Intense and recoverable piezoluminescence in Pr3+-activated CaTiO3 with centrosymmetric structure

2021 ◽  
Vol 118 (5) ◽  
pp. 053901
Author(s):  
Liu Yang ◽  
Lei Li ◽  
Long-Xiang Cheng ◽  
Ting-Ting Jia ◽  
Fang Hu ◽  
...  
Keyword(s):  
Centrosymmetric Structure

scholarly journals Interplay between Oxo and Fluoro in Vanadium Oxyfluorides for Centrosymmetric and Non-Centrosymmetric Structure Formation

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 603
Author(s):  
Prashanth Sandineni ◽  
Hooman Yaghoobnejad Asl ◽  
Weiguo Zhang ◽  
P. Shiv Halasyamani ◽  
Kartik Ghosh ◽  
...  
Keyword(s):  
Second Harmonic ◽  
Metastable Phase ◽  
Compound I ◽  
Hydrothermal Route ◽  
Prolonged Heating ◽  
Space Group ◽  
Lithium Vanadium Oxide ◽  
Compound Ii ◽  
Unambiguous Assignment ◽  
Centrosymmetric Structure

Herein, we report the syntheses of two lithium-vanadium oxide-fluoride compounds crystallized from the same reaction mixture through a time variation experiment. A low temperature hydrothermal route employing a viscous paste of V2O5, oxalic acid, LiF, and HF allowed the crystallization of one metastable phase initially, Li2VO0.55(H2O)0.45F5⋅2H2O (I), which on prolonged heating transforms to a chemically similar yet structurally different phase, Li3VOF5 (II). Compound I crystallizes in centrosymmetric space group, I2/a with a = 6.052(3), b = 7.928(4), c = 12.461(6) Å, and β = 103.99(2)°, while compound II crystallizes in a non-centrosymmetric (NCS) space group, Pna21 with a = 5.1173(2), b = 8.612(3), c = 9.346(3) Å. Synthesis of NCS crystals are highly sought after in solid-state chemistry for their second-harmonic-generation (SHG) response and compound II exhibits SHG activity albeit non-phase-matchable. In this article, we also describe their magnetic properties which helped in unambiguous assignment of mixed valency of V (+4/+5) for Li2VO0.55(H2O)0.45F5⋅2H2O (I) and +4 valency of V for Li3VOF5 (II).

Magnetic Ground State and Electronic Structure Calculations of PbMnO3 Using DFT

2014 ◽  
Vol 895 ◽  
pp. 420-423 ◽  
Author(s):  
Sathya Sheela Subramanian ◽  
Baskaran Natesan
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Fermi Level ◽  
Ground State ◽  
Density Functional ◽  
Electronic Structure Calculations ◽  
Magnetic Ground State ◽  
Electronic Band ◽  
Structure Calculations ◽  
Centrosymmetric Structure

Structural optimization, magnetic ground state and electronic structure calculations of tetragonal PbMnO3have been carried out using local density approximation (LDA) implementations of density functional theory (DFT). Structural optimizations were done on tetragonal P4mm (non-centrosymmetric) and P4/mmm (centrosymmetric) structures using experimental lattice parameters and our results indicate that P4mm is more stable than P4/mmm. In order to determine the stable magnetic ground state of PbMnO3, total energies for different magnetic configurations such as nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) were computed for both P4mm and P4/mmm structures. The total energy results reveal that the FM non-centrosymmetric structure is found to be the most stable magnetic ground state. The electronic band structure, density of states (DOS) and the electron localization function (ELF) were calculated for the stable FM structure. ELF revealed the distorted non-centrosymmetric structure. The band structure and DOS for the majority spins of FM PbMnO3showed no band gap at the Fermi level. However, a gap opens up at the Fermi level in minority spin channel suggesting that it could be a half-metal and a potential spintronic candidate.

Electrical Properties of Fresnoite Ba2TiSi2O8 Using Impedance Spectroscopy

2013 ◽  
Vol 795 ◽  
pp. 640-643 ◽  
Author(s):  
Rozana A.M. Osman ◽  
Mohd Sobri Idris
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Sintering Temperature ◽  
Second Harmonic ◽  
Conventional Solid State Reaction ◽  
Reaction Phase ◽  
Tetragonal Unit Cell ◽  
Phase Pure ◽  
Very High ◽  
Centrosymmetric Structure

Fresnoite with composition Ba2TiSi2O8 (B2TS2) was first found in 1965, adopting a non-centrosymmetric structure. It also reported to crystallize in a tetragonal unit cell with a=8.52Å and c=5.210Å leading to some possible application as hydrophone, transducer and second harmonic generation and low temperature co-fired ceramics (LTCC). B2TS2 were synthesized by conventional solid state reaction. Phase pure B2TS2 was obtained after heating the pellets at a final sintering temperature of 1230 °C in air at 92 h. Study found that Fresnoite B2TS2 is a type of materials which are not ferroelectric and instead show perfect dielectric insulator behaviour with resistance >106Ωcm at temperatures below 750°C and also shows nonideal debye respone. The activation energy for conduction of B2TS2 samples is very high, indicating that these materials are highly insulating.

