The electronic structure and optical properties of a red phosphor, ${\mathrm{Y}}_{2}$${\mathrm{O}}_{3}$:Eu, have been studied using the first-principles molecular-orbital band-structure methods. Using calculated one-electron energy levels, several host material phosphor based on host-impurity interactions explained. However, it has found that luminescence ${\mathrm{Eu}}^{3+}$ require spin-orbit effects to be included in computational

The electronic structure and associated properties of antimony-doped tin (IV) oxide have been studied using both the self-consistent-field scattered-wave molecular-orbital cluster approach augment- ed-spherical-wave supercell band-structure approach. calculated energy eigenvalues wave functions used to interpret several interesting optoelectronic this defect semiconductor. nature origin gap from optical-absorption studies valence-band ultraviolet photoelectron spectroscopy (UPS)...

Producing white light using near-UV LEDs requires the development of new phosphors, as well modification certain existing ones. In this review, we discuss luminescent properties potential phosphors: oxides, silicates, phosphates and nitrides. We evaluate phosphors that employ 4f-5d transitions, line emission, use sensitizers transition metal elements. include information on optical transitions how these can limit selection a composition.

During the past few years there has been a significant progress in adapting properties of non-Cd quantum dots (QDs) for lighting applications. It includes synthesis novel materials, improvement efficiency and thermal stability, most importantly, manufacturability on scale large enough to meet needs industry. In this paper, we review characteristics three mature QD material systems, InP, CuInS2 doped ZnS/ZnSe, from perspective Of these InP-based QDs with core/shell structure are now available...

As the lighting industry transitions from traditional technologies to solid state (SSL), it appears that most preferred way generate white light using SSL technology has been use phosphor-converted emitting diodes (pc-LEDs). There considerable debate in literature whether near-UV LEDs or blue should be used excite phosphors for light. Quite often, phosphor literature, efficiencies of 365 nm 470 are somewhat neglected this debate. In paper, we have provided data on external quantum efficiency...

With use of an unrestricted Hartree-Fock self-consistent-field cluster approach, the potential experienced by a muon in diamond has been investigated. The results strongly indicate that normal muonium is localized tetrahedral interstitial space. By using calculated spin density and averaging it explicitly over vibrational motion quantitative explanation obtained for observed reduction hyperfine field as compared to free muonium.

A new determination of the $^{57}\mathrm{Fe}^{m}$ quadrupole moment has yielded value 0.082 b, which is only half currently accepted value. The procedure combined first-principles calculation field gradients at Fe nucleus in Fe${\mathrm{Cl}}_{2}$ and Fe${\mathrm{Br}}_{2}$ molecules with published splittings for those trapped rare-gas matrices. are strongly influenced by iron $3p$ covalency.

With use of a first-principles unrestricted Hartree-Fock cluster procedure, it is demonstrated that (${\ensuremath{\mu}}^{+}{e}^{\ensuremath{-}}$) center trapped near vacancy has all the features hyperfine tensors for anomalous muonium in diamond and silicon obtained from muon-spin-rotation measurements.

${\mathrm{BaMgAl}}_{10}{\mathrm{O}}_{17}:$ ${\mathrm{Eu}}^{2+}$ (BAM) is a commercial, blue emitting lamp phosphor activated by ${\mathrm{Eu}}^{2+}.$ It usually assumed that the Eu ions substitute for Ba occupying Beevers-Ross site in \ensuremath{\beta}-alumina structure. We have investigated this with varying europium concentrations and different synthesis conditions using ${}^{151}\mathrm{Eu}$ M\"ossbauer spectroscopy. Analysis of line shapes reveals pentamodal (or higher) distribution...

The fundamental issue of ``bands versus bonds'' in metal oxides is addressed through the direct comparison results from scattered-wave cluster-molecular-orbital and augmented-spherical-wave band-structure calculations for zinc oxide copper-impurity systems therein. It shown that there a close correspondence between two types calculations, both regard to pure systems. lead coherent understanding luminescence copper oxide.

Many light emitting diode (LED) phosphors have overlapping emission and absorption bands, such as Ce 3+ -doped garnets Eu 2+ silicates, nitrides, oxynitrides. These bands inevitably lead to self-absorption effects through either non-radiative energy transfer mediated via electron-electron correlation process or actual radiative which involves of a photon due spectral overlap. The first has been often discussed in the literature. second investigated this work semi-quantitative formalism....

Using a full-potential band structure approach, we have investigated the work function of barium oxide coated tungsten cathodes in low pressure discharge lamps. The main objective this is to understand why for such lower than that uncoated tungsten. model studied based on well known supposition source thermionic electrons atoms released from coating due chemical reaction with underlying metallic For unrelaxed seven-layer (100) surface oxide, calculated be 2.22 eV, which BaO, Ba, and W metals...

The increasing availability of $^{19}\mathrm{F}^{*}(I=\frac{5}{2})$ and $^{20}\mathrm{F}(I=2)$ quadrupole interaction data by nuclear radiation techniques has crystallized the need for accurate values $Q$ these nuclei. From self-consistent-field calculations on FCl molecule we have obtained $|Q(^{19}\mathrm{F}^{*})|=0.072\ifmmode\pm\else\textpm\fi{}0.004$ barns $|Q(^{20}\mathrm{F})|=0.043\ifmmode\pm\else\textpm\fi{}0.002$, respectively, which are only two-thirds earlier semiempirical estimates.

The electronic structure of aluminum-adsorbed silicon (111) surfaces has been studied by the self-consistent-field Hartree-Fock cluster method with aim obtaining definitive assignments adsorption site(s). Calculations have made for clusters representing at different high-symmetry sites, namely, substitutional, atop, open, and eclipsed. Besides studies all these sites on ideal surfaces, an study a relaxed substrate eclipsed site. Minimization total energies respect to vertical distance adatom...

This paper reports on the synthesis of nano- and submicron sized (Ba1-xSrx)2SiO4:Eu2+ (0 ≤ x 1) green-yellow emitting phosphors prepared by co-precipitation method. Instead using water, N,N-dimethylformamide is used as a solvent. X-ray diffraction analysis shows single phase products after post-synthesis annealing at temperatures > 900°C for = 0. The particles are nearly spherical with narrow size distribution (100 nm–500 nm) depending conditions. photoluminescence emission spectra consist...

This article reports the structural and luminescence characteristics of Eu 2+ ‐activated solid solutions ( KSrPO 4 ) 1− x ·(( Ba , Sr 2 SiO for 0 ≤ 1. These phosphors were prepared by a sol‐gel/Pechini method. The lattice parameters are linearly dependent on . reliability factor from Rietveld analysis is nearly constant independent indicating ·( forms an ideal solution. emission spectra consist two distinct broad bands, which depend : blue ranging 430 to 470 nm green–yellow 515 570 nm. Both...

A number of possible models for the anomalous muonium (${\mathrm{Mu}}^{\mathrm{*}}$) center in elemental semiconductors diamond, silicon, and germanium are investigated detail, both with respect to their stabilities abilities explain extensive available experimental hyperfine-interaction data, latter being major focus present work. Using unrestricted Hartree-Fock cluster procedure, electronic structures potential-energy curves associated muon positions obtained different models. The results...

Using first-principles band structure methods, the electronic and local geometry of oxygen impurities in GaN have been investigated as a function concentration. The concentrational variation has simulated using various supercells. In order to test validity ``rigid band'' models usually employed describe effect on associated properties wide gap semiconductors, spatial localization donor states with atoms at nitrogen site carefully explored. For all supercells studied this work, energy bands...