ROLE OF HIGHER-MULTIPOLARITY DEFORMATIONS IN THE POTENTIAL ENERGY OF HEAVIEST NUCLEI

2007 ◽  
Vol 16 (02) ◽  
pp. 425-430 ◽  
Author(s):  
M. KOWAL ◽  
A. SOBICZEWSKI
Keyword(s):  
Potential Energy ◽  
General Feature ◽  
Degrees Of Freedom ◽  
Deformation Parameter ◽  
Superheavy Nucleus ◽  
Deformation Space ◽  
Microscopic Approach ◽  
Deformation Parameters ◽  
6 Degrees Of Freedom

Potential energy of the superheavy nucleus 284114 is analyzed in a 6-dimensional deformation space. This space includes two quadrupole, three hexadecapole and one multipolarity-6 deformation parameter. The energy is minimized simultaneously in all 6 degrees of freedom. The analysis is done within a macroscopic-microscopic approach. As in the studies of other superheavy nuclei, the result is found to be very individual for a given nucleus. A more general feature is a small effect of one (γ4) of the hexadecapole deformation parameters on the energy of the nucleus.

DEFORMATIONS OF MULTIPOLARITY SIX AT THE SADDLE POINT OF HEAVIEST NUCLEI

2008 ◽  
Vol 17 (01) ◽  
pp. 265-271 ◽  
Author(s):  
L. SHVEDOV ◽  
S. G. ROHOZIŃSKI ◽  
M. KOWAL ◽  
S. BELCHIKOV ◽  
A. SOBICZEWSKI
Keyword(s):  
Potential Energy ◽  
Saddle Point ◽  
General Type ◽  
Superheavy Nucleus ◽  
Deformation Space ◽  
Microscopic Approach ◽  
Main Attention ◽  
Point Configuration ◽  
Independent Parameters

Saddle-point configuration of heaviest nuclei is studied in a multidimensional deformation space. Main attention is given to the role of the deformation of multipolarity six of a general type, described by four independent parameters. The dependence of the potential energy of a superheavy nucleus on these parameters at the saddle-point configuration is illustrated. The analysis is performed within a macroscopic-microscopic approach.

ROLE OF THE NON-AXIAL OCTUPOLE DEFORMATION IN THE POTENTIAL ENERGY OF HEAVY NUCLEI

2010 ◽  
Vol 19 (04) ◽  
pp. 768-773 ◽  
Author(s):  
P. JACHIMOWICZ ◽  
M. KOWAL ◽  
P. ROZMEJ ◽  
J. SKALSKI ◽  
A. SOBICZEWSKI
Keyword(s):  
Potential Energy ◽  
Large Deformation ◽  
Neutron Number ◽  
Deformation Space ◽  
Heavy Nuclei ◽  
Microscopic Approach ◽  
Large Space ◽  
Global Energy ◽  
Octupole Deformation

Role of the non-axial octupole deformation a32(Y32 + Y3-2) on the potential energy of heavy nuclei is studied in a large deformation space. The study is performed within a macroscopic-microscopic approach. A large region of nuclei with proton number 88 ≤ Z ≤ 112 and neutron number 128 ≤ N ≤ 156 is considered. It is found that while the a32 deformation alone lowers the energy of the nuclei by up to about 3 MeV (for nuclei around 238 Fm ), it has practically no effect on the global energy minima of considered nuclei, when the analysis is done in a large space.

ROLE OF HIGHER MULTIPOLARITY DEFORMATIONS IN THE FISSION-BARRIER HEIGHT OF A SPHERICAL SUPERHEAVY NUCLEUS

2005 ◽  
Vol 14 (03) ◽  
pp. 417-420 ◽  
Author(s):  
I. MUNTIAN ◽  
A. SOBICZEWSKI
Keyword(s):  
Barrier Height ◽  
Superheavy Nucleus ◽  
Spherical Nucleus ◽  
Fission Barrier ◽  
Deformation Space ◽  
Microscopic Approach

Role of the dimension of deformation space used in calculations of the (static) fission-barrier height [Formula: see text] is analyzed for a spherical nucleus. The superheavy nucleus 294116 is taken for the analysis. The study is done within a macroscopic-microscopic approach. It is found that the barrier height [Formula: see text] importantly decreases with increasing dimension of the space.

