Shape isomerism and magicity in Ni isotopes

2021 ◽  
pp. 2150128
Author(s):  
Tabassum Naz ◽  
Shakeb Ahmad ◽  
H. Abusara
Keyword(s):  
Meson Exchange ◽  
Present Calculation ◽  
Theoretical Studies ◽  
Shell Closure ◽  
Level Crossing ◽  
Hartree Fock ◽  
Tensor Parameter ◽  
Experimental Findings ◽  
Made In ◽  
Neutron Shell Closure

A systematic study of shapes in Ni [Formula: see text] isotopes has been made in the Relativistic–Hartree–Bogoliubov (RHB) formalism with two types of density-dependent NN interactions which are based on the range of meson-exchange. The constraint calculations assuming the axial and triaxial-symmetry predict the shape isomerism in the case of [Formula: see text] isotopes. Significant jumps at [Formula: see text] in the binding energy per nucleon (BE/A) and in the [Formula: see text] correspond to the neutron shell closure, and [Formula: see text] as doubly magic nuclei. The present calculation supports the recently reported calculations using the non-relativistic Hartree–Fock (HF) Skyrme SIII [1] interaction predicting the importance of tensor parameter in order to reproduce the experimental findings of the proton level crossing at [Formula: see text]. The results obtained are in agreement with experiment and with other theoretical studies.

ALPHA-DECAY STUDIES ON 130-153Eu NUCLEI

2013 ◽  
Vol 22 (11) ◽  
pp. 1350081 ◽  
Author(s):  
K. P. SANTHOSH ◽  
B. PRIYANKA
Keyword(s):  
Experimental Data ◽  
Potential Model ◽  
Alpha Decay ◽  
Shell Closure ◽  
Proximity Potential ◽  
Deformed Nuclei ◽  
Neutron Shell ◽  
Good Agreement ◽  
Neutron Shell Closure

The alpha-decay half-lives of the 24 isotopes of Eu (Z = 63) nuclei in the region 130≤A≤153, have been studied systematically within the Coulomb and proximity potential model (CPPM). We have modified the assault frequency and re-determined the half-lives and they show a better agreement with the experimental value. We have also done calculations on the half-lives within the recently proposed Coulomb and proximity potential model for deformed nuclei (CPPMDN). The computed half-lives are compared with the experimental data and they are in good agreement. Using our model, we could also demonstrate the influence of the neutron shell closure at N = 82, in both parent and daughter nuclei, on the alpha-decay half-lives.

scholarly journals THE FREE RADICAL BRO MINA TION OF ETHYL PYRIDAZINES: THEORETICAL STUDIES

2014 ◽  
Vol 22 (22) ◽  
pp. 53-60
Author(s):  
I. A. ADEJORO ◽  
R. O. Ogede ◽  
C. U. Ibeji ◽  
O. O. Adeboye
Keyword(s):  
Free Radical ◽  
Rapid Method ◽  
Computational Methods ◽  
Theoretical Studies ◽  
Hartree Fock ◽  
Radical Bromination ◽  
Total Energies ◽  
Pyridazine Derivatives ◽  
Semi Empirical

Theoretical studies on free radical bromination by N-bromosuccinimide were carried out on a range of ethyl-3-methoxy-pyridazine derivatives. The investigations of these reactions performed, in order to develop a convenient and rapid theoretical means of predicting selectivity. The geometry optimizations of the total energies of the reactants and the products were calculated using Semi-empirical; AMI, MNDO, PM3 e Hartree Fock, HF3- 21 G computational methods. The calculation performed using PM3 Hamiltonian gave the best qualitative predictions, thus providing a rapid method for the selectivity of the reactions used in the synthesis of novel heterocyclic analogs of neurotransmitters.

scholarly journals An ab initio Hartree-Fock Investigation of Endohedral Sc@C82

1998 ◽  
Vol 53 (9) ◽  
pp. 801-805 ◽  
Author(s):  
Andrea Gruß ◽  
Michael C. Böhm ◽  
Joachim Schulte ◽  
Klaus-Peter Dinse
Keyword(s):  
Ab Initio ◽  
Minimum Energy ◽  
Fullerene Cage ◽  
Site Symmetry ◽  
Fold Axis ◽  
Hartree Fock ◽  
Endohedral Complex ◽  
Experimental Findings ◽  
Ab Initio Hf ◽  
Hf Calculations

Abstract The electronic structure of endohedral Sc@C82 with a C82 cage of C2v symmetry has been studied by ab initio Hartree-Fock (HF) calculations. The optimized position of Sc in the configuration of minimum energy is predicted to be on the two-fold axis of the fullerene cage. In the corresponding configuration Sc is above the center of a hexagon of site symmetry C2 . This structure of C2v symmetry is nearly degenerate with Cs and Ct structures with Sc slightly displaced from the center of the coordinated hexagon. The binding energy of the endohedral complex is larger than 3.55 eV. The ab initio HF data of the C2v topoisomer of the fullerene unit are compared with new experimental findings and HF results derived for the 3(C2) topoisomer of the C82 cage.

