Multipole Interactions Research Articles

Structural elucidation by Raman spectroscopy and analysis of luminescence quenching by the Inokuti-Hirayama model in the Pr3+ doped multi-component silicate photonic films

Thin films of multi-component silica glasses doped with Ca2+ and Pr3+ modifiers were fabricated by the spin coating technique. Surface micrographic images extracted by the Field Emission Scanning Electron Microscope revealed a homogeneous texture of the films. Detailed structural analysis by Fourier Transform Raman spectroscopy confirmed the existence of Si-O-Si and polyphosphate groups in the glass matrix. The Burstein-Moss shift was evidenced with doping, by an increase in the band gap of the glass films, evaluated by Tauc’s plots. The films exhibit red and near infra-red emissions (NIR), corresponding to the transitions: 3P0→3F2 and 3P0→3F4 respectively. The decay analysis by the Inokuti-Hirayama (I-H) model validated the contributions of multi-polar interactions particularly that of dipole-quadrupole mechanisms, leading to significant quenching in the highly doped film. The energy transfer efficiency between the sensitizer and activator ions, determined by the formulations of the model was 51.8 %. The decreasing lifetime of the metastable state observed in the glass films could be considered to be prospective for NIR waveguide lasers and red laser sources for optical display screens.

Luminescence and dosimetry approach in terbium(III)-activated tungstate double perovskite.

A series of tungstate double perovskite Ca3 WO6 doped with Tb3+ was prepared by a combustion process using urea as a flux. The crystal structure identification of Ca3 WO6 :Tb3+ phosphors was done using X-ray diffraction patterns, and a monoclinic structure was discovered. The Fourier transform infrared spectrum of Ca3 WO6 :Tb3+ displayed characteristic vibrations of tungstate bonds. Under 278 nm excitation, Ca3 WO6 :Tb3+ exhibited intense downconversion green emission, which corresponded to the 5 D4 -7 FJ (J = 4,5) transitions of Tb3+ . The phosphor exhibited the highest photoluminescence (PL) intensity when it was doped with 1mol% of Tb3+ ; later intensity quenching appeared to be due to the multipolar interaction at higher dopant concentrations. Moreover, high-quality thermoluminescence (TL) was detected when phosphors were irradiated using beta rays. The effects of Tb3+ concentration and beta dose on TL intensity were the two major aspects studied in detail. The TL intensity demonstrated excellent linear response to the applied range of beta dose. The trap parameters of the studied phosphors were computed by the peak shape approach and glow curve deconvolution. The fading effect on TL intensity was studied by recording the TL glow curves after 1 month of beta irradiation. Obtained results from the PL and TL characterizations showed that the phosphors under study have the potential to be used in lighting displays and in thermoluminescence dosimetry.

Fabrication of highly flexible luminescent films, hydro gels and anti-counterfeiting applications of La2MoO6:Sm3+ phosphors

Fabrication of versatile luminescent materials with remarkable quantum yield holds significant importance across various applications. In this context, a series of (1–11 mol %) Sm3+ activated La2MoO6 nanophosphors (LMO:Sm3+ NPs) has been developed. These nanophosphors, denoted as LMO:Sm3+ NPs, serve as a multifunctional platform with applications spanning white LED technology, flexible displays, hydro-gels, and anti-counterfeiting (AC) measures. These phosphors emit a vibrant orange-red light at 601 nm when excited at 402 nm owing to the Sm3+ ions 4G5/2 → 6H7/2 transition, achieving a high quantum yield of 66.2 %. The optimal doping concentration of Sm3+ ions in the LMO host material is identified as 5 mol %, with concentration quenching primarily attributed to electric multi-polar interaction. Remarkably, the newly fabricated LMO:Sm3+ phosphors exhibit a correlated color temperature (CCT) of 2064 K and maintain excellent color stability. Moreover, a transparent AC film is created using the optimized phosphor and Polydimethylsiloxane (PDMS), offering effective AC capabilities through their orange-red emission when exposed to 365 nm UV light. Notably, these phosphors exhibit sustainability, exceptional flexibility, and foldability, expanding their potential applications in the field of AC. These results underscore the potential of LMO:Sm3+ NPs as highly efficient luminescent platforms, catering to a wide range of applications, including white LED's, flexible display devices, hydro-gels, and AC solutions.

