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Lorenzo Malerba - One of the best experts on this subject based on the ideXlab platform.
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Ternary Fe-Cu-Ni Many-Body Potential to model reactor pressure vessel steels: First validation by simulated thermal annealing
Philosophical Magazine, 2009Co-Authors: Giovanni Bonny, Nicolas Castin, Roberto C Pasianot, Lorenzo MalerbaAbstract:In recent years the development of atomistic models dealing with microstructure evolution and subsequent mechanical property change in reactor pressure vessel steels, has been recognised as an important complement to experiments. In this framework, a literature study has shown the necessity of Many-Body interatomic Potentials for multi-component alloys. In this paper we develop a ternary Many-Body Fe-Cu-Ni Potential for this purpose. As a first validation, we used it to perform a simulated thermal annealing study of the Fe-Cu and Fe-Cu-Ni alloys. Good qualitative agreement with experiments is found, although fully quantitative comparison proved impossible, due to limitations in the used simulation techniques. These limitations are also briefly discussed here.
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Fe?Ni Many-Body Potential for metallurgical applications
Modelling and Simulation in Materials Science and Engineering, 2009Co-Authors: Giovanni Bonny, R.c. Pasianot, Lorenzo MalerbaAbstract:A Many-Body interatomic Potential for the Fe–Ni system is fitted, capable of describing both the ferritic and austenitic phase. The Fe–Ni system exhibits two stable ordered intermetallic phases, namely, L10 FeNi and L12 FeNi3, that are key issues to be tackled when creating a Fe–Ni Potential consistent with thermodynamics. A procedure, based on a rigid lattice Ising model and the theory of correlation functions space, is developed to address all the intermetallics that are possible ground states of the system. While controlling the ground states of the system, the mixing enthalpy and defect properties were fitted. Both bcc and fcc defect properties are compared with density functional theory calculations and other Potentials found in the literature. Finally, the Potential is thermodynamically validated by constructing the alloy phase diagram. It is shown that the experimental phase diagram is reproduced reasonably well and that our Potential gives a globally improved description of the Fe–Ni system in the whole concentration range with respect to the Potentials found in the literature.
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Iron-Copper-Nickel Many-Body Potential Consistent With Thermodynamics
Volume 1: Plant Operations Maintenance Engineering Modifications and Life Cycle; Component Reliability and Materials Issues; Next Generation Systems, 2009Co-Authors: Giovanni Bonny, R.c. Pasianot, N. Castin, Dmitry Terentyev, Lorenzo MalerbaAbstract:The Fe-Cu-Ni ternary alloy is of interest for nuclear applications because Cu and Ni are considered to have major effects on the embrittlement under irradiation of reactor pressure vessel steels. To improve our understanding on this phenomenon, large scale atomistic simulations in this model alloy are desirable. For this purpose we develop a ternary Fe-Cu-Ni Many-Body Potential consistent with thermodynamics is developed for the first time. The Potential was validated using molecular static and atomistic kinetic Monte Carlo simulations and a qualitative agreement with experiments was established. In particular, Cu precipitates were found to be enriched by Ni on the precipitate surface. Also, the effects diluting the Fe-Cu alloy by Ni on mean precipitate size and density showed similar trends as observed in experiments; i.e. no effect of Ni on the mean precipitate size and an increase in the maximum precipitate density due to the addition of Ni. In absolute terms, agreement with experiment is poor due to the limited box size used in the simulations, as correspondingly discussed.© 2009 ASME
Giovanni Bonny - One of the best experts on this subject based on the ideXlab platform.
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ternary fe cu ni many body Potential to model reactor pressure vessel steels first validation by simulated thermal annealing
Philosophical Magazine, 2009Co-Authors: Giovanni Bonny, R.c. Pasianot, Nicolas Castin, L MalerbaAbstract:In recent years, the development of atomistic models dealing with microstructure evolution and subsequent mechanical property change in reactor pressure vessel steels has been recognised as an important complement to experiments. In this framework, a literature study has shown the necessity of Many-Body interatomic Potentials for multi-component alloys. In this paper, we develop a ternary Many-Body Fe–Cu–Ni Potential for this purpose. As a first validation, we used it to perform a simulated thermal annealing study of the Fe–Cu and Fe–Cu–Ni alloys. Good qualitative agreement with experiments is found, although fully quantitative comparison proved impossible, due to limitations in the used simulation techniques. These limitations are also briefly discussed.
