Calculation of Energy Levels of Cerium in Inorganic Scintillator Crystals

1994 ◽  
Vol 348 ◽  
Author(s):  
J. Andriessen ◽  
P. Dorenbos ◽  
C.W.E. van Eijk
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Energy Gap ◽  
Energy Levels ◽  
Fair Agreement ◽  
High Symmetry ◽  
Inorganic Scintillator ◽  
Low Symmetry

ABSTRACTFully relativistic ab initio calculations have been performed on energy levels of cerium in BaF2, LaF3, YAP and YAG. Also nonrelativistic calculations were done on cerium in LSO. The results are in fair agreement with experiment. Both the splitting of the 4f and 5d levels and the 4f–5d energy gap can be explained in the high symmetry crystal BaF2 as well as in the low symmetry crystals LaF3, YAP, YAG and LSO.

ab initio MO Optimization of Molecular Structures of Fluoro- and Chloro-Substituted Dibenzo-p-dioxines and the Effect of Halogen Substitution at the 2,3,7,8-Positions on Metabolic Attack

1997 ◽  
Vol 52 (11) ◽  
pp. 1418-1431 ◽  
Author(s):  
Roland Weber ◽  
Till Kühn ◽  
Hanspaul Hagenmaier ◽  
Günter Häfelinger
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Energy Gap ◽  
Substituent Effects ◽  
Molecular Structures ◽  
X Ray ◽  
Degree Pattern ◽  
Chlorine Substituent ◽  
Homo Lumo ◽  
Good Agreement

Full ab initio optimizations were performed on the molecular structures of 24 fluorinated and chlorinated dibenzodioxines (PFDD/PCDD ) and dibenzofurans (PFDF/PCDF). Reasonable agreement was found by comparing the geometries of four calculated structures with known X-ray data from the literature. For the fluorine substituent, calculated electron densities (Mulliken total charges and π-electron charges) clearly demonstrate the opposite influence of the inductive (I) and mesomeric (M) effect. The changes in π-densities at carbons in ortho-, meta- and para-position are constant for each fluorine substituent (independent of degree, pattern, and position of substitution). It is thus possible to calculate the π-densities of the substituted dioxines by increments starting from dibenzodioxine. π-Charges from quantum mechanical calculations and the increment system show good agreement even for OctaFDD (O8FDD ), where eight substituent effects are acting additively. Compared with fluorine, the chlorine substituent exercises a smaller -I-effect and a clearly weaker +M-effect. The HOMO coefficients of the unsubstituted dibenzodioxine and dibenzofuran, extracted from ab initio calculations, yield a good explanation for the observed regioselective metabolic attack at the 2,3,7,8-positions. The squares of the HOMO-coefficients of the 2,3,7,8-positions in dibenzodioxine (DD ) are about ten times greater than those of the 1,4,6,9-positions. These HOMO coefficients are practically unaffected by halide substitution. But halogen substitution reduces strongly the electron density at the halogen-bound carbon, which, however, is a necessary prerequisite for the electrophilic oxygen transfer during metabolism. One would therefore expect halogen substitution of dibenzodioxine and dibenzofuran (DF) at the 2,3,7,8-position to hinder metabolism, as is indeed found. This provides a plausible explanation for the highly selective tissue retention of 2,3,7,8-substituted PCDDs and PCDFs. Our ab initio calculations of five tetra CDDs (T4CDDs) confirm the postulate of Kobayashi et al. [1 ] who, using semiempirical calculations, found a correlation between the toxicity of a dioxine congener and its absolute molecular hardness. The 2,3,7,8-T4CDD also exhibits the smallest absolute hardness (derived from the HOMO-LUMO energy gap) in our calculations.

scholarly journals Pseudo Jahn−Teller Origin of the Proton Tunneling in Zundel Cation Containing Water Clusters

2021 ◽  
Vol 57 (11) ◽  
pp. 1149
Author(s):  
I. Geru ◽  
N. Gorinchoy ◽  
I. Balan
Keyword(s):  
Ab Initio ◽  
Electronic Structures ◽  
Water Clusters ◽  
Electronic States ◽  
Adiabatic Potential ◽  
Water Molecules ◽  
High Symmetry ◽  
Proton Tunneling ◽  
Jahn Teller ◽  
Low Symmetry