scholarly journals Nuclear shapes: Quest for triaxiality in 86Ge and the shape of 98Zr

2018 ◽  
Vol 178 ◽  
pp. 02013 ◽  
Author(s):  
V. Werner ◽  
M. Lettmann ◽  
C. Lizarazo ◽  
W. Witt ◽  
D. Cline ◽  
...  
Keyword(s):  
Phase Transition ◽  
Nuclear Structure ◽  
Shape Coexistence ◽  
Shell Closure ◽  
Structural Effects ◽  
Triaxial Deformation ◽  
Rich Variety ◽  
Shell Closures ◽  
Shape Phase Transition ◽  
Neutron Shell Closure

The region of neutron-rich nuclei above the N = 50 magic neutron shell closure encompasses a rich variety of nuclear structure, especially shapeevolutionary phenomena. This can be attributed to the complexity of sub-shell closures, their appearance and disappearance in the region, such as the N = 56 sub shell or Z = 40 for protons. Structural effects reach from a shape phase transition in the Zr isotopes, over shape coexistence between spherical, prolate, and oblate shapes, to possibly rigid triaxial deformation. Recent experiments in this region and their main physics viewpoints are summarized.

scholarly journals Newton as an experimenter

1943 ◽  
Vol 181 (986) ◽  
pp. 244-250
Keyword(s):  
Experimental Work ◽  
Furnace Operation ◽  
The Other ◽  
Theoretical Studies ◽  
Other Hand ◽  
Made In ◽  
Grinding And Polishing ◽  
At Home

The duty has been assigned to me of telling you something about Newton as an experimentalist. As the result of a study of what is known of his history, it seems to me that among his various intellectual pursuits experiment was his first love and the love to which he was most constant. Strange though it be, he seems in some moods to have doubted whether his theoretical studies were worth while, and I do not recall any case where he expressed himself enthusiastically about them. On the other hand, he speaks of his optical work as ‘The oddest if not the most considerable detection which has hitherto been made in the operation of nature.’ Newton loved the mechanical side of experimental work. As a boy he constructed sundials, and, what is more, fixed one of them into the side of the house effectually enough for it to be there a century later. A notebook of his boyhood shows him assiduous in collecting recipes for various kinds of drawing materials, and he notes methods of performing some (rather nasty) conjuring tricks. Later on, when he is making his reflecting telescope, it is obvious that he is a skilled amateur mechanic, at home in furnace operation. He builds his own brick furnace, prepares speculum metal, and is apparently more successful than the professional opticians of the time in grinding and polishing it to a satisfactory spherical figure. (The days of parabolizing were not yet.) It was not until a good many years later that they were able to put such instruments on the market.

scholarly journals Theory of correlated insulating behaviour and spin-triplet superconductivity in twisted double bilayer graphene

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Jong Yeon Lee ◽  
Eslam Khalaf ◽  
Shang Liu ◽  
Xiaomeng Liu ◽  
Zeyu Hao ◽  
...  
Keyword(s):  
Displacement Field ◽  
Twist Angle ◽  
Vertical Displacement ◽  
Bilayer Graphene ◽  
Magic Angle ◽  
Hartree Fock ◽  
Flat Bands ◽  
Half Filling ◽  
Spin Triplet ◽  
Experimental Findings

AbstractTwo graphene monolayers twisted by a small magic angle exhibit nearly flat bands, leading to correlated electronic states. Here we study a related but different system with reduced symmetry - twisted double bilayer graphene (TDBG), consisting of two Bernal stacked bilayer graphenes, twisted with respect to one another. Unlike the monolayer case, we show that isolated flat bands only appear on application of a vertical displacement field. We construct a phase diagram as a function of twist angle and displacement field, incorporating interactions via a Hartree-Fock approximation. At half-filling, ferromagnetic insulators are stabilized with valley Chern number $${C}_{{\rm{v}}}=\pm 2$$Cv=±2. Upon doping, ferromagnetic fluctuations are argued to lead to spin-triplet superconductivity from pairing between opposite valleys. We highlight a novel orbital effect arising from in-plane fields plays an important role in interpreting experiments. Combined with recent experimental findings, our results establish TDBG as a tunable platform to realize rare phases in conventional solids.