Multifunctional Characteristics of BCTH:0.5% Sm3+ Ceramics Prepared via Hydrothermal Method and Powder Injection Molding

Briefly, 0.005-mol Sm3+-doped (Ba0.85Ca0.15)(Ti0.9Hf0.1)O3 ([(Ba0.85Ca0.15)0.995Sm0.005](Ti0.9Hf0.1)O3, BCTH:0.005Sm3+) lead-free ceramics were prepared via hydrothermal method and powder injection molding using paraffin and oleic acid as binders, and the effects of preparation method and sintering conditions on microstructure, dielectric behavior and optical properties were investigated. XRD Rietveld refinement reveals the coexistence of orthogonal, rhombohedral and tetragonal phases, in which the crystal structure and phase fraction are influenced greatly by sintering temperature and holding time. The ceramics present enhanced relaxor behavior and frequency dispersion phenomenon as compared with those prepared by the solid-state sintering method, and the diffusive index γ value is within 1.421–1.673. The transition mechanism and luminescence performance of BCTH:0.005 Sm3+ were analyzed by Blasse formula, photoluminescence spectrum and fluorescence lifetimes, where emission peaks show slight blueshift, fluorescence decay lifetime becomes shorter, electric multipole interaction dominates the energy transfer mechanism, and the down-conversion luminescence is one-photon absorption process. The CIE chromaticity color coordinate (0.4746, 0.5048), correlated color temperature 3134 K and color purity 93.58% are achieved, which reveals that the BCTH:0.005 Sm3+ ceramics express high quality yellow emission rather than orange-red light of the hydrothermal method synthesized nano-powder, and have potential application in optical field.

Exploring luminescent color tunability and efficient energy transfer mechanism of a single-phased hexagonal nanophosphor for white light emitting diodes (WLEDs) application

Nowadays, NUV-triggered phosphor-converted white light-emitting diodes (pc-WLEDs) have gained prominence as substantial alternatives to conventional incandescent and fluorescent lamps as a source of illumination. In this study, we have successfully developed a Tm3+ codoped La2O3:Sm3+ nanophosphor and investigated its potential suitability for application in white light-emitting diodes (WLEDs). X-ray diffraction (XRD) analysis was conducted to examine the phase impurity and structural characteristics of the synthesized nanophosphor. The analysis confirmed the formation of a single-phase La2O3 nanophosphor with a hexagonal crystal structure. The FT-IR spectrum of the synthesized nanophosphor exhibited distinct peaks associated with the vibrational frequencies of La-O bonds. The peaks observed in the fingerprint region of the spectrum, indicate the presence of La-O atoms in the nanophosphor. However, the HR-TEM analysis confirmed that the prepared nanophosphor had a polycrystalline nature and the observed particle sizes lay within the nanoscale range. The incorporation of Tm3+ ions into the host matrix led to a reduction in the optical band gap, leading to enhanced emission intensity. The photoluminescence (PL) study reveals that the Tm3+ ion exhibited blue emission upon excitation at 360 nm, whereas the Sm3+ ion emits reddish-orange light when excited at 379 nm and 408 nm, respectively. However, under 325 nm excitation, the nanophosphor exhibited a white emission color that resulted from the blending of colors emitted by both Tm3+ and Sm3+ ions. This unique finding suggests that this nanophosphor has the potential to generate white light specifically under this particular excitation wavelength. The efficient energy transfer between Tm3+ and Sm3+ ions was attributed to the electric multipolar interaction between the nearest neighbor ions, leading to a quenching phenomenon. Furthermore, the photometric analysis revealed that the correlated color temperatures (CCTs) associated with the emitted white light were found to be higher than 4000 K. Thus, based on these characteristics, it can be inferred that the prepared nanophosphor has the potential to be utilized as a cool white-emitting nanophosphor for single-phased WLEDs application.

