scholarly journals Theoretical Investigation of the EPR G-Factor for the Axial Symmetry Ce3+ Center in the BaWO4 Single Crystal

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 804
Author(s):  
Tomasz Bodziony ◽  
Sławomir Maksymilian Kaczmarek
Keyword(s):  
Single Crystal ◽  
Axial Symmetry ◽  
Local Structure ◽  
Local Environment ◽  
Angular Distortion ◽  
Scheelite Structure ◽  
Energy Matrix ◽  
G Factor ◽  
Cerium Ion ◽  
Good Agreement

The parameters g-factor (g||  and  g⊥) together with the local structure of the Ce3+ center in BaWO4 single crystal (scheelite structure crystals) were theoretically investigated using a complete diagonalization procedure of energy matrix (CDM method). The intrinsic parameters were calculated. It is shown that the experimental and the calculated values of the g-factors are in good agreement. The angular distortion has also been calculated. It was found that the polar angles of the impurity–ligand bonding are smaller than in BaWO4 single crystal (Δθ≈1.00 ) . The validity of the results and the changing in the local environment of the impurity–cerium ion is also discussed.

Measurement of growth rates for single crystals and pressed tablets of CuSO4.5 H2O on a rotating disc

1989 ◽  
Vol 54 (11) ◽  
pp. 2951-2961 ◽  
Author(s):  
Miloslav Karel ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Single Crystal ◽  
Single Crystals ◽  
Growth Rates ◽  
Diffusion Coefficients ◽  
Preferred Orientation ◽  
Rotating Disc ◽  
Dissolution Rates ◽  
Rates Of Growth ◽  
Good Agreement

Measured growth and dissolution rates of single crystals and tablets were used to calculate the overall linear rates of growth and dissolution of CuSO4.5 H2O crystals. The growth rate for the tablet is by 20% higher than that calculated for the single crystal. It has been concluded that this difference is due to a preferred orientation of crystal faces on the tablet surface. Calculated diffusion coefficients and thicknesses of the diffusion and hydrodynamic layers in the vicinity of the growing or dissolving crystal are in good agreement with published values.

scholarly journals Full-dimensional quantum stereodynamics of the non-adiabatic quenching of OH(A2Σ+) by H2

2021 ◽  
Author(s):  
Bin Zhao ◽  
Shanyu Han ◽  
Christopher L. Malbon ◽  
Uwe Manthe ◽  
David. R. Yarkony ◽  
...  
Keyword(s):  
Quantum Dynamics ◽  
Previous Analysis ◽  
Branching Ratio ◽  
Energy Matrix ◽  
Elastic Channel ◽  
Electronically Excited ◽  
Oppenheimer Approximation ◽  
Electronic Motion ◽  
Adiabatic Dynamics ◽  
Good Agreement

AbstractThe Born–Oppenheimer approximation, assuming separable nuclear and electronic motion, is widely adopted for characterizing chemical reactions in a single electronic state. However, the breakdown of the Born–Oppenheimer approximation is omnipresent in chemistry, and a detailed understanding of the non-adiabatic dynamics is still incomplete. Here we investigate the non-adiabatic quenching of electronically excited OH(A2Σ+) molecules by H2 molecules using full-dimensional quantum dynamics calculations for zero total nuclear angular momentum using a high-quality diabatic-potential-energy matrix. Good agreement with experimental observations is found for the OH(X2Π) ro-vibrational distribution, and the non-adiabatic dynamics are shown to be controlled by stereodynamics, namely the relative orientation of the two reactants. The uncovering of a major (in)elastic channel, neglected in a previous analysis but confirmed by a recent experiment, resolves a long-standing experiment–theory disagreement concerning the branching ratio of the two electronic quenching channels.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

Study of the 1459-keV level in 19F by the 19F(p,p′γ)19F reaction

1970 ◽  
Vol 48 (7) ◽  
pp. 827-833 ◽  
Author(s):  
S. T. Lam ◽  
A. E. Litherland ◽  
J. J. Simpson
Keyword(s):  
Angular Distribution ◽  
Single Crystal ◽  
Linear Polarization ◽  
Proton Energy ◽  
Branching Ratios ◽  
Mixing Ratio ◽  
Γ Ray ◽  
Good Agreement