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Ternary Fe-Cu-Ni Many-Body Potential to model reactor pressure vessel steels: First validation by simulated thermal annealing
Philosophical Magazine, 2009Co-Authors: Giovanni Bonny, Nicolas Castin, Roberto C Pasianot, Lorenzo MalerbaAbstract:In recent years the development of atomistic models dealing with microstructure evolution and subsequent mechanical property change in reactor pressure vessel steels, has been recognised as an important complement to experiments. In this framework, a literature study has shown the necessity of Many-Body interatomic Potentials for multi-component alloys. In this paper we develop a ternary Many-Body Fe-Cu-Ni Potential for this purpose. As a first validation, we used it to perform a simulated thermal annealing study of the Fe-Cu and Fe-Cu-Ni alloys. Good qualitative agreement with experiments is found, although fully quantitative comparison proved impossible, due to limitations in the used simulation techniques. These limitations are also briefly discussed here.
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Fe?Ni Many-Body Potential for metallurgical applications
Modelling and Simulation in Materials Science and Engineering, 2009Co-Authors: Giovanni Bonny, R.c. Pasianot, Lorenzo MalerbaAbstract:A Many-Body interatomic Potential for the Fe–Ni system is fitted, capable of describing both the ferritic and austenitic phase. The Fe–Ni system exhibits two stable ordered intermetallic phases, namely, L10 FeNi and L12 FeNi3, that are key issues to be tackled when creating a Fe–Ni Potential consistent with thermodynamics. A procedure, based on a rigid lattice Ising model and the theory of correlation functions space, is developed to address all the intermetallics that are possible ground states of the system. While controlling the ground states of the system, the mixing enthalpy and defect properties were fitted. Both bcc and fcc defect properties are compared with density functional theory calculations and other Potentials found in the literature. Finally, the Potential is thermodynamically validated by constructing the alloy phase diagram. It is shown that the experimental phase diagram is reproduced reasonably well and that our Potential gives a globally improved description of the Fe–Ni system in the whole concentration range with respect to the Potentials found in the literature.
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Iron-Copper-Nickel Many-Body Potential Consistent With Thermodynamics
Volume 1: Plant Operations Maintenance Engineering Modifications and Life Cycle; Component Reliability and Materials Issues; Next Generation Systems, 2009Co-Authors: Giovanni Bonny, R.c. Pasianot, N. Castin, Dmitry Terentyev, Lorenzo MalerbaAbstract:The Fe-Cu-Ni ternary alloy is of interest for nuclear applications because Cu and Ni are considered to have major effects on the embrittlement under irradiation of reactor pressure vessel steels. To improve our understanding on this phenomenon, large scale atomistic simulations in this model alloy are desirable. For this purpose we develop a ternary Fe-Cu-Ni Many-Body Potential consistent with thermodynamics is developed for the first time. The Potential was validated using molecular static and atomistic kinetic Monte Carlo simulations and a qualitative agreement with experiments was established. In particular, Cu precipitates were found to be enriched by Ni on the precipitate surface. Also, the effects diluting the Fe-Cu alloy by Ni on mean precipitate size and density showed similar trends as observed in experiments; i.e. no effect of Ni on the mean precipitate size and an increase in the maximum precipitate density due to the addition of Ni. In absolute terms, agreement with experiment is poor due to the limited box size used in the simulations, as correspondingly discussed.© 2009 ASME
Francesco Paesani - One of the best experts on this subject based on the ideXlab platform.
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temperature dependent vibrational spectra and structure of liquid water from classical and quantum simulations with the mb pol Potential energy function
Journal of Chemical Physics, 2017Co-Authors: Sandeep K Reddy, Daniel R Moberg, Shelby C Straight, Francesco PaesaniAbstract:The structure of liquid water as a function of temperature is investigated through the modeling of infrared and Raman spectra along with structural order parameters calculated from classical and quantum molecular dynamics simulations with the MB-pol Many-Body Potential energy function. The magnitude of nuclear quantum effects is also monitored by comparing the vibrational spectra obtained from classical and centroid molecular dynamics, both in intensities and peak positions. The observed changes in spectral activities are shown to reflect changes in the underlying structure of the hydrogen-bond network and are found to be particularly sensitive to Many-Body effects in the representation of the electrostatic interactions. Overall, good agreement is found with the experimental spectra, which provides further evidence for the accuracy of MB-pol in predicting the properties of water.