The synthesis and luminescence properties of Bi3+/Eu3+ co-doped Gd2O3 phosphors with high thermal stability and tunable emission via energy transfer

In this work, the highly monodisperse (Gd0.99-xBi0.01Eux)2O3 phosphors with spherical morphologies (∼170 nm) are successfully obtained through precursor synthesis via urea-based homogeneous precipitation (UBHP) method, followed by annealing at 1000 °C. The Bi/Eu-doped does not alter the crystal structure, and maintain the cubic structure of the Gd2O3 host. Owing to the Bi3+ occupies two different sites (C2, S6) in Gd2O3 of the cubic phase, the 1S0 → 3P1 transition of Bi3+ has two significant excitation bands (335 nm and 375 nm). By monitoring the excitation at 335 nm and 375 nm, the (Gd0.99-xBi0.01Eux)2O3 phosphors show both Bi3+ (420 nm and 530 nm) and Eu3+ (611 nm) emissions, respectively. The presences of Gd3+ and Bi3+ excitation bands on the PLE spectra by monitoring the Eu3+ emission indicate the Bi3+ → Eu3+ and Gd3+ → Eu3+ energy transfer, respectively, and the energy transfer efficiency is up to 99 %. Meanwhile, the energy transfer mechanism of the (Gd0.99-xBi0.01Eux)2O3 samples is dominated by the dipole-dipole interaction. Under two different excitation wavelengths, the emission intensity varies with the Eu3+ doping content and the quenching concentration is about 3 at%. The calculated value of the critical distance Rc is 12.12 Å, which indicates that the quenching mechanism is mainly caused by the multipole interaction. Meanwhile, the emission color can be tuned though adjusting the Eu3+ content. The temperature-dependent (in the range of 100–500 K) analysis has been obtained, the results indicate the (Gd0.99-xBi0.01Eux)2O3 samples have good thermal stability. The (Gd0.99-xBi0.01Eux)2O3 phosphors developed in this work is expected to be widely used in lighting and optical display applications.

Synthesis and photoluminescence properties of novel orange-emitting Ba2Gd8(SiO4)6O2: Sm3+ phosphors for white LED applications

The solid-state method was utilized to prepare a series of orange-red-emitting Sm3+-doped Ba2Gd8(SiO4)6O2 phosphors. The X-ray powder diffraction patterns indicated that the synthesized phosphors had a pure hexagonal phase. X-ray energy dispersive spectroscopy studies confirmed the elemental composition and distribution of the different elements present in the Ba2Gd8 (SiO4) 6O2: Sm3+ powder. The Sm3+-doped Ba2Gd8 (SiO4) 6O2 phosphors exhibited bright luminescence under 407 nm excitation, with a primary peak at 600 nm. Spectral analysis showed that the Sm3+-doped Ba2Gd8 (SiO4) 6O2 phosphors emitted bright orange-red light. Concentration quenching was detected in Sm3+-doped Ba2Gd8(SiO4)6O2 phosphors with a 0.03 mol% concentration of Sm3+ ions because of the multipolar interaction between the two closest Sm3+ ions. The effective orange-red emission suggests the use of Sm3+-doped Ba2Gd8(SiO4)6O2phosphors for white light-emitting diodes.

Zero sound in a quantum gas of spin-3/2 atoms with multipole exchange interaction

In the context of quantum gases, we obtain a many-body Hamiltonian for spin-3/2 atoms with general multipole (spin, quadrupole, and octupole) exchange interaction by employing the apparatus of irreducible spherical tensor operators. This Hamiltonian implies the finite-range interaction, whereas, for zero-range (contact) potentials parameterized by the s-wave scattering length, the multipole exchange interaction becomes irrelevant. Following the reduced description method for quantum systems, we derive the quantum kinetic equation for spin-3/2 atoms in a magnetic field and apply it to examine the high-frequency oscillations known as zero sound.

