MICROSCOPIC ANALYSIS OF SHAPE EVOLUTION IN Mo ISOTOPES

2013 ◽  
Vol 28 (30) ◽  
pp. 1350134 ◽  
Author(s):  
M. R. OUDIH ◽  
M. FELLAH ◽  
N. H. ALLAL ◽  
N. BENHAMOUDA
Keyword(s):  
Potential Energy Surfaces ◽  
Density Functional ◽  
Microscopic Analysis ◽  
Shape Evolution ◽  
Energy Density Functional ◽  
Hartree Fock ◽  
Bogoliubov Theory ◽  
Pairing Correlations ◽  
Energy Surfaces ◽  
Mo Isotopes

The shape evolution of even–even Mo isotopes from the line of stability up to the two-neutron drip-line is investigated within the self-consistent Hartree–Fock–Bogoliubov theory in both the axial and triaxial symmetries. The Skyrme energy density functional SLy4 has been considered in the particle-hole channel, while the zero range delta-interaction has been employed in the particle–particle channel. In order to correctly treat the pairing correlations, a particle-number projection was carried out by the Lipkin–Nogami (LN) method. The two-neutron separation energies and root-mean-square (rms) charge radii are investigated and compared with available experimental data. The evolution of the potential energy surfaces in the (β, γ) deformation plane is presented and discussed. In addition, the obtained ground state deformation parameters are compared to those obtained by other models.

scholarly journals Impact of Approximate DFT Density Delocalization Error on Potential Energy Surfaces in Transition Metal Chemistry

2019 ◽  
Author(s):  
Fang Liu ◽  
Heather Kulik
Keyword(s):  
Transition Metal ◽  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Spin States ◽  
Transition Metal Chemistry ◽  
Metal Chemistry ◽  
Hartree Fock ◽  
Higher Spin ◽  
Energy Surfaces

For approximate density functional theory (DFT) to be useful in catalytic applications of transition metal complexes, modeling strategies must simultaneously address electronic, geometric, and energetic properties of the relevant species. We show that for representative transition metal triatomics (MO<sub>2</sub>, where M = Cr, Mn, Fe, Co, or Ni) and related diatomics the incorporation of Hartree–Fock (HF) exchange in most cases improves the properties of the Born–Oppenheimer potential energy surface (PES) with respect to accurate experimental or CCSD(T) references. We rationalize this observation by noting reduced delocalization obtained with hybrid functionals (20–40% HF exchange), as evidenced by reduced hybridization of non-bonding orbitals and increases in metal partial charges. Although we show that the optimal exchange fraction is both property and system specific, incorporating HF exchange synergistically improves properties of density, structure, and energetics within a single PES characterized by moderately covalent bonding. The same improvement is not observed in the ordering of MO2 spin states, as good agreement of semi-local DFT spin state ordering is worsened by over stabilization of higher spin states when HF exchange is added. More work is needed to understand minimal functional forms capable of improving multiple properties with respect to semi-local DFT descriptions of transition metal chemistry.

scholarly journals Impact of Approximate DFT Density Delocalization Error on Potential Energy Surfaces in Transition Metal Chemistry

2019 ◽  
Author(s):  
Fang Liu ◽  
Heather Kulik
Keyword(s):  
Transition Metal ◽  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Spin States ◽  
Transition Metal Chemistry ◽  
Metal Chemistry ◽  
Hartree Fock ◽  
Higher Spin ◽  
Energy Surfaces

For approximate density functional theory (DFT) to be useful in catalytic applications of transition metal complexes, modeling strategies must simultaneously address electronic, geometric, and energetic properties of the relevant species. We show that for representative transition metal triatomics (MO<sub>2</sub>, where M = Cr, Mn, Fe, Co, or Ni) and related diatomics the incorporation of Hartree–Fock (HF) exchange in most cases improves the properties of the Born–Oppenheimer potential energy surface (PES) with respect to accurate experimental or CCSD(T) references. We rationalize this observation by noting reduced delocalization obtained with hybrid functionals (20–40% HF exchange), as evidenced by reduced hybridization of non-bonding orbitals and increases in metal partial charges. Although we show that the optimal exchange fraction is both property and system specific, incorporating HF exchange synergistically improves properties of density, structure, and energetics within a single PES characterized by moderately covalent bonding. The same improvement is not observed in the ordering of MO2 spin states, as good agreement of semi-local DFT spin state ordering is worsened by over stabilization of higher spin states when HF exchange is added. More work is needed to understand minimal functional forms capable of improving multiple properties with respect to semi-local DFT descriptions of transition metal chemistry.