Phase transition at N = 92 in 158Dy

2016 ◽  
Vol 25 (10) ◽  
pp. 1650076 ◽  
Author(s):  
J. B. Gupta
Keyword(s):  
Phase Transition ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Single Particle ◽  
Degrees Of Freedom ◽  
Energy Surface ◽  
Transition Rates ◽  
Microscopic Approach ◽  
Shape Phase Transition

Beyond the shape phase transition from the spherical vibrator to the deformed rotor regime at [Formula: see text], the interplay of [Formula: see text]- and [Formula: see text]-degrees of freedom becomes important, which affects the relative positions of the [Formula: see text]- and [Formula: see text]-bands. In the microscopic approach of the dynamic pairing plus quadrupole model, a correlation of the strength of the quadrupole force and the formation of the [Formula: see text]- and [Formula: see text]-bands in [Formula: see text]Dy is described. The role of the potential energy surface is illustrated. The [Formula: see text] transition rates in the lower three [Formula: see text]-bands and the multi-phonon bands with [Formula: see text] and [Formula: see text] are well reproduced. The absolute [Formula: see text] [Formula: see text] serves as a good measure of the quadrupole strength. The role of the single particle Nilsson orbits is also described.

Nonaxial hexadecapole deformation effects on the fission barrier

2016 ◽  
Vol 25 (08) ◽  
pp. 1650047 ◽  
Author(s):  
A. Kardan ◽  
S. Nejati
Keyword(s):  
Heavy Nucleus ◽  
Degree Of Freedom ◽  
Fission Barrier ◽  
Deformation Space ◽  
Microscopic Approach ◽  
Barrier Heights ◽  
Deformation Parameters

Fission barrier of the heavy nucleus [Formula: see text]Cf is analyzed in a multi-dimensional deformation space. This space includes two quadrupole ([Formula: see text]) and three hexadecapole deformation ([Formula: see text]) parameters. The analysis is performed within an unpaired macroscopic–microscopic approach. Special attention is given to the effects of the axial and non-axial hexadecapole deformation shapes. It is found that the inclusion of the nonaxial hexadecapole shapes does not change the fission barrier heights, so it should be sufficient to minimize the energy in only one degree of freedom in the hexadecapole space [Formula: see text]. The role of hexadecapole deformation parameters is also discussed on the Lublin–Strasbourg drop (LSD) macroscopic and the Strutinsky shell energies.

SADDLE-POINT SHELL EFFECTS OF HEAVIEST NUCLEI

2008 ◽  
Vol 17 (01) ◽  
pp. 259-264 ◽  
Author(s):  
M. KOWAL ◽  
L. SHVEDOV ◽  
A. SOBICZEWSKI
Keyword(s):  
Potential Energy ◽  
Saddle Point ◽  
Equilibrium Point ◽  
Ground State ◽  
Shell Correction ◽  
Deformation Space ◽  
Microscopic Approach ◽  
Shell Effects ◽  
State Point

The shell correction to the potential energy of heaviest nuclei is studied in a multidimensional deformation space. The correction is calculated at the saddle point of the nuclei and compared with that obtained at the equilibrium (ground state) point. Although generally much smaller than at the equilibrium point, the correction at the saddle point is still found to be large and significant. The analysis is performed within a macroscopic-microscopic approach.

SADDLE-POINT SHAPES OF HEAVY AND SUPERHEAVY NUCLEI

2008 ◽  
Vol 17 (01) ◽  
pp. 168-176 ◽  
Author(s):  
A. SOBICZEWSKI ◽  
M. KOWAL ◽  
L. SHVEDOV
Keyword(s):  
Potential Energy ◽  
Saddle Point ◽  
Large Deformation ◽  
Ground State ◽  
Neutron Number ◽  
Superheavy Nuclei ◽  
Deformation Space ◽  
Microscopic Approach ◽  
Main Attention ◽  
Heavy And Superheavy Nuclei

The potential energy of the heaviest nuclei is analyzed in a large deformation space. The main attention is given to shapes of these nuclei at their saddle point and to the comparison of these shapes with those at the ground state. The shapes are analyzed in a 10-dimensional deformation space. The analysis is performed within a macroscopic-microscopic approach. Even-even nuclei with proton number 98 ≤ Z ≤ 126 and neutron number 138 ≤ N ≤ 194 are considered.

scholarly journals Dragondrop: a novel passive mechanism for aerial righting in the dragonfly

2021 ◽  
Vol 288 (1944) ◽  
pp. 20202676
Author(s):  
Samuel T. Fabian ◽  
Rui Zhou ◽  
Huai-Ti Lin
Keyword(s):  
Degrees Of Freedom ◽  
Inverse Dynamics ◽  
Wind Tunnel Experiments ◽  
Kinematic Data ◽  
Passive Mechanism ◽  
Roll Axis ◽  
Lower Moment ◽  
Capture Techniques ◽  
6 Degrees Of Freedom

