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SUMMARY:The governing quantitative characteristics of radiation-induced se
gregation in Fe-Cr-Ni alloy
DTSTART;VALUE=DATE-TIME:20211221T124000Z
DTEND;VALUE=DATE-TIME:20211221T130000Z
DTSTAMP;VALUE=DATE-TIME:20241004T100008Z
UID:indico-contribution-36-232@indico.bitp.kiev.ua
DESCRIPTION:Speakers: Roman Skorokhod (Institute of Applied Physics of Nat
ional Academy of Sciences of Ukraine\, Sumy\, Ukraine)\nA profound consequ
ence of irradiation (neutron\, proton\, electron and heavy ion) of metal a
lloys is the spatial redistribution of alloy components. As a result\, the
re are enrichment or depletion of the main\, solute and impurity component
s of the alloy near the defect sinks. This phenomenon is called radiation-
induced segregation (RIS) and leads to degradation of mechanical and physi
cochemical properties of materials.\n\nThe spatial and temporal evolution
of the concentrations of alloy components $C_{k} $ $\\left(k=\\mathrm{Fe}\
,\\\, \\mathrm{Cr}\,\\\, \\mathrm{Ni}\\right)$ and point defects (PD) (vac
ancies $C_{\\mathit{v}} $ and interstitials $C_{i} $) in the ternary conce
ntrated Fe-Cr-Ni alloys under irradiation is described by the system of fi
ve coupled nonlinear partial differential equations [1-3]:\n$\\begin{equat
ion} \n\\left\\{\\begin{array}{l} {\\frac{\\partial C_{k} }{\\partial t} =
-\\mathbf{\\nabla}\\mathbf{J}_{k} \,} \\\\ {\\frac{\\partial C_{\\mathit{v
}} }{\\partial t} =-\\mathbf{\\nabla}\\mathbf{J}_{v} +K_{0} -R_{iv} C_{\\m
athit{v}} C_{i} -k_{v}^{2} D_{v} \\left(C_{v} -C_{v}^{eq} \\right)\,} \\\\
{\\frac{\\partial C_{i} }{\\partial t} =-\\mathbf{\\nabla }\\mathbf{J}_{i
} +K_{0} -R_{iv} C_{\\mathit{v}} C_{i} -k_{i}^{2} D_{i} \\left(C_{i} -C_{i
}^{eq} \\right).} \\end{array}\\right. \n\\end{equation}$\n \nwhere the f
luxes of atoms species $k$ is $\\mathbf{J}_k$\, vacancies $\\mathbf{J}_{\\
mathit{v}} $ and interstitial $\\mathbf{J}_{i} $ defined as:\n\n$\\begin{e
quation} \n\\mathbf{J}_{k} =-\\left(\\sum _{d=v\,i}d_{k\,d} C_{d} \\right
)\\mathbf{\\nabla}C_{k} +C_{k} \\left(d_{k\,v} \\mathbf{\\nabla }C_{v} -d_
{k\,i} \\mathbf{\\nabla }C_{i} \\right)\, \n\\end{equation}$ \n$\\begin{eq
uation} \n\\mathbf{J}_{v} =-\\sum _{k=\\mathrm{Fe}\,\\\, \\mathrm{Cr}\,\\\
, \\mathrm{Ni}}d_{k\,v} C_{k} \\mathbf{\\nabla }C_{v} +\\alpha C_{v} \\le
ft(\\sum _{k=\\mathrm{Fe}\,\\\, \\mathrm{Cr}\,\\\, \\mathrm{Ni}}d_{k\,v} \
\mathbf{\\nabla}C_{k} \\right)\, \n\\end{equation}$ \n$\\begin{equation}
\n\\mathbf{J}_{i} =-\\sum _{k=\\mathrm{Fe}\,\\\, \\mathrm{Cr}\,\\\, \\math
rm{Ni}}d_{k\,i} C_{k} \\mathbf{\\nabla}C_{i} -\\alpha C_{i} \\left(\\sum
_{k=\\mathrm{Fe}\,\\\, \\mathrm{Cr}\,\\\, \\mathrm{Ni}}d_{k\,i} \\mathbf{\
\nabla }C_{k} \\right)\, \n\\end{equation}$ \n$K_{0} $ is the production
rate of radiation PD\, $R_{iv} $ is the recombination rate of PD\, $k_{v}^
{2} $ and $k_{i}^{2} $ are the sink strengths for vacancies and interstiti
als respectively\, $C_{v}^{eq} $ and $C_{i}^{eq} $ are the equilibrium vac
ancy and interstitial concentrations\, $D_{v} $ and $D_{i} $ are the diffu
sion coefficients of vacancies and interstitial\, $d_{k\,v} $ and $d_{k\,i
} $ are the diffusivity coefficients of vacancies and interstitial. The sy
stem with the corresponding initial and boundary conditions is solved nume
