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1.
Atomistic simulations of segregation to (100) free surface in Ag–Au, Au–Pd, and Cu–Ni alloy systems have been performed for a wide range of temperatures and compositions within the solid solution region of these alloy phase diagrams. In addition to the surface segregation profiles, surface free energies, enthalpies, and entropies were determined. These simulations were performed within the framework of the free energy simulation method, in which an approximate free energy functional is minimized with respect to atomic coordinates and atomic site occupation. The effects of the relaxation with respect to either the atomic positions or the atomic concentrations are discussed. For all alloy bulk compositions (0.05 C 0.95) and temperatures (400 T(K) 1,100) examined, Ag, Au, and Cu segregates to the surface in the Ag–Au, Au–Pd, and Cu–Ni alloy systems, respectively. The present results are compared with several theories for segregation. The resultant segregation profiles in Au–Pd and Ag–Au alloys are shown to be in good agreement with an empirical segregation theory, while in Cu–Ni alloys the disagreement in Ni-rich alloys is substantial. The width of the segregation profile is limited to approximately three to four atomic planes. The surface thermodynamic properties depend sensitively on the magnitude of the surface segregation, and some of them are shown to vary linearly with the magnitude of the surface segregation. 相似文献
2.
S. M. Borodachev 《Russian Physics Journal》1979,22(4):373-377
Calculations are made of the residual resistance of the ordered binary alloys stemming from the difference between the d levels of the components. The residual resistance is found to be dependent on the degree of the long-range order. It is established that in alloys in which the Fermi energy EF is far from the d resonances decreases monotonically as increases. When EF approaches one of the resonance levels the resistance increases severalfold and varies monotonically with . The results are used in interpreting the anomalies of the temperature dependence of the resistance of iron-palladium alloys.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 39–44, April, 1979.The author is indebted to A. A. Kuranov and P. N. Syutkin for providing us with detailed experimental data, and to S. I. Masharov for his fruitful discussion. 相似文献
3.
Levinson's theorem for the one-dimensional Schrödinger equation with asymmetric potential which decays at infinity faster thanx
–2 is established by theSturm-Liouville theorem. The critical case where the Schrödinger equation hasa finite zero-energy solution is also analyzed. It is demonstrated that the numberof bound states with even (odd) parityn
+(n
–) is related to the phase shift + (0)[– (0)] of the scattering states with the same parity at zero momentum as + (0)+ /2 =n
+ and – (0) =n
– for the noncritical case, and + (0) =n
+ and– (0) – /2 =n
– for the critical case. 相似文献
4.
We propose a microscopic approach to the study of phase transitions in fluid mixtures. It is based on the collective variables method with a reference system. The problem of definition of the order parameter in a two-component fluid system is considered in detail. This system is described with two sets of collective variables:
k and k. It is shown that the CV connected with the order parameter is k=0 in the case of a gas–liquid critical point as well as in the case of a mixing–demixing phase transition. The relations between the microscopic parameters, temperature, density and concentration which determine the particular form of 0 for each of these phenomena are obtained. Based on these results we will be able to construct an effective Ginsburg–Landau–Wilson Hamiltonian. 相似文献
5.
The internal oxidation of dilute AgIn alloys in open air versus In concentration and oxidation temperature was investigated by the TDPAC technique. The111In interaction described by the broad quadrupole frequencies distribution aroundv
Q = 115 MHz and =0.5–0.7 was observed and interpreted as due to nonstoichiometric In–OX cluster formation. For higher temperatures and more concentrated alloys additionally quasiunique frequencyv
Q 157 MHz with 0.28 was evidenced and ascribed to111In interaction inside In2O3 precipitates. The internal oxidation under reduced oxygen pressures was studied and the thermal stability of the complex formed was tested. The effect of surface preparation on internal oxidation was observed. 相似文献
6.
Atomistic simulations of segregation to [001] 5 twist boundaries in Cu–Ni, Au–Pd, and Ag–Au alloy systems have been performed for a wide range of temperatures and compositions within the solid solution region of these alloy phase diagrams. In addition to the grain boundary segregation profiles, grain boundary free energies, enthalpies, and entropies were determined. These simulations were performed within the framework of the free energy simulation method, in which an approximate free energy functional is minimized with respect to atomic coordinates and atomic site occupation. For all alloy bulk compositions (0.05 C 0.95) and temperatures (400 T (K) 1,100) examined, Cu and Au segregates to the boundary in the Cu–Ni and Au–Pd alloy systems, respectively; although in the Ag–Au alloys, the majority element segregates to the boundary. The width of the segregation profile is limited to approximately three to four (002) atomic planes. The classical theories for the segregation, and the effects of the relaxation with respect to either the atomic positions or the atomic concentrations, are discussed. The boundary thermodynamic properties depend sensitively on the magnitude of the boundary segregation, and some of them are shown to vary linearly with the magnitude of the grain boundary segregation. 相似文献
7.
