological insulators have become a hot research area in the field of acoustics in recent years, particularly the recently-appearing higher-order topological insulators (HOTIs) that support low-dimensional corner states. However, most HOTIs reported are implemented in tetragonal lattices, and only support single-frequency operation, which enables the higher-order states to be fixed at specific corners and at specific frequencies, lacking the multiband response and flexibility of switching. Herein, the experimental realization of flexibly valley-switchable topological corner states in multiple frequency bands with acoustic metamaterials in the triangular lattice are reported in a 2D system. The designed topological metamaterials, whose second-order topology is characterized by nontrivial bulk polarization, exhibit diverse topological valley-switchability in different bandgaps, as verified by simulation and experiments. Furthermore, an arbitrary structure containing complex patterns with various crossing angles is designed and experimentally implemented, where selected corners can be switched on or off by valley switching, and the switching modes are distinct in different bandgaps. The reported valley topological metamaterials enrich the fundamental understanding of the interaction between multiband higher-order topology and valley degrees of freedom, which inspire potential applications for multiband communication devices and integrated acoustics and photonics.

The distribution and substitution mechanism of trace elements in cassiterites: Constraints from LA-ICP-MS U[sbnd]Pb dating, elemental mapping and in situ trace element analyses of the Gejiu tin polymetallic deposit, SW China

The tetragonal lattice structure enables cassiterites to incorporate dozens of elements within their crystal lattice (e.g., Fe, Ti, W, Zr, Hf, Ta, Nb, Mn, Sc, V and Sb). Thus, it is anticipated that variations of these elements should record information of potential elemental substitution mechanisms and precipitation environments of cassiterites. With moderate amounts of U and Pb, cassiterites can be dated with U-Pb geochronology. In this study we collected cassiterite grains from six different ore types within the Gejiu tin polymetallic deposit to perform LA-ICP-MS U-Pb dating, multiple element mapping and in-situ trace element analysis. Systematic U-Pb dating of such cassiterites yielded Tera-Wasserburg lower-intercepted ages ranging from 81.91 ± 0.62 to 85.7 ± 1.4 Ma, coinciding, within their respective analytical uncertainties, with zircon U-Pb ages of regional Late-Yanshanian granitoids. Such age coincidence, combined with spatial association, suggests that tin mineralization may be genetically related to the late Cretaceous granitic magmatism. Multi-elemental mapping shows that the distribution of Nb, Ta, and Ti in the cassiterite grains correlate well with the regular oscillatory zoning patterns in Cathodoluminescence (CL) images. The relatively high Fe, Ga, Sb, W and U concentrations control the dark luminescing domains in these cassiterite grains. The systematic variations in chemical compositions suggest that trace elements such as Sc, V, Fe and Ga incorporate in cassiterites via coupled substitutions of Sc3+ + V5+ ↔ 2 (Sn, Ti)4+, Fe3+ + Ga5+ ↔ 2 (Sn, Ti)4+ and Fe3+ + OH−↔ Sn4+ + O2− or Fe3+ + H+↔ Sn4+. The covariation of redox sensitive elements such as Fe, Sb, W and U indicates that only ‘tin-granite’-type cassiterites were formed under an oxidized state whereas cassiterites from other ore types were precipitated in a reducing environment.

3D Graphical Optimization for Molecular Effect Model in High Temperature Superconductors Thallium Class [ TC < 0° , TC > 0° ] without Lattice Tetragonal Compounds

In subsequent study series for 3D High Temperature Superconductors (HTCSs), Inverse Least Squares (ILS) and 3D Numerical/Graphical Optimization is the objective for this Molecular Effect Model (MEM) contribution. HTSCs class selected is Thallium group of [ Tl-Sn-Pb-Ba-Si-Mn-Mg-Cu-O ], constrained/extended to [T<sub>C</sub> ? 0° , T<sub>C</sub> > 0° ]. Tetragonal Lattice and Amorphous compounds of this Type II Thallium HTSCs class are not included in this study. Results obtained for Matlab 3D Graphical Optimization techniques are proven/presented. Numerical calculations include 3D Tikhonov Regularization algorithms with mathematical developments for this Thallium class. Thus, results show two strands, 3D surfaces for Graphical Optimization MEM Thallium HTSCs modelling, and MEM analysis of numerical equations. 3D MEM and Numerical Optimization get low error and residuals. Electronics Physics applications emerge from allteh research.

