Use of a Lowest Intensity 241Am Compton Spectrometer for the Measurement of Directional Compton Profiles of ZnSe

2006 ◽  
Vol 61 (7-8) ◽  
pp. 364-370 ◽  
Author(s):  
Babu Lal Ahuja ◽  
Narayan Lal Heda
Keyword(s):  
Bond Length ◽  
Theoretical Calculations ◽  
The Other ◽  
Energy Bands ◽  
Electron Momentum ◽  
Atomic Orbitals ◽  
Hartree Fock ◽  
Self Consistent ◽  
Scattering Technique ◽  
Small Disc

In this paper we report on electron momentum densities in ZnSe using Compton scattering technique. For the directional measurements we have employed a newly developed 100 mCi 241Am Compton spectrometer which is based on a small disc source with shortest geometry. For the theoretical calculations we have employed a self-consistent Hartree-Fock linear combination of atomic orbitals (HF-LCAO) approach. It is seen that the anisotropy in the measured Compton profiles is well reproduced by our HF-LCAOcalculation and the other available pseudopotential data. The anisotropy in the Compton profiles is explained in terms of energy bands and bond length. - PACS numbers: 13.60.Fz, 78.70. Ck, 78.70.-g

VERTEX CORRECTIONS IN THE NUCLEAR SCHWINGER–DYSON FORMALISM

2002 ◽  
Vol 11 (04) ◽  
pp. 321-333 ◽  
Author(s):  
MASAHIRO NAKANO ◽  
HIROYUKI MATSUURA ◽  
TAISUKE NAGASAWA ◽  
KEN-ICHI MAKINO ◽  
NOBUO NODA ◽  
...  
Keyword(s):  
Field Theory ◽  
Correlation Energy ◽  
Mean Field Theory ◽  
Mean Field ◽  
The Other ◽  
Vertex Correction ◽  
Hartree Fock ◽  
Vertex Corrections ◽  
Negative Correlation Energy ◽  
Self Consistent

We develop the Nuclear Schwinger–Dyson (NSD) formalism to include the effects of ladder diagrams by modifying the vertex. In this extension, the NSD equation sums up both ring diagrams and ladder diagrams self-consistently. The results are compared with mean field theory, Hartree Fock and bare-vertex NSD calculations. It is shown that the vertex correction is important from the following viewpoints. First, the vertex correction greatly modifies the meson propagators, and we can avoid the ghost-pole from meson propagators in a self-consistent way. Secondly, it gives a large negative correlation-energy compared with the other calculations; as a result, it gives a softer equation of state which is preferable according to the experimental data.

A PPP-investigation of Structural Isomerism in Infinite Polyenes

1982 ◽  
Vol 37 (1) ◽  
pp. 28-32 ◽  
Author(s):  
Peter Karadakov ◽  
Obis Castaño
Keyword(s):  
Bond Order ◽  
Analytical Form ◽  
The Other ◽  
Nearest Neighbour ◽  
Bond Orders ◽  
Coulomb Interactions ◽  
Hartree Fock ◽  
Structural Isomerism ◽  
Bond Alternation ◽  
Self Consistent

Abstract It is shown on the grounds of a semiempirical PPP-treatment that for the equidistant eistrans infinite polyene two types of Hartree-Fock solutions are possible-one yielding a cis-transoid and the other a trans-cisoid distribution of nearest-neighbour bond-orders. Relaxing the nuclear framework according to bond-order magnitudes for the bond-alternation wave (BAW) in the equidistant all-trans polyene, resp. for the two solutions for the equidistant cis-trans polyene mentioned above and using repeatedly the Coulson-Golebiewski formula, realistic self-consistent values of bond lengths have been obtained. The calculated energy differences between the investigated isomers are small, predicting almost equal probabilities. The expressions for the PPPwavefunctions are presented in analytical form suitable for further applications. Long-range Coulomb interactions have been accounted for up to convergence of the groundstate energies.

scholarly journals Syntheses and Structures of Novel λ3,λ3-Phosphanylalumanes Fully Bearing Carbon Substituents and Their Substituent Effects

Inorganics ◽  
2019 ◽  
Vol 7 (11) ◽  
pp. 132 ◽  
Author(s):  
Tatsuya Yanagisawa ◽  
Yoshiyuki Mizuhata ◽  
Norihiro Tokitoh
Keyword(s):  
Bond Length ◽  
Theoretical Calculations ◽  
Substituent Effects ◽  
The Other ◽  
Protecting Groups ◽  
Large Contribution ◽  
The Novel ◽  
Single Bond ◽  
Bond Lengths ◽  
Theoretical Results