Measurements of fluorescence quantum yield D/oD of Na-fluorescein (donor; D) versus concentration of rhodamine B (acceptor; A) in viscous solutions have been carried out. The donor concentration in these solutions was as follows:C
D=2·10–2
M (system I), 1.5·10–2
M (II), 10–2
M (III), 3·10–3
M (IV), and 5·10–5
M (V). The experimental results have been compared with current theories of nonradiative electronic energy transfer (NEET). In the case of very strong migration (systems I, II, and III), a significant influence of correlations (between configurations of D and A molecules in the surroundings of successively excited donors) on quantum yield D/oD has been determined. Experimental values have been found to be clearly higher in comparison with those predicted theoretically. The influence of possible factors on the decrease in the effectiveness of excitation energy transport to traps-acceptors in systems of very strong migration has been discussed.Dedicated to Professor A. Kawski on the occasion of his 65th birthday. 相似文献
8.
Applying the model of the anharmonic oscillator, phenomenological expressions were derived, allowing calculation of the components of tensors describing non-linear magneto-electric susceptibilities. Detailed calculations were carried out for the pseudo-tensor of fourth order eeem in terms of which magneto-optical birefringence and rotation are expressed for the monocrystals KDP, DKDP, ADP, KDA, LiNbO3, LiTaO3 and NaClO3. From the results obtained it follows that non-linear magneto-electric susceptibilities, which are described by the pseudo-tensor eeem are of the order of 10–16 m V–1T–1.Part of this work was carried out under Research Project MR 15. 相似文献
9.
Pseudopotential theory is used to study the dependence of energy of vacancy formation EIV
f in binary replacement alloys as a function of the degree of far order is shown that E
IV
f
=Eo+E·]2, where Eo is the energy of vacancy formation in a disordered alloy, E then contains the ordering energy. It is shown with examples of the alloys CuZn, AuZn, and AgCd that the energy of vacancy formation can decrease with increase in the degree of far order. It is found that in calculating the vacancy formation energy it is necessary to consider lattice relaxation energy, since such consideration can lead to a change in the sign of E.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 62–67, June, 1984. 相似文献
10.
The Wilson expansion of the field operator productA
1(x
1)A
2(x
2) may be used to define composite operators which are local with respect to 1/2(x
1+x
2) and depend in addition on a vector proportional to the distancex
1–x
2. It is proved that the composite operators are polynomials in , for fixed 2 0, and that their dependence on 2 only involves powers of 2 and lg2.This work was supported in part by the National Science Foundation Grant No. GP-25609. 相似文献
11.
A. V. Zakharov 《Russian Physics Journal》1978,21(4):442-448
Long-wavelength gravitational perturbations are studied in an isotropic expanding universe filled with an ultrarelativistic gas. A kinetic study in the collisionless approximation shows that scalar and vector perturbations which appear at a time
0 1/n, where N is the wave vector and is the time coordinate x4, grow if the perturbation of the macroscopic momentum density of the gas at time
0 is nonvanishing. The growth continues until the time
1=270, at which the perturbation of the macroscopic momentum density of the gas vanishes. A solution is also derived for tensor perturbations in the limit n 1.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 37–45, April, 1978. 相似文献
12.
A numerical investigation has been carried out on the influence of the antireflection (AR) coating of laser, the coupling efficiency of laser and fiber (), and the reflectivity of fiber grating (R
g) on the side-mode suppression ratio (SMSR) of the fiber grating external cavity laser (FGECL). The FGECL was fabricated by the assembly of the multimode Fabry–Perot (FP) laser chip and fiber grating. The results showed that the FGECL with a lower AR coating, higher and R
g exhibited a better SMSR. A comparison of the SMSR dependence on the and R
g showed that SMSR increased more rapidly with increasing than SMSR for R
g. These spectral characteristic studies of the SMSR dependence on the device parameters of the AR coating, , and R
g may provide useful device designs for the practical fabrication of a FGECL for use in dense wavelength division multiplexing (DWDM) applications. 相似文献
13.
Conclusions Crystal phosphors with photon multiplication in the optical range can be used as efficient light transformers. Their use in mercury-free luminescent gas-discharge lamps is especially promising. Analysis of the present position as regards neon discharges indicates that by using phosphors with
t=2–3 it might be possible to create light sources with an efficiency of 30–50 1m/W which would operate solely under outdoor lighting conditions. Evaluation of the prospects of developing light transformers with
t=2–3 indicates that this problem is solvable in principle.We are grateful to the staff of the Ionic Crystal Physics Sector of the Institute of Physics and Astronomy, AS Estonian SSR, and especially to G. Liid'ya, R. Kink, N. Lushchik, I. Meriloo, N. Rooze, and R. Milenina for taking part in our discussions of the problem of transformers with photon multiplication. We also wish to thank V. V. Fedorov and F. A. Butaeva of the All-Union Scientific Institute of Lighting Engineering, who drew our attention to the importance of developing luminophors with>1 for new light sources.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 10, No. 1, pp. 127–133, January, 1969. 相似文献
14.