Beyond the Maxwell Garnett approximation for interacting plasmonic nanoparticles: An analytical and numerical study

We revisit the issue of building a precise mixing formula for the effective permittivity of interacting assemblies of plasmonic nanoparticles. More precisely, we reconsider the analytical expressions rendered by the Maxwell Garnett and Torquato et al. approximation formulas and compare them to each other and to a numerical approach based on the boundary element method applied to interacting assemblies of metallic (gold or silver) nanoparticles. For efficient numerical simulations of interacting assemblies of relatively large sizes, we set up an algorithm with adaptive surface meshing that depends on the particle’s position within the assembly. Next, we derive expressions for the resonance frequency of the assembly from the analytical formulas, which are valid for gold and silver particle assemblies embedded in matrices with large optical indices. We then compare the analytical results with our numerical findings. We find that the Maxwell Garnett approximation formula underestimates the resonance wavelength and that its validity range in terms of inclusion fraction strongly depends on the nature of the metal and the embedding matrix. In the case of silver particles embedded in high-permittivity matrices, the Maxwell Garnett formula should only be used for low particle concentrations. Torquato’s formula, on the other hand, which accounts for multipolar interactions and the assembly spatial arrangement, renders a better agreement with the numerical simulations.

Achieving perfect white light, color tunability and X-ray scintillation in nanocrystalline La2Hf2O7:Eu3+,Bi3+ by photon energy and doping engineering

Materials which can demonstrate multifunctional lighting efficacy could be boon towards sustainable and developed economy owing to large materials crunch and huge electricity demands. In this work, we have hit three birds with one stone by judicious choice of photon energy and dopant composition engineering in bismuth sensitized Eu3+-doped La2Hf2O7 nanoparticles prepared by a molten salt synthesis method. Bismuth is found to stabilized at both La3+ and Hf4+ sites with Bi@La get excited at high photon energy whereas both Bi@La and Bi@Hf get co-excited at low photon energy to produce perfect amalgam of blue and green Bi3+ emissions upon excitation at 365 nm which couples with Eu3+ red emission and produces white light with (0.31, 0.32) color coordinate. Also, color tunability from violet-blue-purple-pink to orangish red is successfully achieved by efficient Bi3+ → Eu3+ energy transfers via electric multipolar interaction. Density functional theory (DFT) calculations for defect formation energy and density of state (DOS) supported distribution of Bi3+ at both La3+ and Hf4+ sites as well as high feasibility of Bi3+ → Eu3+ energy transfers. Moreover, the La2Hf2O7:0.5%Bi3+,x%Eu3+ NPs demonstrated excellent Eu2+/Eu3+ radioluminescence properties. These characteristics of the La2Hf2O7:0.5%Bi3+,x%Eu3+ NPs described above indicate that these phosphors can be used as potential radioluminescent materials for phosphor converted light emitting diodes and X-ray screen.

Structural, morphological, and optical characteristics of Gd2 Si2 O7 :Dy3+ nanophosphors for WLEDs.

Yellowish-white light-emitting Gd2-x Si2 O7 :xDy3+ (x = 1-5 mol%) nanophosphors were prepared using a solution combustion synthesis method. Fluorescence spectrophotometry and X-ray diffraction measurements were performed to scrutinize the optical performances and phase recognition of the designated nanophosphors. The outcomes specified that the prepared phosphors were crystallized into a triclinic phase with a P-1 space group. As the concentration of Dy3+ ions was increased, the unit-cell volume decrease proportionally due to the replacement of large-sized Gd3+ by small-sized Dy3+ ions. Under ultraviolet excitation at 349 nm, emission spectra consisted of two pronounced emission lines at ~482 nm (blue line), ~578 nm (yellow line), and a relatively weaker emission at ~670 nm (red line) due to 4 F9/2 →6 H15/2 , 4 F9/2 →6 H13/2 , and 4 F9/2 →6 H11/2 intraconfigurational transitions of Dy3+ ions, respectively. The evidence about the site symmetry around Dy3+ ions was examined by considering the ratio of yellow-to-blue emission intensity. The observed critical distance (Rc ) value was ~20.56 Å (≫5 Å), which signified that energy transfer primarily occurred due to multipolar interaction. The obtained coordinates were close to the white region of the Commission Internationale de l'Éclairage chromaticity diagram, which marked a significant milestone in the development of white light-emitting diodes.