The novel phosphanylalumanes, Al–P single-bond species, fully bearing carbon protecting groups on aluminum and phosphorus atoms, are synthesized by the reactions of aluminum monohalides [(t-Bu)2AlBr and (C6F5)2AlCl·0.5(toluene)] with Mes2PLi. Regarding the t-Bu system, λ3,λ3-phosphanylalumane is obtained. Concerning the C6F5 system, on the other hand, the corresponding LiCl complex, λ4,λ4-phosphanylalumane, is obtained. The Al–P bond lengths of C6F5-substituted λ3,λ4-, and λ4,λ4-derivatives are much shorter than those of the reported λ3,λ4-phosphanylalumane derivatives and comparable to that observed for the previously reported λ3,λ3-phosphanylalumanes. Theoretical calculations reveal that the binding of the C6F5 groups to Al results in a large contribution of Al and a large s-character in the Al–P bond of phosphanylalumanes. Considering t-Bu-substituted phosphanylalumanes, the Al–P bond lengths reflect the coordination number of Al, showing a longer Al–P bond length in the case of λ4-Al as compared with that of λ3-Al. Combining the structural, spectroscopic, and theoretical results, the t-Bu-substituted λ3,λ3-phosphanylalumane has well separated vacant p orbital and lone pairs, which is suitable for reactivity studies.

Compton Scattering and Electronic Properties of Tungsten Ditelluride

2013 ◽  
Vol 209 ◽  
pp. 107-110 ◽  
Author(s):  
Gunjan Arora ◽  
B.L. Ahuja
Keyword(s):  
Density Functional Theory ◽  
Density Of States ◽  
Density Functional ◽  
Local Density ◽  
Measured Data ◽  
Compton Profile ◽  
Energy Bands ◽  
Functional Theory ◽  
Atomic Orbitals ◽  
Hartree Fock

We report the first ever isotropic experimental Compton profile of tungsten ditelluride using 20 Ci 137Cs Compton spectrometer. To compare our experimental data, we have also computed the Compton profiles, energy bands, density of states and band gap using Hartree-Fock and density functional theory within linear combination of atomic orbitals. The measured data is found to be in better accordance with the generalised gradient approximation of density functional theory than Hartree-Fock and local density approximation. We have discussed the nature of bonding in WTe2 using energy bands and density of states.

scholarly journals Electronic Structure of Copper Antimony Using Compton Scattering Technique

2018 ◽  
Vol 13 (1) ◽  
pp. 167-173
Author(s):  
Baghdad Science Journal
Keyword(s):  
Electronic Structure ◽  
Dft Calculation ◽  
Function Theory ◽  
Momentum Density ◽  
Density Function Theory ◽  
Ionic Model ◽  
Model Calculations ◽  
Electron Momentum ◽  
Atomic Orbitals ◽  
Scattering Technique

In this paper we present the first ever measured experimental electron momentum density of Cu2Sb at an intermediate resolution (0.6 a.u.) using 59.54 keV 241Am Compton spectrometer. The measurements are compared with the theoretical Compton profiles using density function theory (DFT) within a linear combination of an atomic orbitals (LCAO) method. In DFT calculation, Perdew-Burke-Ernzerhof (PBE) scheme is employed to treat correlation whereas exchange is included by following the Becke scheme. It is seen that various approximations within LCAO-DFT show relatively better agreement with the experimental Compton data. Ionic model calculations for a number of configurations (Cu+x/2)2(Sb-x) (0.0≤x≤2.0) are also performed utilizing free atom profiles, the ionic model suggests transfer of 2.0 electrons per Cu atom from 4s state to 5p state of Sb.