This paper constitutes a theoretical study of the influence of interstitial impurity atoms on the type of order-disorder transition in an alloy of the AB3-Cin type with an hcp structure. Allowance is made for a variety of types of interstices over the range 0 1. The free energy is calculated by the Gorskii-Bragg-Williams method. In the presence of an impurity there may be a change in the magnitude of the jump taking place in the degree of long-range order at the transition point, and also a change in the type of order-disorder transition occurring.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 20–26, March, 1974. 相似文献
15.
I. G. Aznauryan 《Zeitschrift fur Physik C Particles and Fields》1995,68(3):459-462
We show that photoproduction experiments provide propitious conditions to study the exotic state 1–+ in the and channels. For unpolarized photons contributions from natural and unnatural parity exchanges do not interfere with each other, a fact which permits to estimate the correctness of phase shift analyses. In photoproduction of the + system in the mass range ofa
2(1320) a more stringent limit on the product (1–+)Br(1–+) can be obtained than in experiments on Primakoff production on nuclei. Particularly favourable is the study of the state 1–+ in the coherent photoproduction of the 0 and 0 systems on nuclei, with significantly enlarged statistics and a simplified phase shift analysis. 相似文献
16.
The conditions for the existence of solutions ofD
µ=±cµ are discussed. In general, it is not sufficient to consider only the first integrability condition [D
µ,D
v
]=–2c
2{µv}; in particular, the second integrability condition is needed to explain why, in certain cases, only for one choice of sign does a solution exist. The Killing spinor-tensors, as defined by Walker and Penrose, are shown to be the spinorial equivalent of conformal Killing tensors. Their relationship to the Killing spinors and spinor-vectors used in supergravity, is given.On leave from the Institute for Theoretical Physics of the State University of New York at Stony BrookWork supported in part by the U.S. Department of Energy under Contract No. DEAC-03-81-ER 40050 and Weingart Fellowship 相似文献
17.
The width of S-wave quarkonium decays (c, b ; and J/, Y e+e–) are calculated using the quasipotential approach. The nontrivial dependence of decay amplitude on relative quark momentum is considered. It is shown that relativistic corrections reach values of 30–50% in the processes studied.Samara State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 46–53, May, 1995. 相似文献
18.
L. I. Tsaregorodtsev 《Russian Physics Journal》1991,34(2):136-140
A study is made of the production of an electron-positron pair and a photon from the vacuum in a Robertson-Walker space with metric ds2=a2()(d2–dx2–dy2–dx2). In Minkowski space, this process is forbidden by the conservation laws. The differential probability of the process is calculated, and its behavior in various kinematic regions is investigated. The probability of the process is estimated numerically for times close to the electron Compton time, and the probability of production of a pair and photon from the vacuum is compared with the probability of pair production in the absence of radiative coupling.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 61–66, February, 1991. 相似文献
19.
H. Metzner R. Sielemann S. Klaumünzer R. Butt W. Semmler 《Zeitschrift für Physik B Condensed Matter》1985,61(3):267-281
Radiation-induced lattice defects in high-purity niobium have been investigated in the temperature range of 30K to 540 K by means of - perturbed angular correlation (PAC) measurements using the radioactive probes100Pd/100Rh and111In/111Cd. Both probes were produced within the niobium samples by means of heavy-ion nuclear reactions. At the Pd impurities trapping of defects occurred during heavy-ion irradiation at about 30 K in two defined configurations: defect 1(Pd) withv
Q1=e
2
qQ/h=42(±2) MHz, 1=0 and defect 2 (Pd) withv
Q2=(±2) MHz, 2=1. Two defects were observed at the In impurities in annealing stage III (around 250 K) after heavy-ion as well as electron irradiations: defect 1(In) withv
Q1=87(±1) MHz, 1=0 and defect 2(In) withv
Q2=105(±2) MHz, 2=0.65(±0.02). A third defect (defect 3(In):v
Q3=177(±2) MHz, 30.2) appeared above 260 K after heavy-ion irradiation only. The data are interpreted in terms of interstitial trapping at the Pd impurities and vacancy trapping at the In impurities. Information on the microscopic structure of defect 1(In) and 2(In) is obtained from a PAC-single-crystal experiment. For defect 1(In) axial 111-symmetry is found, which leads us to identify this defect with a monovacancy as nearest neighbor with respect to the In probe. Defect 2(In) is the trapped divacancy for which an orientation is found that is consistent with both vacancies being nearest neighbor to the probe but second nearest neighbors to each other. 相似文献
20.
K. -H. König H. Jung O. Schärpf H. Brömer 《Zeitschrift für Physik B Condensed Matter》1989,76(4):493-499
57Fe NMR measurements with a Néel-type single crystal are described. The behaviour of the magnetic structure was calculated as function of the internal fieldH
i. A clear distinction between wall and domain signals could be made. The corresponding relative enhancement factors
w
r
(H
i) and
D
r
(H
i) have been calculated and are in agreement with the measurements. The relaxation in the 90° Bloch walls is pure exponential. Both ratesT
1
–1 andT
2
–1 are proportional to
w
2
(H
i). The measurements make proof, that the 90° walls are folded inside the crystal.K.-H. König and H. Brömer, Verhandl. DPG(VI)22, I, AM-14.11 (1987) 相似文献