Positron annihilation in mordenite zeolite

2021 ◽  
Vol 6 (1) ◽  
pp. 50-55
Author(s):  
Hoa Lang Trinh ◽  
Van Tao Chau ◽  
Hoang Lam Le ◽  
Quoc Dung Tran
Keyword(s):  
Experimental Data ◽  
Positron Annihilation ◽  
Dft Calculation ◽  
Positron Lifetime ◽  
Theoretical Study ◽  
Material Structure ◽  
Accuracy Analysis ◽  
Complicated Structure ◽  
Theoretical Results ◽  
Selection Of

The theoretical study of the positron annihilation in complex material such as zeolite is greatly significant to support and increase the accuracy analysis of the material structure from the experimental data of the positron annihilation. The mordenite zeolite is a big and complicated structure consisting of channels and cavities. The analysis of the mordenite structure is studied by the PALS so depending on the selection of the positron lifetime components of the positron annihilation spectra fitting methods. Therefore, these positron life times in on TO4, Na, Ca, K, Fe, H2O and the rings which form the channels and cavities are sophisticatedly studied by the DFT calculation using Ab-initio. The mordenite and modified mordenite zeolite structures are precisely analyzed, and the physical behaviors of the positron in these are more understood by these theoretical results.

Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Lift Coefficient ◽  
Cavity Surface ◽  
Air Bubbles ◽  
Incoming Flow ◽  
Fluid Density ◽  
Air Content ◽  
Theoretical Results ◽  
Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

scholarly journals Effects of Proximity Potentials on the Cross-Sections of 6,8He + 65Cu Halo Fusion Reactions

2019 ◽  
Vol 64 (5) ◽  
pp. 363
Author(s):  
M. Aygun
Keyword(s):  
Experimental Data ◽  
Cross Sections ◽  
Theoretical Study ◽  
Fusion Reactions ◽  
The Cross ◽  
Theoretical Results

The comprehensive theoretical study is performed to determine the best proximity potentials in reproducing 6,8He + 65Cu fusion reactions. Twenty three different versions of proximity potentials that consist of Prox 66, Prox 76, Prox 77, Prox 79, Prox 81-I, Prox 81-II, Prox 81-III, Prox 84, Prox 88, Mod-Prox-88, Prox 95, Prox 2003-I, Prox 2003-II, Prox 2003-III, Prox 2010, BW 91, AW 95, Bass 73, Bass 77, Bass 80, CW 76, Ngo 80, and D are used. The theoretical results are compared with experimental data on 6,8He + 65Cu fusion reactions. The appropriate proximity potentials are determined.

scholarly journals The DFT calculations of pKa values of the cationic acids of aniline and pyridine derivatives in common solvents

2014 ◽  
Vol 7 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Peter Poliak
Keyword(s):  
Experimental Data ◽  
Chemical Structure ◽  
Reaction Scheme ◽  
Isodesmic Reaction ◽  
Pka Values ◽  
Good Accordance ◽  
Derivatives Of ◽  
Pyridinium Ion ◽  
Theoretical Results ◽  
Selection Of

Abstract The theoretical pKa values of the derivatives of anilinium and pyridinium ions in 7 solvents are presented. For this purpose, the usage of isodesmic reaction scheme using the DFT/B3LYP approach with IEFPCM solvation was evaluated. We have shown that the suitable selection of reference species has the primary influence on the resulting data. For the studied anilinium ion derivatives the nonsubstituted anilinium ion seems to be a satisfactory reference system. The calculated values are in good accordance with the available experimental data with the RMS error of 1.00 and 0.99 pKa units in water and THF, respectively. The highest error in predicted pKa value is less than 2.0 pKa units in all cases. The chemical accuracy of the applied treatment is limited in the case of nitroaniline ions and the maximal therotetical uncertainty for derivatives of the pyridinium ion is within 2.1 pKa units. Our theoretical results enable us to predict the values of pKa for the solvents, where the experimental data are not completely available. Also the influence of the chemical structure on the accuracy of the applied method was discussed.

Positron annihilation in 60Co irradiated alkali halides

1978 ◽  
Vol 56 (12) ◽  
pp. 1527-1530 ◽  
Author(s):  
S. Dannefaer ◽  
D. P. Kerr ◽  
G. W. Dean ◽  
B. G. Hogg
Keyword(s):  
Experimental Data ◽  
Positron Annihilation ◽  
Momentum Distribution ◽  
Positron Lifetime ◽  
Alkali Halides ◽  
Systematic Investigation ◽  
Theoretical Treatment ◽  
Doppler Broadening ◽  
Lifetime Component ◽  
Gamma Irradiated

A systematic investigation of 17 gamma-irradiated alkali halides using positron lifetime and Doppler broadening techniques has been performed. For eight of the alkali halides (NaCl, NaBr, KCl, KBr, KI, RbCl, RbBr, and RbI), a new lifetime with values between 1.0 and 1.3 ns is attributed to positrons trapped in F centres. Despite large F centre concentrations in LiF, LiCl, LiBr, and NaF, no such lifetime component is observed in these samples. Doppler broadening measurements show that in nearly all cases the momentum distribution becomes narrower upon irradiation. The experimental data are discussed in view of a recent theoretical treatment of the positron – F centre problem.

