186 research outputs found
Studies of concentration and temperature dependencies of precipitation kinetics in iron-copper alloys using kinetic monte carlo and stochastic statistical simulations
The earlier-developed ab initio model and the kinetic Monte Carlo method
(KMCM) are used to simulate precipitation in a number of iron-copper alloys
with different copper concentrations x and temperatures T. The same simulations
are also made using the improved version of the earlier-suggested stochastic
statistical method (SSM). The results obtained enable us to make a number of
general conclusions about the dependencies of the decomposition kinetics in
Fe-Cu alloys on x and T. We also show that the SSM describes the precipitation
kinetics in a fair agreement with the KMCM, and employing the SSM in
conjunction with the KMCM enables us to extend the KMC simulations to the
longer evolution times. The results of simulations seem to agree with available
experimental data for Fe-Cu alloys within statistical errors of simulations and
the scatter of experimental results. Comparison of results of simulations to
experiments for some multicomponent Fe-Cu-based alloys enables us to make
certain conclusions about the influence of alloying elements in these alloys on
the precipitation kinetics at different stages of evolution.Comment: 18 pages, 17 postscript figures, LaTe
Testing neutrino magnetic moment in ionization of atoms by neutrino impact
The atomic ionization processes induced by scattering of neutrinos play key
roles in the experimental searches for a neutrino magnetic moment. Current
experiments with reactor (anti)neutrinos employ germanium detectors having
energy threshold comparable to typical binding energies of atomic electrons,
which fact must be taken into account in the interpretation of the data. Our
theoretical analysis shows that the so-called stepping approximation to the
neutrino-impact ionization is well applicable for the lowest bound Coulomb
states, and it becomes exact in the semiclassical limit. Numerical evidence is
presented using the Thomas-Fermi model for the germanium atom.Comment: 5 pages, 1 figur
Transverse momentum spectra of charged particles in proton-proton collisions at GeV with ALICE at the LHC
The inclusive charged particle transverse momentum distribution is measured
in proton-proton collisions at GeV at the LHC using the ALICE
detector. The measurement is performed in the central pseudorapidity region
over the transverse momentum range GeV/.
The correlation between transverse momentum and particle multiplicity is also
studied. Results are presented for inelastic (INEL) and non-single-diffractive
(NSD) events. The average transverse momentum for is (stat.) (syst.) GeV/ and
\left_{\rm NSD}=0.489\pm0.001 (stat.) (syst.)
GeV/, respectively. The data exhibit a slightly larger than measurements in wider pseudorapidity intervals. The results are
compared to simulations with the Monte Carlo event generators PYTHIA and
PHOJET.Comment: 20 pages, 8 figures, 2 tables, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/390
The kinetic cluster-field method and its application to studies of L12-type orderings in alloys
The earlier-described master equation approach to configurational kinetics of nonequilibrium alloys is applied to study L12-type orderings in FCC alloys. We describe the kinetic tetrahedron cluster-field method which generalizes a similar method used for equilibrium systems to the case of non-equilibrium alloys. The method developed is used to simulate A1 → L12 and A1 → A1 + L12 transformations after a quench of an alloy from the disordered A1 phase to the single-phase L12 state or the two-phase A1 + L12 state for a number of alloy models with both short-range and long-range interactions. Simulations of the A1 → L12 transition show a sharp dependence of the microstructural evolution on the type of interaction, and particularly on the interaction range. The simulations also reveal a number of peculiar features in both the transient microstructures and the transformation kinetics, many of them agreeing well with experimental observations. Microstructural evolution under A1 → A1 + L12 transition was found to be less sensitive to the type of the finite-range (‘chemical’) interaction, while in the presence of elastic interaction this evolution shows a number of specific features which were earlier discussed phenomenologically by Khachaturyan and co-workers and are illustrated by our simulations. We also consider the problem of the occurrence of a transient congruent ordering under A1 → A1+ L12 transformation and discuss the microstructural features of this stage
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