The 1459-keV level of 19F was populated by the 19F(p,p′γ)19F reaction at a proton energy of 2.78 MeV. The E2/M1 mixing ratio for the 1459 → 110 keV transition was determined to be [Formula: see text] from a combination of the γ-ray angular distribution and linear polarization and the nuclear lifetime. The γ-ray angular distribution was measured with a coaxial Ge(Li) detector and the γ-ray linear polarization with a planar Ge(Li) detector. The corresponding E2 and M1 transition strengths for a lifetime of 0.084 ± 0.020 ps are found to be [Formula: see text] and 0.10 ± 0.03 W.u. respectively. They are in good agreement with the particle–hole calculations of Benson and Flowers. The branching ratios of the 1459-keV level agree well with those of Poletti et al. The γ-ray transitions from the 1459-keV level provide a good example for demonstrating the usefulness of a single crystal Ge(Li) polarimeter.

Condensation energies for metals on glass and other substrates

1959 ◽  
Vol 252 (1270) ◽  
pp. 418-430 ◽  
Keyword(s):  
Sodium Chloride ◽  
Single Crystal ◽  
Physical Adsorption ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Potassium Bromide ◽  
Binding Energies ◽  
Adhesive Energy ◽  
Good Agreement

Earlier work on condensation phenomena is briefly reviewed, and existing measurements of condensation energies are summarized. Measurements of condensation energies have been made for aluminium, silver and cadmium on glass and for aluminium and silver on single-crystal cleavage surfaces of sodium chloride and potassium bromide. Adhesive energies or binding energies between film and substrate have been calculated in each case. Association energies for nucleation are obtained by difference and shown to be consistent. Results for cadmium show good agreement with earlier work, but results for aluminium do not agree with the earlier results of Rhodin who measured the condensation energies for aluminium on various substrates, obtaining values which suggest chemisorption. These results appear to be too high and a possible explanation is given. It is concluded that the adhesive energy is due to physical adsorption and can be explained in terms of van der Waals forces only.

Achieving high thermal stability of different rare-earth ions in a single matrix host via the manipulation of the local structure by a solid solution

2020 ◽  
Vol 22 (28) ◽  
pp. 16294-16300
Author(s):  
Xiuxia Yang ◽  
Lei Zhao ◽  
Zhichao Liu ◽  
Shuyu Tian ◽  
Hao Zhang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Solid Solution ◽  
Rare Earth ◽  
Local Structure ◽  
Local Environment ◽  
High Thermal Stability ◽  
Rare Earth Ions ◽  
Single Matrix ◽  
Thermal Stability Of

Manipulating the local environment of CAS by substitution of Al3+–Y3+ for Si4+–Ca2+ to achieve more stability in the structure of CYA.

scholarly journals Structural Analysis of the BaWO4 Crystal Doped with Ce and Codoped with Na Ions Based on g-shift Parameters

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 789 ◽  
Author(s):  
Tomasz Bodziony ◽  
Slawomir Maksymilian Kaczmarek
Keyword(s):  
Structural Analysis ◽  
Local Structure ◽  
Perturbation Methods ◽  
Superposition Model ◽  
Shift Method ◽  
Impurity Ions ◽  
Na Ions ◽  
Paramagnetic Ions ◽  
The Relationship ◽  
Good Agreement

The relationship between the g-shift and the local structure of the Ce3+ paramagnetic center with axial symmetry were investigated for four BaWO4 single crystals doped with Ce and codoped with Na. Based on g-shift the displacements of Ce3+ ions are determined. The g-shift method yields displacements of impurity ions in good agreement with the superposition model (SPM) and the perturbation methods (PM) predictions. The structural analysis of the paramagnetic ions and its surrounding in the BaWO4 unit cell was also conducted.

scholarly journals Single-crystal neutron diffraction study of β-Cs3(HSO4)2[H2−x (S x P1−x )O4] (x ≃ 0.5) at 15 K

1999 ◽  
Vol 55 (3) ◽  
pp. 285-296 ◽  
Author(s):  
S. M. Haile ◽  
W. T. Klooster
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Local Structure ◽  
Unit Cell Volume ◽  
Structural Models ◽  
Neutron Diffraction Study ◽  
Unit Cell ◽  
Asymmetric Unit ◽  
X Ray ◽  
Anisotropic Displacement Parameters