rically (a detailed solution algorithm is given in [2]). \nThe aim of the
present paper is to calculate the governing quantitative characteristics o
f RIS for Fe-20%Cr-8%Ni alloy under the irradiation. That are: concentrati
on profiles of atoms species $k$ $C_{k} \\left(x\\right)$ and PD $C_{v\\le
ft(i\\right)} \\left(x\\right)\\\, $\, surface concentration of atoms spec
ies $k$ $C_{k}^{Surf} $\, the value of surface enrichment (depletion) of a
toms species $k$ $\\Delta C_{k} $\, the full width of the concentration pr
ofile of atoms species $k$ at half maximum enrichment (depletion) $\\mathr
m{FWHM}_{k} $\, segregation area of atoms species $k$ $S_{k} $ and discrim
inant of RIS of atoms species $k$ in a steady state $\\mathit{{\\mathfrak
D}}_{k} $. For example\, production rate dependence of surface depletion\,
$\\mathrm{FWHM} $ and segregation area for Cr and Ni are shown in Fig. 1.
\n\n\nFig. 1. Production rate dependence of surface Cr depletion $\\Delta
C_{\\mathrm{Cr}} $ and Ni enrichment $\\Delta C_{\\mathrm{Ni}} $ (solid li
ne)\, $\\mathrm{FWHM}_{\\mathrm{Cr}} $ and $\\mathrm{FWHM}_{\\mathrm{Ni}}
$ (dashed line) and segregation area of Cr $S_{\\mathrm{Cr}} $ and Ni $S_{
\\mathrm{Ni}} $ (dash-dotted line). Calculations were performed at tempera
ture$T=400$~$\\mathrm{{}^\\circ}$C\, dose $D=10$~dpa (displacement per ato
m).\n\nThe Authors acknowledge the support by the target research program
of National Academy of Sciences of Ukraine “Nuclear and radiation techno
logies for the energy sector and social needs” for 2019-2023.\n\n[1]. Wa
s G.S. Fundamentals of Radiation Materials Science: Metals and Alloys (2nd
ed.). New York: Springer-Verlag\, 2017. 1002 p.\n[2]. Skorokhod R.V.\, Ko
ropov A.V. Modeling of Radiation-Induced Segregation in Fe–Cr–Ni Alloy
s. Physics of the Solid State. 2019. Vol. 61\, P. 2269–2276.\n[3]. Korop
ov O.V.\, Skorokhod R.V.\, in Proceedings of Ninth International Scientifi
c-Practical Conference “Mathematics in Modern Technical University”\,
Kyiv\, December\, 28–29\, 2020. Vinnytsia: Publisher FOP Kushnir Yu. V.\
, 2021. P. 80-89. (in Ukrainian)\n\nhttps://indico.bitp.kiev.ua/event/8/co
ntributions/232/
LOCATION:Online meeting
URL:https://indico.bitp.kiev.ua/event/8/contributions/232/
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SUMMARY:Entanglement measures of a frustrated spin-$1/2$ Heisenberg octahe
dral chain within the localized-magnon approach
DTSTART;VALUE=DATE-TIME:20211221T122000Z
DTEND;VALUE=DATE-TIME:20211221T124000Z
DTSTAMP;VALUE=DATE-TIME:20241004T100008Z
UID:indico-contribution-36-225@indico.bitp.kiev.ua
DESCRIPTION:Speakers: Olesia Krupnitska (Institute for Condensed Matter Ph
ysics\, NAS of Ukraine)\nWe consider the spin-1/2 antiferromagnetic Heisen
berg model on the frustrated octahedral chain in a presence of the extern
al magnetic field. In a previous study [1]\, it was shown that the localiz
ed-magnon theory [2] can be modified for simpler calculation of concurrenc
e [3]\, which may serve as a measure of the bipartite entanglement between
nearest-neighbor and next-nearest-neighbor spins on squares of the octahe
dral chain. The results presented in [1] confirmed a new paradigm of the l
ocalized-magnons concept concerned with a simple calculation of entangleme
nt measure. This study is devoted to further application of a modified loc