Cycloidal Magnetic Ordering in Noncentrosymmetric EuIrGe3

Successive magnetic phase transitions at TN = 12.2 K, \(T'_{\text{N}} = 7.0\) K, and \(T_{\text{N}}^{*} = 5.0\) K in EuIrGe3, an intermetallic compound with a body centered tetragonal lattice belonging to a polar space group I4mm, has been investigated by neutron diffraction and resonant X-ray diffraction. It is shown that EuIrGe3 exhibits an incommensurate longitudinal sinusoidal order with \(\boldsymbol{q} \sim (0,0,0.792)\) and mq || c-axis in the high temperature phase (\(T'_{\text{N}} < T < T_{\text{N}}\)), which changes to a cycloidal order with \(\boldsymbol{q} = (\delta ',0,0.8)\) (δ′ ∼ 0.017) and mq || ac-plane in the intermediate phase (\(T_{\text{N}}^{*} < T < T'_{\text{N}}\)). In the low temperature phase (\(T < T_{\text{N}}^{*}\)), the cycloidal plane rotates by 45° to have \(\boldsymbol{q} = (\delta ,\delta ,0.8)\) (δ ∼ 0.012). It is also pointed out that the X-ray scattering amplitude from odd-parity magnetic quadrupole due to the polar environment interfere with that from normal even-parity magnetic dipole in the magnetic ordered phase.

Effects of anisotropy on dynamic void collapse and temperature rise in low-symmetry crystals

An investigation into the role of plastic anisotropy on dynamic void collapse and temperature rise in low-symmetry crystals is presented. To describe the influence of local deformation and thermal history on the dynamic process, in this paper, we use the new anisotropic model for low-symmetry crystals developed in [1]. This constitutive model accounts for the influence of the symmetries of tetragonal lattice on both the elastic and plastic response. Based on the results of the finite-element (FE) simulations of voided PETN crystals subjected to dynamic plain strain loadings, it can be concluded that there are significant effects of the crystal orientation on void collapse and on the location of the temperature peaks, which are potential sites for ignition.

Field-tuned ferroquadrupolar quantum phase transition in the insulator TmVO4

We report results of low-temperature heat-capacity, magnetocaloric-effect, and neutron-diffraction measurements of TmVO4, an insulator that undergoes a continuous ferroquadrupolar phase transition associated with local partially filled 4f orbitals of the thulium (Tm[Formula: see text]) ions. The ferroquadrupolar transition, a realization of Ising nematicity, can be tuned to a quantum critical point by using a magnetic field oriented along the c axis of the tetragonal crystal lattice, which acts as an effective transverse field for the Ising-nematic order. In small magnetic fields, the thermal phase transition can be well described by using a semiclassical mean-field treatment of the transverse-field Ising model. However, in higher magnetic fields, closer to the field-tuned quantum phase transition, subtle deviations from this semiclassical behavior are observed, which are consistent with expectations of quantum fluctuations. Although the phase transition is driven by the local 4f degrees of freedom, the crystal lattice still plays a crucial role, both in terms of mediating the interactions between the local quadrupoles and in determining the critical scaling exponents, even though the phase transition itself can be described via mean field. In particular, bilinear coupling of the nematic order parameter to acoustic phonons changes the spatial and temporal fluctuations of the former in a fundamental way, resulting in different critical behavior of the nematic transverse-field Ising model, as compared to the usual case of the magnetic transverse-field Ising model. Our results establish TmVO4 as a model material and electronic nematicity as a paradigmatic example for quantum criticality in insulators.