The pseudo Jahn–Teller (PJT) origin of the proton transfer barrier in the Zundel cation at different O–O distances and in an H5O2+(H2O)4 cluster is revealed by means of  ab initio calculations of their electronic structures and the adiabatic potential energy curves. The vibronic constants in this approach were estimated by fitting the ab initio calculated adiabatic potential to its analytical expression. It is shown also that the high-symmetry nuclear configurations ofproton-centered water clusters of the type H+(H2O)n (n = 6, 4, 3) are unstable with respect to the low-symmetry nuclear distortions leading to forming the dihydronium cation H5O2+ and the appropriate number of water molecules: H2n + 1On+ →  (n – 2)H2O + H5O2+. The reason for this instability and the subsequent decay is the PJT coupling between the ground and excited electronic states.

scholarly journals Vibronic Origin of the “SKEWED” Anticline Configuration of the Hydrogen Peroxide Molecule

2008 ◽  
Vol 3 (1) ◽  
pp. 105-111
Author(s):  
N. N. Gorinchoy ◽  
I. Ya. Ogurtsov ◽  
Ion Arsene
Keyword(s):  
Hydrogen Peroxide ◽  
Electronic Structure ◽  
Potential Energy ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Adiabatic Potential ◽  
Potential Energy Curves ◽  
High Symmetry ◽  
Analytical Expression ◽  
Peroxide Molecule

The vibronic origin of instability of the symmetrical forms (D¥ h, C2h and C2v) of the hydrogen peroxide molecule H2O2 was revealed using ab initio calculations of the electronic structure and the adiabatic potential energy curves. The vibronic constants in this approach were estimated by fitting of the ab initio calculated adiabatic potential in the vicinity of the high-symmetry nuclear configurations to its analytical expression. It was shown that the equilibrium “skewed” anticline shape of the C2 symmetry can be realized in two ways: D¥h ® C2v® C2 or D¥h ® C2h® C2 with the decreasing of the adiabatic potential energy at every step.

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.

Cluster Models of Doped Ionic Crystal Scintillators. Quantum Calculations+

1994 ◽  
Vol 348 ◽  
Author(s):  
M. Berrondo ◽  
J.F. Rivas-Silva ◽  
J.B. Czirr
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Ionic Crystal ◽  
Energy Gap ◽  
Alkali Halides ◽  
Alkali Cation ◽  
Quantum Calculations ◽  
Pure Crystal ◽  
Absorption And Emission ◽  
Quantum Electronic

ABSTRACTWe have performed quantum electronic ab initio calculations of clusters of alkali halides, both pure and doped. In order to estimate the pure crystal energy gap and the dopant excitation, we have considered a central cation and four shells of ions surrounding it. We have studied KC1, Nal, NaCl and KI, both pure and with a Tl+ ion replacing thecentral alkali cation. Encouraging results are presented for absorption and emission.

Ab Initio Phonon Dispersion Curves Used to Check Experimentally Determined Elastic Constants of the MAX Phase Ti3SiC2

2011 ◽  
Vol 275 ◽  
pp. 135-138 ◽  
Author(s):  
Oliver Kirstein ◽  
Jian F. Zhang ◽  
Erich H. Kisi ◽  
D.P. Riley
Keyword(s):  
Ab Initio Calculations ◽  
Single Crystal ◽  
Ab Initio ◽  
Elastic Constants ◽  
Phonon Dispersion ◽  
Shear Stiffness ◽  
Max Phase ◽  
High Symmetry ◽  
Max Phases ◽  
Ternary Carbide

The ternary carbide Ti3SiC2 is the archetype of MAX phases. To date, MAX phases have proven difficult to synthesize as sufficiently large single crystals from which single crystal elastic constants might be obtained. Therefore, the elastic properties not only of Ti3SiC2 but other MAX phases are extensively studied by ab initio methods. Recently single crystal elastic constants were experimentally determined for the first time using neutron diffraction. The experiment revealed extreme shear stiffness which is not only quite rare in hexagonal materials but also strongly contradicts the predictions of all published MAX phase elastic constants from ab initio calculations. In the present paper we would like to show that such shear stiffness can possibly be supported by ab initio calculations and the calculated phonon dispersion along high symmetry directions.

Determination of the Electronic Energy Levels of Colloidal Nanocrystals using Field-Effect Transistors and Ab-Initio Calculations

2014 ◽  
Vol 26 (32) ◽  
pp. 5639-5645 ◽  
Author(s):  
Satria Zulkarnaen Bisri ◽  
Elena Degoli ◽  
Nicola Spallanzani ◽  
Gopi Krishnan ◽  
Bart Jan Kooi ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Energy Levels ◽  
Electronic Energy ◽  
Colloidal Nanocrystals ◽  
Electronic Energy Levels
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