Dynamics of nuclear recoil: QM-MD simulations ofmodel systems following β-decay

2021 ◽  
Author(s):  
Rasmus Fromsejer ◽  
Kurt V Mikkelsen ◽  
Lars Hemmingsen
Keyword(s):  
Daughter Nucleus ◽  
Md Simulations ◽  
Nuclear Recoil ◽  
Recoil Energy ◽  
Nuclear Decay ◽  
Β Decay ◽  
Chemical Systems

The kinetic recoil energy received by the daughter nucleus in a nuclear decay is often large enough to affect the structure around the nucleus in chemical systems. The coinciding element change...

scholarly journals The PANDORA project: an experimental setup for measuring in-plasma β-decays of astrophysical interest

2020 ◽  
Vol 227 ◽  
pp. 01013
Author(s):  
David Mascali ◽  
Maurizio Busso ◽  
Alberto Mengoni ◽  
Simone Amaducci ◽  
Castro Giuseppe ◽  
...  
Keyword(s):  
Nuclear Astrophysics ◽  
Charge State Distribution ◽  
Decay Rates ◽  
Nuclear Decay ◽  
Early Solar System ◽  
State Distribution ◽  
Β Decay ◽  
Plasma Trap ◽  
First Time ◽  
Magnetic Plasma

Experiments performed on Storage Rings have shown that lifetimes of beta-radionuclides can change dramatically as a function of theionization state. PANDORA (Plasmas for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry) aims at measuring, for the first time, nuclear β-decay rates in stellar-like conditions, especially for radionuclides involved in nuclear-astrophysics processes (BBN, s- processing, CosmoChronometers, Early Solar System formation). Compact magnetic plasma traps, where plasmas reach density ne~10n-1014 cm-3, and temperature Te~0.1-30 keV, are suitable for such studies. The decay rates can be measured as a function of the charge state distribution of the inplasma ions. The collaboration is now designing the plasma trap able to reach the needed plasma densities, temperatures and charge states distributions. A first list of radioisotopes, including tens of physics cases of potential interest is now available. Possible physics cases include, among the others, 2°4Tl, 63Ni, 6°Co, 171Tm, 147Pm, 85Kr, 176Lu and the pairs 187Re-187Os and 87Sr-87Rb, which play a crucial role as cosmo-clock. Physics cases are now under evaluation in terms of lifetime measurements feasibility in a plasma trap.

Capabilities of chemical simulation methods in the elucidation of structure and dynamics of solutions

2008 ◽  
Vol 80 (6) ◽  
pp. 1195-1210 ◽  
Author(s):  
Thomas S. Hofer ◽  
Andreas B. Pribil ◽  
Bernhard R. Randolf
Keyword(s):  
High Performance ◽  
Md Simulations ◽  
Quantum Mechanical ◽  
Chemical Systems ◽  
Simulation Techniques ◽  
Chemical Simulation ◽  
Charge Field ◽  
Performance Computing ◽  
Structure Breaking ◽  
Mechanical Charge

As a result of recent methodological developments in connection with enhanced computational capacity, theoretical methods have become increasingly valuable and reliable tools for the investigation of solutions. Simulation techniques utilizing a quantum mechanical (QM) approach for the treatment of the chemically most relevant region so-called hybrid quantum mechanical/molecular mechanical (QM/MM) simulations have reached a level of accuracy that often equals or may even surpass experimental methods. The latter is true in particular whenever ultrafast (i.e., picosecond) dynamics prevail, such as in labile hydrates or structure-breaking systems. The recent development of an improved QM/MM framework, the quantum mechanical charge field (QMCF) ansatz, enables a broad spectrum of solute systems to be elucidated. As this novel methodology does not require any solute solvent potential functions, the applicability of the QMCF method is straightforward and universal. This advantage is bought, however, at the price of a substantial increase of the QM subregion, and an attendant increase in computational periods to levels of months, and even a year, despite parallelizing high-performance computing (HPC) clusters. Molecular dynamics (MD) simulations of chemical systems showing increasing complexity have been performed, and demonstrate the superiority of the QMCF ansatz over conventional QM/MM schemes. The systems studied include Pd2+, Pt2+, and Hg22+, as well as composite anions such as PO43- and ClO4-.

