Ab Initio Site Occupancy and Far-Red Emission of Mn4+in Cubic-Phase La(MgTi)1/2O3for Plant Cultivation

2017 ◽  
Vol 9 (7) ◽  
pp. 6177-6185 ◽  
Author(s):  
Ziwei Zhou ◽  
Jiming Zheng ◽  
Rui Shi ◽  
Niumiao Zhang ◽  
Jiayu Chen ◽  
...  
Keyword(s):  
Ab Initio ◽  
Site Occupancy ◽  
Cubic Phase ◽  
Red Emission ◽  
Plant Cultivation

X-ray powder diffraction study of K2MSiO4, M=Mg, Zn, Co, Cd

1996 ◽  
Vol 11 (1) ◽  
pp. 51-55 ◽  
Author(s):  
W. A. Dollase
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Site Occupancy ◽  
Cubic Phase ◽  
Variable Degree ◽  
Cubic Symmetry ◽  
X Ray ◽  
Constrained Model ◽  
Diffraction Patterns

The title materials are stuffed cristobalites possessing moderate to extreme pseudosymmetry. On the bases of their X-ray powder diffraction patterns, the Mg, Zn, and Cd compounds had been previously reported as cubic and, more recently, the Zn phase as orthorhombic. Newly measured X-ray powder diffraction data demonstrate that all (including the hitherto unknown Co analog) have the Pca21 structure of Na2BeSiO4 at room temperature, but with a widely variable degree of cubic pseudosymmetry. Observed X-ray diffraction data are in good agreement with those calculated by the Rietveld method using a constrained model with Pca21 M2+/Si site occupancy and pseudocentrosymmetric Pcab atom locations. For the most nearly cubic phase, the Cd compound, there is too little deviation in the pattern from cubic symmetry to support atom coordinate refinement even with the constrained model. In these derivatives of the stuffed cristobalite structure family, M2+ and Si atoms form an ordered tetrahedral array which avoids M2+–O–M2+ connections. Potassium atoms fill all of the intervening large cavity sites.

Enhanced deep-red emission from Mn4+/Mg2+ co-doped CaGdAlO4 phosphors for plant cultivation

2019 ◽  
Vol 48 (7) ◽  
pp. 2455-2466 ◽  
Author(s):  
Jianxu Hu ◽  
Tinghong Huang ◽  
Yuanpeng Zhang ◽  
Bin Lu ◽  
Huanqing Ye ◽  
...  
Keyword(s):  
Red Emission ◽  
Plant Cultivation ◽  
Peak Intensity ◽  
Co Doped

Deep-red emission with a peak intensity at 712 nm is observed from the Mn4+/Mg2+ co-doped CaGdAlO4 phosphor for plant cultivation.

scholarly journals Новая тригональная (ромбоэдрическая) фаза SiC: ab initio расчеты, симметрийный анализ и рамановские спектры

2018 ◽  
Vol 60 (10) ◽  
pp. 2022
Author(s):  
Ю.Э. Китаев ◽  
С.А. Кукушкин ◽  
А.В. Осипов ◽  
А.В. Редьков
Keyword(s):  
Ab Initio ◽  
Raman Spectra ◽  
Rhombohedral Phase ◽  
Cubic Phase ◽  
Selection Rules ◽  
Initial Stage ◽  
The Difference ◽  
Si Films ◽  
New Phase ◽  
Sic Film

AbstractA new trigonal (rhombohedral) SiC phase, existence of which was previously theoretically predicted by a symmetry analysis, is studied. It is shown that the phase can be formed during the growth of SiC films by the method of substitution of atoms on the surface of a Si substrate. Ab initio calculations of the crystal structure of a new phase and its Raman spectra are performed by the quantum chemistry method. The difference of the selection rules for the Raman active vibrations for this rhombohedral phase from the selection rules for a cubic phase in the coordinate system aligned with the translation vectors of the rhombohedral phase is established. Series of thin SiC/Si films by annealing time are synthesized by the method of the topochemical substitution of atoms, and their Raman spectra are analyzed. The presence of the spectral line (258 cm^–1), that is close to the line of a new trigonal (rhombohedral) phase calculated by the ab initio method, has been found in the Raman spectra of the samples at the initial stage of the growth of a SiC film, which indirectly confirms its existence.