alized-magnon theory for finding other entanglement measures. To be specif
ic\, we will consider such measures of entanglement as entanglement of for
mation and negativity [4-5]. It could be\, thus\, concluded that the local
ized-magnon theory can be straightforwardly adapted in order to calculate
the respective entanglement measures for a wide class of flat-band quantum
Heisenberg antiferromagnets. \n\n[1] J. Strecka\, O. Krupnitska and J. Ri
chter\, EPL\, ${\\bf 132}$ 30004 (2020).\n[2] J. Schulenburg et al.\, Phys
. Rev. Lett. ${\\bf 88}$\, 167207 (2002).\n[3] L. Amico et al.\, Rev. Mod.
Phys. ${\\bf 80}$\, 517 (2008).\n[4] A. Peres\, Phys. Rev. Lett. ${\\bf 7
7}$\, 1413 (1996).\n[5] G. Vidal and R.F. Werner\, Phys. Rev. A $\\bf65$\,
032314 (2002).\n\nhttps://indico.bitp.kiev.ua/event/8/contributions/225/
LOCATION:Online meeting
URL:https://indico.bitp.kiev.ua/event/8/contributions/225/
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SUMMARY:The charge and the dipole moment of quantized vortex structures in
superfluid systems
DTSTART;VALUE=DATE-TIME:20211221T120000Z
DTEND;VALUE=DATE-TIME:20211221T122000Z
DTSTAMP;VALUE=DATE-TIME:20241004T100008Z
UID:indico-contribution-36-224@indico.bitp.kiev.ua
DESCRIPTION:Speakers: Aleksandr Konstantinov (B.Verkin Institute for Low T
emperature Physics and Engineering of the National Academy of Sciences of
Ukraine)\nThe problem of the electric fields created outside a superfluid
liquid when quantum vortices and vortex rings appear inside the system is
solved. It is shown that in the presence of a magnetic field a quantum vo
rtex line acquires a linear charge density. The value of the charge densit
y depends on the angle between the circulation vector and the magnetic fie
ld. It was found that a charge is associated with a rectilinear vortex fil
ament\, and a dipole moment is associated with a vortex ring. It was found
that the key role while observing of electric fields outside the system i
s played by the shape of the surface that bounds the superfluid system. It
was established that the polarization associated with the velocity field
of the vortex ring does not cause the appearance of an electric field outs
ide an infinite cylindrical capillary with a circular cross section in the
case when the capillary axis coincides with the ring axis. If the system
does not have such a high symmetry and the axis of the ring does not coinc
ide with the axis of the capillary\, the electric field outside the system
is nonzero. The considered vortex structures can be generated by flows an
d can be associated with the transition of the system to a quantum turbule
nt state. For a laminar counterflow state of a superfluid system in a cyli
ndrical circular capillary the electric potential outside the system is id
entically equal to zero [1\,2]. Therefore\, the predicted magneto-electric
properties of quantum vortex structures can serve as a basis for creating
a sensitive quantum turbulent state detector for superfluid systems.\n\n[
1] S. I. Shevchenko and A. M. Konstantinov\, JETP Letters\, 109\, 790 (201
9).\n[2] S. I. Shevchenko and A. M. Konstantinov\, Low Temp. Phys. 46\, 48
(2020).\n\nhttps://indico.bitp.kiev.ua/event/8/contributions/224/
LOCATION:Online meeting
URL:https://indico.bitp.kiev.ua/event/8/contributions/224/
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