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On the accuracy of the MB-pol Many-Body Potential for water: Interaction energies, vibrational frequencies, and classical thermodynamic and dynamical properties from clusters to liquid water and ice
The Journal of chemical physics, 2016Co-Authors: Sandeep K Reddy, Daniel R Moberg, Shelby C Straight, Pushp Bajaj, C. Huy Pham, Marc Riera, Miguel A. Morales, Chris Knight, Andreas W. Götz, Francesco PaesaniAbstract:The MB-pol Many-Body Potential has recently emerged as an accurate molecular model for water simulations from the gas to the condensed phase. In this study, the accuracy of MB-pol is systematically assessed across the three phases of water through extensive comparisons with experimental data and high-level ab initio calculations. Individual Many-Body contributions to the interaction energies as well as vibrational spectra of water clusters calculated with MB-pol are in excellent agreement with reference data obtained at the coupled cluster level. Several structural, thermodynamic, and dynamical properties of the liquid phase at atmospheric pressure are investigated through classical molecular dynamics simulations as a function of temperature. The structural properties of the liquid phase are in nearly quantitative agreement with X-ray diffraction data available over the temperature range from 268 to 368 K. The analysis of other thermodynamic and dynamical quantities emphasizes the importance of explicitly including nuclear quantum effects in the simulations, especially at low temperature, for a physically correct description of the properties of liquid water. Furthermore, both densities and lattice energies of several ice phases are also correctly reproduced by MB-pol. Following a recent study of DFT models for water, a score is assigned to each computed property, which demonstrates the high and, in many respects, unprecedented accuracy of MB-pol in representing all three phases of water.
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modeling molecular interactions in water from pairwise to many body Potential energy functions
Chemical Reviews, 2016Co-Authors: Gerardo Andres Cisneros, Kjartan Thor Wikfeldt, Lars Ojamae, Hedieh Torabifard, Albert P Bartok, Gabor Csanyi, Valeria Molinero, Francesco PaesaniAbstract:Almost 50 years have passed from the first computer simulations of water, and a large number of molecular models have been proposed since then to elucidate the unique behavior of water across different phases. In this article, we review the recent progress in the development of analytical Potential energy functions that aim at correctly representing Many-Body effects. Starting from the Many-Body expansion of the interaction energy, specific focus is on different classes of Potential energy functions built upon a hierarchy of approximations and on their ability to accurately reproduce reference data obtained from state-of-the-art electronic structure calculations and experimental measurements. We show that most recent Potential energy functions, which include explicit short-range representations of two-body and three-body effects along with a physically correct description of Many-Body effects at all distances, predict the properties of water from the gas to the condensed phase with unprecedented accuracy,...
Joel M. Bowman - One of the best experts on this subject based on the ideXlab platform.
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Communication: VSCF/VCI vibrational spectroscopy of H7O3+ and H9O4+ using high-level, Many-Body Potential energy surface and dipole moment surfaces.
The Journal of chemical physics, 2017Co-Authors: Joel M. BowmanAbstract:The vibrational spectra of protonated water clusters continue to be of great interest and a significant challenge to theory. We report high-level, coupled-mode anharmonic (VSCF/VCI) calculations of vibrational spectra of two protonated water clusters, H7 O 3 + and H9 O 4 + , using the Watson Hamiltonian and new full-dimensional, high-level Many-Body Potential energy and dipole moment surfaces. These Many-Body representations are first validated against direct CCSD(T)-F12b/aug-cc-pVTZ calculations of the double-harmonic spectra of these clusters. Then they are used with a 4-mode representation of the Potential and 18 coupled modes to obtain the anharmonic coupled-mode spectra of these clusters. The calculated spectra agree well with recent Ar-tagged action spectra. In the case of H9 O 4 + , a “side-by-side” comparison shows a very good agreement with virtually every experimental feature.
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A new Many-Body Potential energy surface for HCl clusters and its application to anharmonic spectroscopy and vibration-vibration energy transfer in the HCl trimer.