An Investigation of Spiral Dislocation Sources Using Discrete Dislocation Dynamics (DDD) Simulations

Discrete Dislocation Dynamics (DDD) simulations are a powerful simulation methodology that can predict a crystalline material’s constitutive behavior based on its loading conditions and micro-constituent population/distribution. In this paper, a 3D DDD model with spiral dislocation sources is developed to study size-dependent plasticity in a pure metal material (taken here as Aluminum). It also shows, for the first time, multipole simulations of spirals and how they interact with one another. In addition, this paper also discusses how the free surface of a crystalline material affects the plasticity generation of the spiral dislocation. The surface effect is implemented using the Distributed Dislocation Method. One of the main results from this work, shown here for the first time, is that spiral dislocations can result in traditional Frank–Read sources (edge or screw character) in a crystal. Another important result from this paper is that with more dislocation sources, the plastic flow inside the material is more continuous, which results in a lowering of the flow stress. Lastly, the multipole interaction of the spiral dislocations resulted in a steady-state fan-shaped action for these dislocation sources.

Open- and Close-Packed, Shape-engineered Polygonal Nanoparticle Metamolecules with Tailorable Fano Resonances.

A top-down lithographic patterning and deposition process is reported for producing nanoparticles (NPs) with well-defined sizes, shapes, and compositions that are often not accessible by wet-chemical synthetic methods. These NPs are ligated and harvested from the substrate surface to prepare colloidal NP dispersions. Using a template-assisted assembly technique, fabricated NPs are driven by capillary forces to assemble into size- and shape-engineered templates and organize into open or close-packed multi-NP structures or NP metamolecules. The sizes and shapes of the NPs and of the templates control the NP number, coordination, interparticle gap size, disorder, and location of defects such as voids in the NP metamolecules. The plasmonic resonances of polygonal-shaped Au NPs are exploited to correlate the structure and optical properties of assembled NP metamolecules. Comparing open- and close-packed architectures highlights that introduction of a center NP to form closed-packed assemblies supports collective interactions, altering magnetic optical modes and multipolar interactions in Fano resonances. Decreasing the distance between NPs strengthens the plasmonic coupling, and the structural symmetries of the NP metamolecules determine the orientation-dependent scattering response. This article is protected by copyright. All rights reserved.

Broadband transparency of Babinet complementary metamaterials

According to the Babinet principle, the diffraction pattern from an opaque body is identical to that from a hole of the same shape and size. Intuitively, placing two complementary structures such as an opaque metal body and its transparent counterpart one by one may result in destructive or constructive interference leading to unexpected electromagnetic response. We propose a Babinet principle-based metamaterial made of two complementary metal/hole checkerboards. The unit cell of each layer is either a metal square with 1/4 of 8 neighboring squares, four of which are made of metal, whereas the other four are square holes, or vice versa. Being placed complementary at optimal distance equal to three-unit cell length, the compound bi-layered Babinet structure demonstrates absolute transparency in a very broad frequency range. The observed absolute transparency of the bi-layered Babinet metasurface is the result of the modified multipole interaction of layers with shifted centers of radiation. We demonstrate both theoretically and experimentally absolute transmission of 0 dB for the Babinet metamaterial made of 3 cm sized Cu squares and complementary holes in the broad frequency range from 4.5 to 6.62 GHz in simulations and from 4.6 to 6.4 GHz in the experiment when the distance between two layers is 1.2 cm. Moving layers toward each other leads to blurring of the resonances. The proven concept of simple, reproducible, and scalable design of the Babinet metamaterial paves the way for the fabrication of broadband transparent devices at any frequency, including THz and optical ranges. The main advantage of broadband Babine metamaterials is applications in optical switching, sensing, filtering, and slow light devices.