AN INVESTIGATION ON SHAPE EVOLUTION OF Ti ISOTOPES WITH HARTREE–FOCK–BOGOLIUBOV THEORY

2012 ◽  
Vol 27 (28) ◽  
pp. 1250162 ◽  
Author(s):  
TUNCAY BAYRAM
Keyword(s):  
Potential Energy ◽  
Single Particle ◽  
Potential Energy Curves ◽  
Shape Evolution ◽  
Shape Transition ◽  
Hartree Fock ◽  
Bogoliubov Theory ◽  
Unstable Nuclei

Constrained Hartree–Fock–Bogoliubov theory with SLy4 and SLy5 Skyrme forces is used to investigate the shape transition between spherical and γ-unstable nuclei in 38–66 Ti . By examining potential energy curves and neutron single-particle levels of even–even Ti isotopes, 46,52,60 Ti are suggested as possible candidates of the nuclei with E(5) symmetry.

scholarly journals The ANI-1ccx and ANI-1x Data Sets, Coupled-Cluster and Density Functional Theory Properties for Molecules

2020 ◽  
Author(s):  
Justin S. Smith ◽  
Roman Zubatyuk ◽  
Benjamin T. Nebgen ◽  
Nicholas Lubbers ◽  
Kipton Barros ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Atomic Charge ◽  
Density Functional Theory Calculations ◽  
Coupled Cluster ◽  
Data Sets ◽  
Data Set ◽  
Functional Theory ◽  
Energy Surfaces

<p>Maximum diversification of data is a central theme in building generalized and accurate machine learning (ML) models. In chemistry, ML has been used to develop models for predicting molecular properties, for example quantum mechanics (QM) calculated potential energy surfaces and atomic charge models. The ANI-1x and ANI-1ccx ML-based eneral-purpose potentials for organic molecules were developed through active learning; an automated data diversification process. Here, we describe the ANI-1x and ANI-1ccx data sets. To demonstrate data set diversity, we visualize them with a dimensionality reduction scheme, and contrast against existing data sets. The ANI-1x data set contains multiple QM properties from 5M density functional theory calculations, while the ANI-1ccx data set contains 500k data points obtained with an accurate CCSD(T)/CBS extrapolation. Approximately 14 million CPU core-hours were expended to generate this data. Multiple QM properties from density functional theory and coupled cluster are provided: energies, atomic forces, multipole moments, atomic charges, and more. We provide this data to the community to aid research and development of ML models for chemistry.</p>

scholarly journals Migration of Zeolite-Encapsulated Pt and Au Under Reducing Atmospheres

2021 ◽  
Author(s):  
Dianwei Hou ◽  
Christopher Heard
Keyword(s):  
Monte Carlo ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Noble Metals ◽  
Kinetic Monte Carlo ◽  
Pore System ◽  
Kinetic Monte Carlo Simulations ◽  
Zeolite Lta ◽  
Metal Migration ◽  
Energy Surfaces

Unbiased density functional global optimisation calculations, followed by kinetic Monte Carlo simulations are used to enumerate the potential energy surfaces for migration of noble metals Pt and Au inside the pore system of siliceous zeolite LTA. The effects of reducing adsorbates CO and H2 are determined. It is found that the two metals differ significantly in the strength and type of interaction with the framework, with strong, framework breaking interactions between Pt and and the zeolite, but only weak dispersive interactions between Au and the zeolite. Adsorbates are found to dramatically interfere with Pt-framework binding, leading to poorer atom-trapping, enhanced metal migration and faster equilibration.

scholarly journals Investigation of the nuclear structure of 84-108Mo isotopes using Skyrme-Hartree-Fock method

2019 ◽  
Vol 13 (26) ◽  
pp. 1-11
Author(s):  
Ali A. Alzubadi
Keyword(s):  
Density Functional ◽  
Good Description ◽  
Mean Field ◽  
Nucleon Nucleon ◽  
Effective Density ◽  
Skin Thickness ◽  
Neutron Skin ◽  
Energy Density Functional ◽  
Charge Densities ◽  
Hartree Fock

Over the last few decades the mean field approach using selfconsistentHaretree-Fock (HF) calculations with Skyrme effectiveinteractions have been found very satisfactory in reproducingnuclear properties for both stable and unstable nuclei. They arebased on effective energy-density functional, often formulated interms of effective density-dependent nucleon–nucleon interactions.In the present research, the SkM, SkM*, SI, SIII, SIV, T3, SLy4,Skxs15, Skxs20 and Skxs25 Skyrme parameterizations have beenused within HF method to investigate some static and dynamicnuclear ground state proprieties of 84-108Mo isotopes. In particular,the binding energy, proton, neutron, mass and charge densities andcorresponding root mean square radius, neutron skin thickness andcharge form factor are calculated by using this method with theSkyrme parameterizations mentioned above. The calculated resultsare compared with the available experimental data. Calculationsshow that the Skyrme–Hartree–Fock (SHF) theory with aboveforce parameters provides a good description on Mo isotopes.

Microscopic description of the fusion excitation function of 32,36S+90,94,96Zr

2020 ◽  
Vol 29 (07) ◽  
pp. 2050046
Author(s):  
M. Rashdan ◽  
T. A. Abdel-Karim
Keyword(s):  
Excitation Function ◽  
Excited States ◽  
Density Functional ◽  
Neutron Density ◽  
Energy Density Functional ◽  
Hartree Fock ◽  
Density Distributions ◽  
Text Interaction ◽  
Good Agreement

The fusion excitation function for the systems [Formula: see text]S+[Formula: see text]Zr is investigated using a microscopic internuclear potential derived from Skyrme energy density functional. The inputs in this approach are the proton and neutron density distributions of the interacting nuclei, which are derived from Skyrme–Hartree–Fock calculations. The SkM[Formula: see text] interaction is used in the calculation of the nuclear densities as well as the internuclear potential. The coupling to low lying inelastic excited states of target and projectile is considered. The role of the neutron transfer is discussed, where it is considered through the CCFULL model calculation. A good agreement with the experimental data is obtained without adjustable parameters.

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