Experimental and theoretical studies of the mica polymorphs

1956 ◽  
Vol 31 (234) ◽  
pp. 209-235 ◽  
Author(s):  
J. V. Smith ◽  
H. S. Yoder
Keyword(s):  
Growth Mechanism ◽  
Theoretical Study ◽  
Dominant Role ◽  
Spiral Growth ◽  
Theoretical Studies ◽  
X Ray ◽  
Layer Cell ◽  
Triclinic Structure ◽  
Experimental And Theoretical Studies ◽  
Made In

SummaryAn experimental and theoretical study has been made in order to determine the number and the structure of the possible polymorphs and to determine the structural relations between them. The simplest structures are 1M, 2M1, 2M2, 3T, 20, and 6H polymorphs, and more complicated types can be developed. Some of the previously described polymorphs were not contained in the theoretical list and were re-examined. The 6M structure was found to be a 2M2 polymorph, the 6-layer triclinic type was found to be a 2M1 polymorph, and the 3M structure was shown to be a 3T type. The 24-layer triclinic structure could be described on a simpler 8-layer cell. This type together with a new 12-layer monoclinic structure, as well as other structures of higher periodicity, presumably consists of complex stacking and results from spiral-growth mechanism. Two extreme types of layer-disordered crystals may be built and a disorder of individual ions may also occur. Single stacking faults result in twinned crystals. A new twin relation (180° rotation about the [100] axis) has been recognized. Twenty specimens from extreme geological environments have been examined in order to evaluate the control of environment on the stacking. The type of stacking could not be attributed solely to the influence of pressure and temperature. Composition appears to play a dominant role in the type of stacking, and semi-quantitative structural arguments appear to support this contention. The influence of growth mechanism is discussed. A scheme for the identification of the mica polymorphs by X-ray powder and single-crystal methods is given.

An Engineering Basis for Establishing Radiographic Acceptance Standards for Porosity in Steel Weldments

1965 ◽  
Vol 87 (4) ◽  
pp. 887-893 ◽  
Author(s):  
H. Greenberg
Keyword(s):  
Stress Concentration ◽  
Nondestructive Testing ◽  
Pressure Vessel ◽  
Maximum Size ◽  
Theoretical Studies ◽  
Concentration Effects ◽  
Close Proximity ◽  
Testing Techniques ◽  
Steel Welds ◽  
Made In

Radiographic acceptance standards, such as those found in the ASME Unfired Pressure Vessel Code are critically reviewed. Limits on the size and distribution of porosity in steel welds are analyzed from the viewpoint of susceptibility to failure in service. In large part, present standards for porosity appear to have been established on a “good workmanship” basis rather than on setting sound conservative limits for the maximum size, and distribution of flaws which can be tolerated without decreasing the reliability of the product. Radiographic acceptance standards in use today do not reflect the significant advances being made in (1) the fracture mechanics approach to designing for prevention of failure; (2) theoretical studies of the stress-concentration effects of holes in close proximity to one another; and (3) the possible use of complementary nondestructive testing techniques. Considerable emphasis is placed on the proposition that radiographic acceptance standards for weldments must be designed specifically for each particular application. Considerations applicable to welds in the 120-in-dia rocket motor case are cited as an example of how standards for acceptable porosity and inclusions can be established.

scholarly journals Ab initio and first principles theoretical investigations of triplet–triplet fluorescence in trimethylenemethane biradicals

RSC Advances ◽  
2016 ◽  
Vol 6 (87) ◽  
pp. 83668-83672 ◽  
Author(s):  
Yasunori Matsui ◽  
Kosuke Usui ◽  
Hiroshi Ikeda ◽  
Stephan Irle
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Studies ◽  
Functional Theory ◽  
Hartree Fock ◽  
Theoretical Investigations

Theoretical studies on triplet–triplet (T1 → T0) fluorescence of the arylated trimethylenemethane (TMM) biradicals, 32˙˙, were carried out using post-Hartree–Fock ab initio and various first principles density functional theory methods.

Paramagnetic impurities in an itinerant antiferromagnet. Theory

1969 ◽  
Vol 47 (5) ◽  
pp. 477-487 ◽  
Author(s):  
S. N. Behera ◽  
K. S. Viswanathan
Keyword(s):  
Density Of States ◽  
Energy Gap ◽  
Impurity Site ◽  
Atom Ratio ◽  
Hartree Fock ◽  
Paramagnetic Impurities ◽  
Spin Dependent Scattering ◽  
Experimental Findings ◽  
Gap Parameter ◽  
Theory And Experiment

The effects of 3-d paramagnetic impurities in an itinerant antiferromagnetic metal are investigated using the Wolff–Clogston model. The changes in the Néel temperature TN, the energy-gap parameter, and the density of states are evaluated in the Hartree–Fock approximation and in the lowest order in the impurity concentration. The results on the changes in TN are compared with the experimental findings on V, Mn, Fe, Co, Ni, Mo, and W impurities in chromium. The agreement between theory and experiment suggests that the changes in TN are essentially due to three mechanisms: (a) the effect due to changes in the electron–atom ratio, (b) the spin-dependent scattering due to paramagnetic impurities, and (c) the changes in the intra-atomic coulomb potential at the impurity site. In the case of Mo and W, the last effect explains the observed decrease in TN in Cr.

Sign in / Sign up

Export Citation Format

Share Document