Solvent effect on the optoelectronic properties of fluorine doped SnO2 thin films prepared by spray-pyrolysis

This work explores the effects of choice of solvent on the optoelectronic properties of spray-pyrolyzed fluorine (F)-doped tin oxide (SnO2) thin films deposited on glass substrates over an area of 5 × 5 cm2. A 2-methoxyethanol (C3H8O2) and ethylene glycol (C2H6O2) admixture in varying proportions is used as solvent. The volume of C2H6O2 is varied as 0, 25, 50, and 100 ml in the above admixture. The XRD patterns reveal successful formation of tetragonal SnO2 lattice without any structural change. Upon changing the volume of C2H6O2 in C3H8O2, the textured growth changes from (110) direction to (211) direction. The film thickness is found to vary significantly with varying volume of the mixed solvents. Transmittance is found to increase and reach a maximum value of 75% (at 550 nm) for the film deposited with only C2H6O2. The photoluminescence emission data reveals that the overall intensity of violet emission is found to quench upon increasing the volume of C2H6O2. The sheet resistance is found to decrease gradually with increasing volume of C3H8O2 and is found to be the lowest with a value of 6.34 Ω/□ for complete 100 ml of C3H8O2. The surface wettability nature of the thin films obtained from contact angle measurements indicate changeover from hydrophobic to hydrophilic nature (104.4° to 52.2°) with increasing C2H6O2 vol in the admixed solvent. Among all these samples, the film prepared with 100% C2H6O2 solvent shows highest figure of merit value of 3.02×10–3 Ω–1. The optimal film prepared with complete C2H6O2 solvent has surface work function of 4.69 eV and shows highest power conversion efficiency of 2.21% when used in a dye-sensitized solar cell compared to devices fabricated using other admixed solvents. In the solvent admixture, higher volume of C3H8O2 is beneficial for obtaining low sheet resistance, whereas higher volume of C2H6O2 leads to high transmittance, thereby permitting to fix the solvent concentration based on the need for optical transparency and electrical sheet resistance as per custom requirements for a specific optoelectronic application.

2D Graphical Optimization for Molecular Effect Model in High Temperature Superconductors Thallium Class [ TC &lt; 0° , TC &gt; 0° ] with Electronics Physics Multifunctional Transmission Line Design

Following High Temperature Superconductors (HTCSs) study series, Inverse Least Squares (ILS) 2D Numerical/Graphical Optimization is applied on Molecular Effect Model (MEM). Selected HTSCs class is Thallium group of [ Tl- Sn-Pb-Ba-Si-Mn-Mg-Cu-O ], constrained to [T&lt;sub&gt;C&lt;/sub&gt; ? 0° , T&lt;sub&gt;C&lt;/sub&gt; &gt; 0° ]. Tetragonal Lattice and Amorphous compounds of this Type II Thallium HTSCs are not included at this research stage. Solutions with Matlab 2D Graphical Optimization techniques to validate primarily the MEM sinusoid-shape analytical geometry are presented. Programming-methods and imaging processing comparisons with GNU-Octave and Freemat software are also shown. Results comprise 2D Tikhonov Regularization algorithms with mathematical methods for this class. Findings obtain acceptable Numerical and 2D Graphical Optimization outcomes with low error-residuals. Results show two parts, the 2D Graphical Optimization MEM modelling, and MEM comparative imaging processing systems with examples and analysis of several numerical equations and predictions. Applications of MEM for the overview of the Multifunctional Transmission Line for SCs and HTSCs are included. Electronics Physics usages for Superconducting Multifunctional Transmission Lines, Superconductors in general, and HTSCs are presented.

Two-dimensional tetragonal and hexagonal lattices of transition metal carbides MC (M = Ti, Zr, Hf): Observation of two nodal loops and strong light-harvesting ability

Two-dimensional (2D) transition metal carbides (TMCs) have captured immense interest for their fascinating physical and chemical properties. Among them, bare carbide MXenes exhibit a metallic feature, greatly limiting the potential applications in optoelectronic devices. Herein, based on the particle swarm optimization and first-principles calculations, we predicted the existence of two single layer (SL) TMCs, namely, tetragonal β-MC and hexagonal γ-MC (M = Ti, Zr, Hf). The two structures are more stable than previously reported α-MC and possess semimetal and semiconductor properties, respectively. We further reveal that the β-MC monolayers have two nodal loops around the Fermi level. SL γ-TiC, ZrC, and HfC have a bandgap of 1.59, 1.24, and 1.57 eV, respectively, and display strong light-harvesting ability in the visible light range. Our research expands the 2D TMCs family beyond the extensively existing MXenes and greatly enriches the carbon chemistry.