Monte Carlo simulations and molecular discrete perturbation theory of multipolar oblate Kihara fluids

The vapor-liquid coexistence of oblate Kihara fluids embedding both point dipole or quadrupole moments has been determined within the framework of the Gibbs ensemble Monte Carlo method and predicted by the molecular discrete perturbation theory. For dipolar models, we explored both axial and non-axial orientations of the dipole moment with respect to the molecular axis. The discrepancies between theoretical and simulations results are discussed in terms of both the reliability of the approximations in which the free energy terms in the perturbation expansion for molecular fluids are based and of the aggregation features found in the structural distribution functions of the liquid phases close to the coexistence boundary, more prominent for highly anisotropic fluids. As a last output of the study, we found a non-monotonous behavior of the critical properties for dipolar models that seems to be wedded to that structuring/aggregation effects, mostly induced by the strongly oriented multipolar interactions.

Effect of Ce3+ Content and Annealing Temperature on the Optical and Scintillation Properties of Ce3+‐Doped Y3Al5O12 Nanoscintillator Synthesized by Sol–Gel Route

Herein, details on the effect of Ce3+ concentration and annealing temperature on luminescence and scintillation properties of Y3Al5O12:Ce3+ (YAG:Ce3+) nanoscintillator powders, prepared by sol–gel method, have been investigated. Despite extensive research on YAG:Ce3+ single crystal, the behavior of this material at the nanoscale is still not fully understood. The photoluminescence spectra of nanoscintillator powders have been measured and analyzed. To properly assess the scintillation properties, the nanoscintillator sample powders are developed for use as a radiation detector and underwent preparation procedures, including surface homogenization and efficient coupling with a photomultiplier tube window. It is shown that even with nanoscintillator powders, pulse height spectra, with well‐resolved photo‐peak from the Compton edge, and scintillation decay curves are obtained. It is found that 0.5 mol% Ce3+ sample annealed at 1000 °C presents the nonradiative quenching concentration with calculated critical distance of 20.21 Å based on the resonance transfer by electric multipole–multipole interaction. Additionally, the sample detector with 0.5 mol% Ce3+ annealed at 1150 °C exhibits the highest light yield (LY) with value 18 900 ph MeV−1 and a better energy resolution value 10% full‐width and half‐maximum under 662 keV γ‐ray from 137Cs source.

Gravitational-wave tails of memory

Gravitational-wave tails are linear waves that backscatter on the curvature of space-time generated by the total mass-energy of the source. The non-linear memory effect arises from gravitational waves sourced by the stress-energy distribution of linear waves themselves. These two effects are due to quadratic multipolar interactions (mass-quadrupole and quadrupole-quadrupole) and are well known. Also known are the tails generated by tails themselves (cubic "tails-of-tails") and the tails generated by tails-of-tails or vice-versa (quartic "tails-of-tails-of-tails"). In this work, we focus on the cubic "tails-of-memory" corresponding to the mass-quadrupole-quadrupole interaction, as well as the "spin-quadrupole tails", which are due to the cubic interaction between the mass, the total angular momentum and the quadrupole. The tails-of-memory and the spin-quadrupole tails contribute to the asymptotic waveform at the fourth-post-Newtonian (4PN) order beyond quadrupolar radiation.