Dragonflies perform dramatic aerial manoeuvres when chasing targets but glide for periods during cruising flights. This makes dragonflies a great system to explore the role of passive stabilizing mechanisms that do not compromise manoeuvrability. We challenged dragonflies by dropping them from selected inverted attitudes and collected 6-degrees-of-freedom aerial recovery kinematics via custom motion capture techniques. From these kinematic data, we performed rigid-body inverse dynamics to reconstruct the forces and torques involved in righting behaviour. We found that inverted dragonflies typically recover themselves with the shortest rotation from the initial body inclination. Additionally, they exhibited a strong tendency to pitch-up with their head leading out of the manoeuvre, despite the lower moment of inertia in the roll axis. Surprisingly, anaesthetized dragonflies could also complete aerial righting reliably. Such passive righting disappeared in recently dead dragonflies but could be partially recovered by waxing their wings to the anaesthetised posture. Our kinematics data, inverse dynamics model and wind-tunnel experiments suggest that the dragonfly's long abdomen and wing posture generate a rotational tendency and passive attitude recovery mechanism during falling. This work demonstrates an aerodynamically stable body configuration in a flying insect and raises new questions in sensorimotor control for small flying systems.

Driving Torsion Scans with Wavefront Propagation

2020 ◽  
Author(s):  
Yudong Qiu ◽  
Daniel Smith ◽  
Chaya Stern ◽  
mudong feng ◽  
Lee-Ping Wang
Keyword(s):  
Potential Energy ◽  
Force Field ◽  
Degrees Of Freedom ◽  
Computational Cost ◽  
Initial Guess ◽  
Field Development ◽  
Force Field Development ◽  
Wavefront Propagation ◽  
Open Source Software Package

<div>The parameterization of torsional / dihedral angle potential energy terms is a crucial part of developing molecular mechanics force fields.</div><div>Quantum mechanical (QM) methods are often used to provide samples of the potential energy surface (PES) for fitting the empirical parameters in these force field terms.</div><div>To ensure that the sampled molecular configurations are thermodynamically feasible, constrained QM geometry optimizations are typically carried out, which relax the orthogonal degrees of freedom while fixing the target torsion angle(s) on a grid of values.</div><div>However, the quality of results and computational cost are affected by various factors on a non-trivial PES, such as dependence on the chosen scan direction and the lack of efficient approaches to integrate results started from multiple initial guesses.</div><div>In this paper we propose a systematic and versatile workflow called \textit{TorsionDrive} to generate energy-minimized structures on a grid of torsion constraints by means of a recursive wavefront propagation algorithm, which resolves the deficiencies of conventional scanning approaches and generates higher quality QM data for force field development.</div><div>The capabilities of our method are presented for multi-dimensional scans and multiple initial guess structures, and an integration with the MolSSI QCArchive distributed computing ecosystem is described.</div><div>The method is implemented in an open-source software package that is compatible with many QM software packages and energy minimization codes.</div>

On the Use of Quantum Thermal Bath in Unimolecular Fragmentation Simulations

2019 ◽  
Author(s):  
Riccardo Spezia ◽  
Hichem Dammak
Keyword(s):  
Degrees Of Freedom ◽  
Molecular Simulations ◽  
Zero Point ◽  
Thermal Bath ◽  
Unimolecular Dissociation ◽  
Point Energy ◽  
Rotational Degrees Of Freedom ◽  
The Difference ◽  
Nuclear Effects

<div> <div> <div> <p>In the present work we have investigated the possibility of using the Quantum Thermal Bath (QTB) method in molecular simulations of unimolecular dissociation processes. Notably, QTB is aimed in introducing quantum nuclear effects with a com- putational time which is basically the same as in newtonian simulations. At this end we have considered the model fragmentation of CH4 for which an analytical function is present in the literature. Moreover, based on the same model a microcanonical algorithm which monitor zero-point energy of products, and eventually modifies tra- jectories, was recently proposed. We have thus compared classical and quantum rate constant with these different models. QTB seems to correctly reproduce some quantum features, in particular the difference between classical and quantum activation energies, making it a promising method to study unimolecular fragmentation of much complex systems with molecular simulations. The role of QTB thermostat on rotational degrees of freedom is also analyzed and discussed. </p> </div> </div> </div>

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