The Penetrating Power of β-Decay Recoils of Epithermal Energies in Organic Matter

1971 ◽  
Vol 49 (22) ◽  
pp. 3692-3699 ◽  
Author(s):  
N. H. Shafrir
Keyword(s):  
Gas Phase ◽  
Double Layer ◽  
Electrical Double Layer ◽  
Adsorption Layer ◽  
Unit Area ◽  
Initial Energy ◽  
Recoil Energy ◽  
Β Decay ◽  
Counter Ions ◽  
Surface Active

A method for the measurement of the extent of dislocation of the β-decaying nucleus from its equilibrium position is described. An ionized layer formed at the surface of an aqueous solution of an ionic surface-active substance served as a source of β-disintegrating atoms. The primary adsorbed surface-active ions give rise to an electrical double layer within the liquid phase. When the solution contains β-active ions, some will join the electrical double layer near the surface as counter ions. It was found that radioactive β-recoils arising in an adsorbed surface layer are able to leave the surface, collected on a negatively charged plate, and counted. In order to reach the gas phase, the β-recoils have to penetrate the primary organic adsorption layer. When the expanded adsorption layer is gradually compressed, particles of lower energy are stopped, resulting in decreased recoil activity. Extrapolation to zero β-recoil activity gives an approximate value for the mass per unit area of organic material which stops completely atoms of certain initial energy. For particle energies between 2 to 22 eV, a linear dependence is found between the maximum β-recoil energy and the "penetrating power". The corresponding organic stopping layers for this energy region are between 1.0 to about 1.6 × 10−7 g/cm2.

scholarly journals Investigation of the Causes of Violations of the Radioactive Balance between Radionuclides of the Uranium Decay Chain

2021 ◽  
Vol 8 (7) ◽  
pp. 95
Author(s):  
Soliyev T.I. ◽  
Muzafarov A.M.
Keyword(s):  
Daughter Nucleus ◽  
Theoretical Calculations ◽  
Technological Factor ◽  
Critical Factor ◽  
Decay Chain ◽  
Recoil Energy ◽  
Physical Factors ◽  
Underground Leaching ◽  
Radioactive Equilibrium ◽  
Nuclear Masses

Throughout the literature, it is mentioned that 15 radionuclides in the uranium decay chain have a constant radioactive equilibrium. Theoretical calculations give the value of the activity of each radionuclide in the uranium decay chain.This article examines various factors that affect the coefficient of radioactive equilibrium between radionuclides in the uranium decay chainThe concept of the coefficient of violations of nuclear equilibrium between radionuclides is adopted to determine the degree of violations in the uranium decay chain.Many nuclear-physical factors influence the radioactive balance between radionuclides. The most important of them is the recoil energy that the daughter nucleus receives when splitting from the mother nucleus.Another critical factor in the violation of the radioactive balance between radionuclides is the technological factor: leaching (acid, mini-reagent, bicarbonate, etc.) when leaching uranium by underground leaching of uranium.In addition, as a theoretical result of the study, the article presents a graphical relationship between the number of nuclear masses and the recoil energy of radionuclides in the uranium decay chain.

scholarly journals Explore the Chemical Space of Linear Alkanes Pyrolysis via Deep Potential Generator

2020 ◽  
Author(s):  
Jinzhe Zeng ◽  
Linfeng Zhang ◽  
Han Wang ◽  
Tong Zhu
Keyword(s):  
Ab Initio ◽  
Large Scale ◽  
Md Simulation ◽  
Learning Algorithm ◽  
Chemical Space ◽  
Md Simulations ◽  
Training Dataset ◽  
Complex Chemical ◽  
Pyrolysis Mechanism ◽  
Chemical Systems

<div> <div> <div> <p>Reactive molecular dynamics (MD) simulation is a powerful tool to study the reaction mechanism of complex chemical systems. Central to the method is the potential energy surface (PES) that can describe the breaking and formation of chemical bonds. The development of PES of both accurate and efficent has attracted significant effort in the past two decades. Recently developed Deep Potential (DP) model has the promise to bring ab initio accuracy to large-scale reactive MD simulations. However, for complex chemical reaction processes like pyrolysis, it remains challenging to generate reliable DP models with an optimal training dataset. In this work, a dataset construction scheme for such a purpose was established. The employment of a concurrent learning algorithm allows us to maximize the exploration of the chemical space while minimize the redundancy of the dataset. This greatly reduces the cost of computational resources required by ab initio calculations. Based on this method, we constructed a dataset for the pyrolysis of n-dodecane, which contains 35,496 structures. The reactive MD simulation with the DP model trained based on this dataset revealed the pyrolysis mechanism of n-dodecane in detail, and the simulation results are in good agreement with the experimental measurements. In addition, this dataset shows excellent transferability to different long-chain alkanes. These results demonstrate the advantages of the proposed method for constructing training datasets for similar systems. </p> </div> </div> </div>

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