Anti-thermal quenching behavior of Sm3+ doped SrMoO4 phosphor for new application in temperature sensing

SrMoO4: Sm3+ orange red-emitting phosphors for novel application in temperature measurement were prepared by solid-phase synthesis method. SrMoO4: Sm3+ phosphor with scheelite structure was assigned to tetragonal system and I41/a space group. Sm3+ ions could occupy Sr2+ lattice sites of SrMoO4. SrMoO4: Sm3+ consisted of irregular microparticle with well-crystallized pomegranate seed-like morphology and Sm3+ ions can be evenly distributed in the SrMoO4 matrix. The band gap value of SrMoO4: 1.0%Sm3+ (∼4.228 eV) is less than that of SrMoO4 (∼4.267 eV), which is due to generation of defective energy levels in band gap. The appropriate quenching concentration of Sm3+ was 1.0%, the critical distance is ∼25.57 Å and θ is 7.1, close to 8, which was attributed to dipole−quadrupole interaction type of electric multipolar interaction. SrMoO4:1.0%Sm3+ had excellent thermal stability of the PL peak at 598 nm and 644 nm and anti-thermal quenching property of the PL peak at 530 nm and 563 nm. The activation energy based on the intensity of the PL peak at 598 nm is 0.318 eV. The new dual-model thermometry strategy base on exponential function and modified Boltzmann population distribution would be proposed. SrMoO4:Sm3+ phosphor had the absolute sensitivities of 0.108 K−1 based on exponential function and the relative sensitivities of 0.601% K−1 based on modified Boltzmann population distribution. The excellent anti-thermal quenching and good thermal stability of SrMoO4: Sm3+ phosphors indicate that it has a potential for applications as pc-WLEDs and optical thermometry.

Single- and dual-band emission CaNb2O6:Mn2+: Synthesis and luminescence properties

Now free rare earth ions doped materials have attracted a lot of attention. In this work, CaNb2O6:Mn2+ with a pure phase is synthesized by solid-state method in the reducing atmosphere. The crystal structure and luminescence properties of host (CaNb2O6) and CaNb2O6:Mn2+ are investigated. Host (CaNb2O6) under excitation ultraviolet (UV) light emits blue light. CaNb2O6:Mn2+ can show tunable emission from blue to white. Under excitation 260 nm, blue emission of CaNb2O6:Mn2+ is observed owing to the 4T1(4G) → 6A1(6S) transition of Mn2+. When the excitation wavelength is 314 nm, CaNb2O6:Mn2+ emits white light due to the 4T1(4G) → 6A1(6S) transition of Mn2+ and the 6A1(6S)4T1(4G) → 6A1(6S)6A1(6S) transition in Mn2+ - Mn2+ dimers. We measure the concentration dependent spectra of CaNb2O6:Mn2+ and make sure the optimal Mn2+ doping concentration (∼0.8 mol%). We infer that the concentration quenching mechanism is the electric multipolar interaction between nearest-neighbor ions. Based on the temperature dependent spectra of CaNb2O6:Mn2+, we came to the conclusion that CaNb2O6:Mn2+ has a good thermal stability. We analyze the concentration and thermal quenching mechanisms and explain the luminous mechanism by the Tanabe-Sugano energy level diagram of Mn2+ ion. This research results provide a framework for creating Mn2+-doped luminescent materials.

How Accurately Can DFT Describe Non-valence Anions?

Weakly bound non-valence anions are molecular systems where the excess electron stabilizes in a very diffuse orbital whose size, shape, and binding energy (∼1-100 meV) are governed by the long-range electrostatic potential of the molecule. Its binding energy comes mainly from charge-dipole or charge-multipole interactions or dispersion forces. While highly correlated methods, like coupled cluster methods, are considered to be the state of the art for describing anionic systems, especially when the electron lies in a very diffuse orbital, we consider here the possibility to use DFT-based calculations. In such molecular anions, the outer electron experiences long-range exchange and correlation interactions. We show that DFT can describe long-range bound states provided that a correct asymptotic exchange and correlation potential is used, namely, that from a range-separated hybrid functional. This opens an alternative to the computationally demanding highly correlated method calculations. It is also suggested that the study of weakly bound anions could help in the construction of new DFT potentials to study systems where nonlocal effects are significant.