AB INITIO CALCULATIONS OF INTERMOLECULAR INTERACTION POTENTIALS OF FULLERENE-FRAGMENTS SYSTEMS

2005 ◽  
Vol 04 (01) ◽  
pp. 49-58 ◽  
Author(s):  
YUKIUMI KITA ◽  
KEI WAKO ◽  
ISAMU OKADA ◽  
MASANORI TACHIKAWA
Keyword(s):  
Ab Initio ◽  
Intermolecular Interaction ◽  
Correlation Energy ◽  
Basis Set ◽  
Basis Sets ◽  
Cubic Phase ◽  
Molecular Orbital Calculations ◽  
Interaction Potentials ◽  
Basis Set Superposition Error ◽  
Intermolecular Distances

We have performed the ab initio molecular orbital calculations for combinations of the fullerene-fragments as the models of the nonbonding interaction of C 60 dimer at the preferred configurations in the simple cubic phase. The intermolecular interaction potentials have been calculated using several basis sets with MP2 level of the electron correlation energy and the basis set superposition error correction. The strong dispersion attractions that is dominant in the van der Waals interaction has been found for the combinations of the fullerene-fragments. The equilibrium intermolecular distances obtained are in good agreement with the corresponding experimental value. The repulsive region of the intermolecular interaction calculated by ab initio method is found to be express by an atom–atom interaction potential with an anisotropic exponential type repulsive term, which is less steep than the conventional Lennard–Jones type potential.

scholarly journals Rotation mechanism of methylammonium molecules in organometal halide perovskite in cubic phase: An ab initio molecular dynamics study

2016 ◽  
Vol 145 (22) ◽  
pp. 224503 ◽  
Author(s):  
Kohei Shimamura ◽  
Tomoya Hakamata ◽  
Fuyuki Shimojo ◽  
Rajiv K. Kalia ◽  
Aiichiro Nakano ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Ab Initio Molecular Dynamics ◽  
Cubic Phase ◽  
Organometal Halide Perovskite ◽  
Halide Perovskite

Morphology and optical properties of cubic phase GaN epilayers grown on (001) Si

1998 ◽  
Vol 3 ◽  
Author(s):  
M. Godlewski ◽  
E. M. Goldys ◽  
M. R. Philips ◽  
J. P. Bergman ◽  
B. Monemar ◽  
...  
Keyword(s):  
Optical Properties ◽  
Grain Boundaries ◽  
Strong Influence ◽  
Cubic Phase ◽  
Edge Emission ◽  
Red Emission ◽  
Edge Luminescence ◽  
Spatially Homogeneous

Optical properties of GaN epilayers of a cubic phase are studied. We show a strong influence of the sample morphology on intensity of the edge emission. Whereas edge luminescence is reduced at the grain boundaries, red emission is spatially homogeneous.

Blue absorption and red emission of Bi2+ in solids: strongly spin–orbit coupled 6p levels in low symmetry fields

2014 ◽  
Vol 16 (32) ◽  
pp. 17305-17314 ◽  
Author(s):  
Luis Seijo ◽  
Zoila Barandiarán
Keyword(s):  
Ab Initio ◽  
Radiative Lifetime ◽  
Orbit Coupling ◽  
Oscillator Strengths ◽  
High Symmetry ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Red Emission ◽  
Confinement Potential ◽  
Low Symmetry

Ab initio calculations on a (BiO8)14− cluster under the effects of a high symmetry Oh confinement potential are used to study the energies of the 2P1/2, 2P3/2(1), and 2P3/2(2) spin–orbit coupling levels of the 6s26p configuration of Bi2+ in Oh, D4h, D2h, D4, D2d, D2, S4, C4v, C4, C3v, C2v, C2, Cs, and C1 fields, together with the 2P1/2 → 2P3/2(1) and 2P1/2 → 2P3/2(2) absorption oscillator strengths and the 2P3/2(1) radiative lifetime.

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