Ultra-long-delay sustainable and short-term-friction stable mechanoluminescence in Mn2+-activated NaCa2GeO4F with centrosymmetric structure

2021 ◽  
Vol 406 ◽  
pp. 126798
Author(s):  
Jun-Cheng Zhang ◽  
Xu-Yan Xue ◽  
Yi-Fei Zhu ◽  
Shanshan Wang ◽  
Hong-Wei He ◽  
...  
Keyword(s):  
Short Term ◽  
Centrosymmetric Structure

Structural, electronic and spectroscopic features of the dihydride Pd4(dppm)4(H)22+ cluster catalyst

2001 ◽  
Vol 79 (5-6) ◽  
pp. 552-559 ◽  
Author(s):  
Daniel Meilleur ◽  
Pierre D Harvey
Keyword(s):  
Low Frequency ◽  
Inert Atmosphere ◽  
Electronic Transitions ◽  
Absorption Bands ◽  
Palladium Hydride ◽  
H Nmr ◽  
Significant Difference ◽  
Simple Selection ◽  
Centrosymmetric Structure ◽  
Ft Raman

1H NMR, vibrational, and UV–vis spectroscopic measurements for Pd2(dppm)2Cl2 (dppm = Ph2PCH2PPh2), [Pd4(dppm)4(X)2](BF4)2 (X = Cl, H), and [Pd4(dmpm)4(H)2](Br)2 (dmpm = Me2PCH2PMe2) were performed to address the structure of the recently identified title cluster. Its dmpm analogue was prepared from the reaction between Pd2(dmpm)2Br2 and NaBH4 in methanol under inert atmosphere, and exhibits the expected nonet (rel. int. 1:8:28:56:70:56:28:8:1) at –5.21 ppm (in (CD3)2CO), contrasting with that of Pd4(dppm)4(H)22+ (δ + 5.15 ppm, (CD3)2CO). This significant difference is explained by the presence of the PdH residues in the deshielding region of the dppm-phenyl groups. The vibrational spectra in the low-frequency region are consistent with a centrosymmetric structure, and a scattering at 144 cm–1 in the FT-Raman spectra is observed; a peak that is assigned to ν(Pd2) on the basis of a comparison with the well established M2-bonded Pd2(dppm)2Cl2 data ((Pd2) = 149 cm–1). On the basis of the qualitative temperature behavior of the band maxima and width, the two lowest energy absorption bands in the UV–vis spectra are assigned to d σ [Formula: see text] d σ * type transition. EHMO computations predict four well-isolated frontier MO levels, defined as d σ *(Pd2)/d σ *(PdH) (LUMO + 1), d σ *(Pd2) (LUMO), d σ *(Pd2)/d σ *(PdH) (HOMO), and d σ (Pd2) (HOMO –1), and simple selection rules (u « g) indicate that only two low-energy electronic transitions are orbitally allowed, consistent with the UV–vis findings. Computer modelings show the presence of large cavities above and under the Pd4 plane, described by inner-cavity nonbonded H···H distances of ~5–8 Å.Key words: cluster, palladium, hydride, structure, spectroscopy.

1,10-Phenanthrolinium hydrogensquarate monohydrate—A non-centrosymmetric structure from two non-chiral agents

2009 ◽  
Vol 73 (5) ◽  
pp. 929-935 ◽  
Author(s):  
Ts. Kolev ◽  
B.B. Koleva ◽  
R. Nikolova ◽  
R.W. Seidel ◽  
H. Mayer-Figge ◽  
...  
Keyword(s):  
Centrosymmetric Structure

Structure determination without Fourier inversion. Part II: The use of intensity ratios and inequalities

2006 ◽  
Vol 221 (10) ◽  
Author(s):  
Armin Kirfel ◽  
Karl F. Fischer ◽  
Helmuth W. Zimmermann
Keyword(s):  
Structure Determination ◽  
Fourier Inversion ◽  
One Dimensional ◽  
Intensity Ratios ◽  
Centrosymmetric Structure

AbstractUsing for a one-dimensional centrosymmetric structure of

scholarly journals 2-Bromo-1-chlorophenyl-3-(4-methoxyphenyl)prop-2-en-1-one

2006 ◽  
Vol 62 (4) ◽  
pp. o1578-o1579 ◽  
Author(s):  
William T. A. Harrison ◽  
H. S. Yathirajan ◽  
B. K. Sarojini ◽  
B. Narayana ◽  
K. K. Vijaya Raj
Keyword(s):  
Benzene Ring ◽  
Title Compound ◽  
Molecular Conformation ◽  
Crystal Packing ◽  
Geometrical Parameters ◽  
Ring Systems ◽  
Bond Lengths ◽  
Compound C ◽  
Centrosymmetric Structure

The geometrical parameters for the title compound, C16H12BrClO2, are normal. The observed bond lengths and angles imply that there is little electronic conjugation between the two benzene ring systems. An intramolecular C—H...Br interaction may help to establish the molecular conformation. The crystal packing results in a centrosymmetric structure.

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