Rate coefficients for the reaction of OH radicals with cis-3-hexene: an experimental and theoretical study

2015 ◽  
Vol 17 (14) ◽  
pp. 8714-8722 ◽  
Author(s):  
Thaís da Silva Barbosa ◽  
Silvina Peirone ◽  
Javier A. Barrera ◽  
Juan P. A. Abrate ◽  
Silvia I. Lane ◽  
...  
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Experimental Rate ◽  
Theoretical Results ◽  
Good Agreement

Microcanonical variational rate coefficients and experimental rate coefficients for the OH addition to cis-3-hexene have been determined. Theoretical results showed a non-Arrhenius profile and good agreement with the experimental data.

scholarly journals Theoretical study of the adsorption of benzene on coinage metals

2014 ◽  
Vol 10 ◽  
pp. 1775-1784 ◽  
Author(s):  
Werner Reckien ◽  
Melanie Eggers ◽  
Thomas Bredow
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Dispersion Correction ◽  
Functional Theory ◽  
Coinage Metals ◽  
Adsorption Energies ◽  
Theoretical Results ◽  
Good Agreement

The adsorption of benzene on the M(111), M(100) and M(110) surfaces of the coinage metals copper (M = Cu), silver (M = Ag) and gold (M = Au) is studied on the basis of density functional theory (DFT) calculations with an empirical dispersion correction (D3). Variants of the Perdew–Burke–Ernzerhof functionals (PBE, RPBE and RevPBE) in combination with different versions of the dispersion correction (D3 and D3(BJ)) are compared. PBE-D3, PBE-D3(BJ) and RPBE-D3 give similar results which exhibit a good agreement with experimental data. RevPBE-D3 and RevPBE-D3(BJ) tend to overestimate adsorption energies. The inclusion of three-center terms (PBE-D3(ABC)) leads to a slightly better agreement with the experiment in most cases. Vertical adsorbate–substrate distances are calculated and compared to previous theoretical results. The observed trends for the surfaces and metals are consistent with the calculated adsorption energies.

Positron Annihilation at Planar Defects in Oxides

2012 ◽  
Vol 733 ◽  
pp. 240-244 ◽  
Author(s):  
Jan Kuriplach ◽  
O. Melikhova ◽  
Jakub Čížek ◽  
I. Procházka ◽  
G. Brauer ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Binding Energy ◽  
Grain Boundary ◽  
Positron Annihilation ◽  
Positron Lifetime ◽  
Theoretical Study ◽  
Stacking Faults ◽  
Calculated Data ◽  
Positron Annihilation Spectroscopy ◽  
Planar Defects

Planar defects may exhibit free volumes which, in principle, are detectable using positron annihilation spectroscopy. In this contribution, we present a preliminary theoretical study of positron trapping at stacking faults in zinc oxide and at a grain boundary in zirconia. In particular, we calculate the positron lifetime and positron binding energy to such defects. In the case of the grain boundary in zirconia, the influence of the yttrium segregation on the GB structure and positron characteristics is also examined. Calculated structural and positron characteristics are critically compared with experimental and other calculated data.

Seeking the Good Fitting Procedure of PALS Polymer Spectra

2008 ◽  
Vol 607 ◽  
pp. 64-66
Author(s):  
Nicolas Laforest ◽  
Jérémie De Baerdemaeker ◽  
Corine Bas ◽  
Charles Dauwe
Keyword(s):  
Experimental Data ◽  
Low Temperature ◽  
Positron Annihilation ◽  
Physical Meaning ◽  
Lifetime Measurements ◽  
Positron Annihilation Lifetime ◽  
Fitting Procedure ◽  
Fitting Procedures ◽  
Blob Model

Positron annihilation lifetime measurements on polymethylmethacrylate (PMMA) at low temperature were performed. Different discrete fitting procedures have been used to analyze the experimental data. It shows that the extracted parameters depend strongly on the fitting procedure. The physical meaning of the results is discussed. The blob model seems to give the best annihilation parameters.

First Stages of Nano-Crystallization of Amorphous Fe75.5Cu1Si12.5B8 Studied by the Positron Annihilation Lifetime Technique

1993 ◽  
Vol 321 ◽  
Author(s):  
A. J. Kruk ◽  
H. Schut ◽  
J. Sietsma ◽  
A. Van Veen
Keyword(s):  
Positron Annihilation ◽  
Crystallization Process ◽  
Positron Lifetime ◽  
Early Stage ◽  
Average Density ◽  
Crystalline Material ◽  
Positron Annihilation Lifetime ◽  
Resistivity Measurements ◽  
Nano Crystalline ◽  
Crystallisation Process

ABSTRACTThe first stages of the nano-crystallization process of amorphous Fe75.5Cu1Nb3Si12.5B8 into a nano-crystalline structure are investigated by the positron annihilation lifetime technique. Samples have been isothermally annealed at 643 K for times varying between 600 and 105 seconds. The positron lifetime spectra have been analyzed allowing for three lifetimes. The shortest and the longest lifetime, τ1 = 150 ± 2 ps and τ3 = 1500–2000 ps respectively, are attributed to annihilation of positrons in the amorphous phase and to the formation and annihilation of ortho-positronium at the surface of the stacked foils and did not change significantly upon the annealing. The intermediate positron lifetime τ2 increased from 324 ps to 387 ps. The intensity of this component increased from 5 to 15%. Comparison with resistivity measurements indicates that the change of this lifetime component occurs at an early stage in the crystallisation process, i.e. when the fraction of crystalline material is on the order of 10−3. The increase of τ2 is attributed to positrons annihilating in a region with lower average density surrounding the small crystallite.

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