The journal of physical chemistry. A, 2014Co-Authors: John S. Mancini, Joel M. BowmanAbstract:The hydrogen bond has been studied by chemists for nearly a century. Interest in this ubiquitous bond has led to several prototypical systems emerging to studying its behavior. Hydrogen chloride clusters stand as one such example. We present here a new Many-Body Potential energy surface for (HCl)n constructed from one-, two-, and three-body interactions. The surface is constructed from previous highly accurate, semiempirical monomer and dimer surfaces, and a new high-level ab initio permutationally invariant full-dimensional three-body Potential. The new three-body Potential is based on fitting roughly 52,000 three-body energies computed using coupled cluster with single, doubles, perturbative triples, and explicit correlation and the augmented correlation consistent double-ζ basis set. The first application, described here, is to the ring HCl trimer, for which the Many-Body representation is exact. The new Potential describes all known stationary points of the trimer as well its dissociation to either three monomers or a monomer and a dimer. The anharmonic vibrational energies are computed for the three H-Cl stretches, using explicit three-mode coupling calculations and local-monomer calculations with Huckel-type coupling. Both methods produce frequencies within 5 cm(-1) of experiment. A wavepacket calculation based on the Huckel model and full-dimensional classical calculation are performed to study the monomer H-Cl stretch vibration-vibration transfer process in the ring HCl trimer. Somewhat surprisingly, the results of the quantum and classical calculations are virtually identical, both exhibiting coherent beating of the excitation between the three monomers. Finally, this representation of the Potential is used to study properties of larger clusters, namely to compute optimized geometries of the tetramer, pentamer, and hexamer and to perform explicit four-mode coupling calculations of the tetramer's anharmonic stretch frequencies. The optimized geometries are found to be in agreement with those of previous ab initio studies and the tetramer's anharmonic frequencies are computed within 11 cm(-1) of experiment.
Amand Faessler - One of the best experts on this subject based on the ideXlab platform.
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semiclassical expansion of quantum characteristics for many body Potential scattering problem
Annalen der Physik, 2007Co-Authors: M I Krivoruchenko, C Fuchs, Amand FaesslerAbstract:In quantum mechanics, systems can be described in phase space in terms of the Wigner function and the star-product operation. Quantum characteristics, which appear in the Heisenberg picture as the Weyl's symbols of operators of canonical coordinates and momenta, can be used to solve the evolution equations for symbols of other operators acting in the Hilbert space. To any fixed order in the Planck's constant, Many-Body Potential scattering problem simplifies to a statistical-mechanical problem of computing an ensemble of quantum characteristics and their derivatives with respect to the initial canonical coordinates and momenta. The reduction to a system of ordinary differential equations pertains rigorously at any fixed order in ħ. We present semiclassical expansion of quantum characteristics for Many-Body scattering problem and provide tools for calculation of average values of time-dependent physical observables and cross sections. The method of quantum characteristics admits the consistent incorporation of specific quantum effects, such as non-locality and coherence in propagation of particles, into the semiclassical transport models. We formulate the principle of stationary action for quantum Hamilton's equations and give quantum-mechanical extensions of the Liouville theorem on conservation of the phase-space volume and the Poincare theorem on conservation of 2p-forms. The lowest order quantum corrections to the Kepler periodic orbits are constructed. These corrections show the resonance behavior.
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semiclassical expansion of quantum characteristics for many body Potential scattering problem
arXiv: Nuclear Theory, 2006Co-Authors: M I Krivoruchenko, C Fuchs, Amand FaesslerAbstract:In quantum mechanics, systems can be described in phase space in terms of the Wigner function and the star-product operation. Quantum characteristics, which appear in the Heisenberg picture as the Weyl's symbols of operators of canonical coordinates and momenta, can be used to solve the evolution equations for symbols of other operators acting in the Hilbert space. To any fixed order in the Planck's constant, Many-Body Potential scattering problem simplifies to a statistical-mechanical problem of computing an ensemble of quantum characteristics and their derivatives with respect to the initial canonical coordinates and momenta. The reduction to a system of ordinary differential equations pertains rigorously at any fixed order in $\hbar$. We present semiclassical expansion of quantum characteristics for Many-Body scattering problem and provide tools for calculation of average values of time-dependent physical observables and cross sections. The method of quantum characteristics admits the consistent incorporation of specific quantum effects, such as non-locality and coherence in propagation of particles, into the semiclassical transport models. We formulate the principle of stationary action for quantum Hamilton's equations and give quantum-mechanical extensions of the Liouville theorem on the conservation of phase-space volume and the Poincar\'e theorem on the conservation of $2p$ forms. The lowest order quantum corrections to the Kepler periodic orbits are constructed. These corrections show the resonance behavior.