The structure of β-Cs3(HSO4)2[H2−x (S x P1−x )O4] has been examined by single-crystal neutron diffraction at 15 K. The compound crystallizes in space group C2/c and contains four formula units in the unit cell, with lattice parameters a = 19.769 (9), b = 7.685 (2), c = 8.858 (3) Å and β = 100.60 (4)°. Refinement of P, S and H site occupancies indicated that the value of x (in the stoichiometry) is 0.500 (6). This, together with the unit-cell volume of 1322.8 (14) Å3, implies a density of 3.463 Mg m−3. The structure contains zigzag rows of XO4 anions, where X = P or S, that alternate, in a checkerboard fashion, with zigzag rows of Cs cations. Moreover, there is one proton site, H(3), with an occupancy of 0.25 and one X-atom site, X(1), that is occupied by 0.5 P and 0.5 S. These features are in general agreement with a previous X-ray structure determination carried out at 298 K. In contrast to the X-ray study, however, it was found that two different structural models adequately fit the diffraction data. In the first model, the proton vacancies and the P atoms were assumed to be randomly distributed over the H(3) and X(1) sites, respectively, and to have no impact on the local structure. In the second model, several atoms were assigned split occupancies over two neighboring sites, to reflect the presence or absence of a proton vacancy, and the presence of P or S on the X(1) site. Refinement assuming the first model, in which anisotropic displacement parameters for 12 of 14 atom sites in the asymmetric unit were employed, yielded residuals w R(F 2) = 0.084 and w R(F) = 0.038. For the second model, in which anisotropic displacement parameters were utilized for only the five atoms that were not split relative to the first model, the residuals were w R(F 2) = 0.081 and w R(F) = 0.036.

scholarly journals X-ray Single-Crystal Structural Analysis of a Magnetically Oriented Monoclinic Microcrystal Suspension of α-Glycine

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 561 ◽  
Author(s):  
Tatsuya Tanaka ◽  
Chiaki Tsuboi ◽  
Kazuaki Aburaya ◽  
Fumiko Kimura ◽  
Masataka Maeyama ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Magnetic Susceptibility ◽  
Single Crystal ◽  
Magnetic Energy ◽  
Powder Sample ◽  
Single Crystal Structure ◽  
X Ray ◽  
Crystal Structural ◽  
The Relationship ◽  
Good Agreement

We previously reported on a method for X-ray single-crystal structure determination from a powder sample via a magnetically oriented microcrystal suspension (MOMS). The method was successfully applied to orthorhombic microcrystals (L-alanine, P212121). In this study, we apply this method to monoclinic microcrystals. Unlike most of the orthorhombic MOMSs, monoclinic MOMSs exhibit two or four orientations with the same magnetic energy (we refer to this as twin orientations), making data processing difficult. In this paper, we perform a MOMS experiment for a powder sample of monoclinic microcrystal (α-glycine, P21/n) to show that our method can also be applied to monoclinic crystals. The single-crystal structure determined in this work is in good agreement with the reported one performed on a real single crystal. Furthermore, the relationship between the crystallographic and magnetic susceptibility axes is determined.

scholarly journals Peculiar Structural Effects in Pure and Doped Functional Single Crystals of Complex Compositions

Molecules ◽  
2020 ◽  
Vol 25 (10) ◽  
pp. 2451
Author(s):  
Galina Kuz’micheva ◽  
Irina Kaurova
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Functional Materials ◽  
Local Environment ◽  
Structural Effects ◽  
Local Structures ◽  
Annealing Conditions ◽  
Activator Ions

Results of a detailed structural characterization of nominally pure and doped single crystals of scheelite, eulytin, and perovskite families obtained by melt methods were considered and analyzed. The influence of growth and post-growth annealing conditions on actual compositions of crystals is shown. The reasons for the coloration of the crystals are explained. A change in crystal symmetry due to crystal–chemical and growth reasons is considered. The use of structural analysis and X-ray absorption spectroscopy is substantiated to reveal the role of activator ions in the formation of statistical and local structures, respectively. A relationship between the distribution of activator ions over crystallographic sites and photoluminescent parameters of materials is established, which allows selecting optimal systems for the application. The combined results of studying single-crystal compounds of other classes (huntite, sillenite, whitlockite, garnet, tetragonal bronzes) allow formulating and summarizing structural effects that appeared in the systems and caused by various factors and, in many cases, due to the local environment of cations. A principal difference in the structural behavior of solid solutions and doped compounds is shown. The methodology developed for single-crystal samples of complex compositions can be recommended for the systematic structural studies of functional materials of different compositions.

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