A simple quality test for self-consistent-field atomic orbitals

1993 ◽  
Vol 71 (2) ◽  
pp. 175-179 ◽  
Author(s):  
N. Desmarais ◽  
G. Dancausse ◽  
S. Fliszár
Keyword(s):  
Basis Functions ◽  
Quality Test ◽  
Linear Combinations ◽  
Atomic Orbitals ◽  
Hartree Fock ◽  
Consistent Field ◽  
Valence Region ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Finite Linear

A quality test is proposed for SCF atomic orbitals, [Formula: see text] approximated as finite linear combinations of suitable basis functions [Formula: see text] The key is in a function, readily derived from the Hartree–Fock equation [Formula: see text] which is identically zero for true Hartree–Fock spin orbitals and not so for approximate orbitals. In this way, our test measures how closely approximate orbital descriptions approach the true Hartree–Fock limit and thus provides a quality ordering of orbital bases with respect to one another and with respect to that limit, in a scale uniquely defined by the latter. Moreover, this analysis also holds for atomic subspaces of our choice, e.g., the valence region. Examples are offered for representative collections of Slater- and Gaussian-type orbital expansions.

Fully relativistic self-consistent field under a magnetic field

2015 ◽  
Vol 17 (22) ◽  
pp. 14280-14283 ◽  
Author(s):  
Ryan D. Reynolds ◽  
Toru Shiozaki
Keyword(s):  
Magnetic Field ◽  
Atomic Orbitals ◽  
Hartree Fock ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field

Four-component Dirac–Hartree–Fock method with gauge-including atomic orbitals.

An Approximate Treatment of the 1s Hartree Fock Energies in Molecules

1974 ◽  
Vol 29 (5) ◽  
pp. 756-762
Author(s):  
Muthana Shanshal
Keyword(s):  
Ab Initio Calculations ◽  
Periodic Table ◽  
Molecular Orbitals ◽  
The Other ◽  
Valence Shell ◽  
Correlation Effects ◽  
Atomic Orbitals ◽  
Hartree Fock ◽  
Factors Influencing ◽  
Approximate Treatment

Abstract It is found on the basis of Hartree Fock calculations that the inner shell molecular orbitals of compounds that are composed of elements of the first two rows of the periodic table, are described satisfactorily by the corresponding Is atomic orbitals. Such molecular orbitals (MOs) may be substituted in a good approximation by the Is atomic orbitals (AOs). The energy of the localized MOs varies according to the type of bonding in which the atom is participating. The factors influencing the energy values may be classified in two parts; 1) the interaction with the other Is atomic orbitals and nuclii in the molecule, 2) the interaction with the valence shell electrons. Neglecting the correlation effects, both factors are considered by the calculation of the Is orbital energies. The results are compared with ab-Initio calculations done for the same molecules.

Polar Diels-Alder Reactions Under Microwave Irradiation Employing Different Heterocyclic Compounds as Electrophiles

2019 ◽  
Vol 16 (6) ◽  
pp. 527-543 ◽  
Author(s):  
Pedro M.E. Mancini ◽  
Carla M. Ormachea ◽  
María N. Kneeteman
Keyword(s):  
Organic Synthesis ◽  
Heterocyclic Compounds ◽  
Ionic Conduction ◽  
Theoretical Calculations ◽  
Cycloaddition Reaction ◽  
Diels Alder ◽  
The Other ◽  
Conventional Heating ◽  
Protic Ionic Liquids ◽  
Solvent Free Conditions

During the last twenty years, our research group has been working with aromatic nitrosubstituted compounds acting as electrophiles in Polar Diels-Alder (P-DA) reactions with different dienes of diverse nucleophilicity. In this type of reaction, after the cycloaddition reaction, the nitrated compounds obtained as the [4+2] cycloadducts suffer cis-extrusion with the loss of nitrous acid and a subsequent aromatization. In this form, the reaction results are irreversible. On the other hand, the microwave-assisted controlled heating become a powerful tool in organic synthesis as it makes the reaction mixture undergo heating by a combination of thermal effects, dipolar polarization and ionic conduction. As the Diels-Alder (D-A) reaction is one of the most important process in organic synthesis, the microwave (MW) irradiation was applied instead of conventional heating, and this resulted in better yields and shorter reaction times. Several substituted heterocyclic compounds were used as electrophiles and different dienes as nucleophiles. Two experimental situations are involved: one in the presence of Protic Ionic Liquids (PILs) as solvent and the other under solvent-free conditions. The analysis is based on experimental data and theoretical calculations.

Self-consistent tensor effects on nuclear matter systems within a relativistic Hartree-Fock approach

2015 ◽  
Vol 91 (2) ◽  
Author(s):  
Li Juan Jiang ◽  
Shen Yang ◽  
Jian Min Dong ◽  
Wen Hui Long
Keyword(s):  
Nuclear Matter ◽  
Hartree Fock ◽  
Self Consistent
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