The role of the adsortption layer in the formation of phase inhomogeneity at the InP/GaAs interface

The composition of the adsorption layer formed on the GaAs (001) surface at the initial stages of heteroepitaxial growth of InP in a chloride vapor-transport system is calculated within a thermodynamic approach. The obtained results allow us to understand the reasons for formation of a thin GaInAsP layer of variable composition experimentally observed at the InP/GaAs interface. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp.15–21, June, 2006.     

Influence of the inclusion shape on the conductivity of two-dimensional models of composites

The conductivity of some two-dimensional models of composites with randomly located and oriented dielectric inclusions of various shapes is considered. Exact analytical expressions are obtained for the effective conductivity σ _e at low concentration N of inclusions. The results are compared with the results of the corresponding computer experiment.     

The influence of a minor sodium addition on the contact melting of cadmium with bismuth,indium, and tin

The contact melting (CM) of Cd + 0.046 at % Na solid solution with indium, bismuth, and tin is studied. The dependence of the contact layer lengths on the duration of Cd + 0.046 at % Na CM with indium with electric current through is obtained. Addition of sodium is found to drastically affect the temperature of contact melting onset in (Cd + 0.046 at % Na)-Me (Me: In, Sn, Bi) systems. An attempt to interpret the results obtained is made.     

Calculations of the thermophysical properties of low-temperature Pb plasma at low densities

The pressure, internal energy, and electronic transport coefficients of low-temperature Pb plasma were calculated at the temperatures 10–100 kK by means of an earlier developed model (E. M. Apfelbaum, Contrib. Plasma Phys. 2019 , 59, e201800148). The plasma composition and thermodynamics were obtained using a chemical approach. The electronic transport coefficients were calculated within the relaxation time approximation with the new accurate momentum transfer cross-section electron-atom. The results of the present calculations have been compared with the new measurement data, obtained at relatively low densities, reaching 0.125 of the value in solid state, which corresponds to the area, where the model can be applied correctly. The good agreement between the calculations and measurements was obtained for both the pressure and the electrical conductivity.     

Inversion of electron spins in CaO with the reversal of the magnetic field

We have obtained population inversion of a system of polarized (P=80%) electron spins in a solid during a very fast (dB _z dt=4·10⁵ T·s ^–1) reversal of the external magnetic field. The electrons were trapped at oxygen vacancies in CaO single crystals. This method, whch does not exploit any high frequency electromagnetic field, has been for the first time successfully used to achieve an inverted state of electron spins in a solid. The negative temperature of an electron spin ensembleT=–23 mK has been obtained.     

The excitonic and zero-field splittings of the first triplet state of toluquinone single crystals

The pure electronic S ₀ → T ₁ transition of toluquinone has been studied in absorption using single crystals at 6 K and polarized light. The theory of the Zeeman effect on the crystal exciton levels is developed and compared with the experimental results. High-field measurements show that the factor group splitting is 0·32 cm^-1 and that the orbital plus state lies at higher energy. The ordering and energy separation of the magnetic substates of the factor group levels is also obtained. The latter results are confirmed by low field measurements and the following molecular zero-field splitting parameters are obtained: Y = +0·12, X = -0·02 and Z = -0·09 cm^-1.     

Phase diagram of the Mott transition in a two-band Hubbard model in infinite dimensions

The Mott metal-insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized dynamical mean-field theory recently developed by Bulla and Potthoff. The phase boundary of the metal-insulator transition is obtained analytically as a function of the on-site Coulomb interaction at the d-orbital, the charge-transfer energy between the d- and p-orbitals and the hopping integrals between p-d, d-d and p-p orbitals. The result is in good agreement with the numerical results obtained from the exact diagonalization method. Received 5 October 2000 and Received in final form 8 December 2000     

Measurement of the vector and tensor analyzing powers in dp elastic scattering at the energy of 880 MeV

The preliminary results on the angular distributions of the vector A _y and tensor A _yy , A _xx analyzing powers in dp elastic scattering at T _d = 880MeV are presented. A region of center-of-mass system angles from 60° to 140° is covered. The experimental data are compared with the preliminary calculations obtained within framework of different theoretical approaches. The experiment has been performed at the Internal Target Station at Nuclotron within the framework of the program on the study of light nuclei spin structure proposed at JINR (Russia) and RIBF (Japan).     

Measurement of the tensor analyzing power Ayy in the inelastic scattering of deuterons in the vicinity of excitation of baryonic resonances

The tensor A_yy and vector A_y analyzing powers in the inelastic scattering of deuterons with a momentum of 4.5 GeV/c on beryllium at an angle of 80 mr in the vicinity of baryonic resonances excitation have been measured. The A_yy data being in good agreement with the previous results obtained at a zero angle demonstrate an approximate t scaling up to - 0.9 (GeV/c)². The results of the experiment are compared with the predictions of the multiple-scattering and -meson exchange models. Received: 20 April 2000 / Accepted: 29 May 2000     

Construction of the two-electron contribution to the Fock matrix by numerical integration

A novel method to numerically calculate the Fock matrix is presented. The Coulomb operator is re-expressed as an integral identity, which is discretized. The discretization of the auxiliary t dimension separates the x, y, and z dependencies transforming the two-electron Coulomb integrals of Gaussian-type orbitals (GTO) to a linear sum of products of two-dimensional integrals. The s-type integrals are calculated analytically and integrals of the higher angular-momentum functions are obtained using recursion formulae. The contributions to the two-body Coulomb integrals obtained for each discrete t value can be evaluated independently. The two-body Fock matrix elements can be integrated numerically, using common sets of quadrature points and weights. The aim is to calculate Fock matrices of enough accuracy for electronic structure calculations. Preliminary calculations indicate that it is possible to achieve an overall accuracy of at least 10^?12 E _h using the numerical approach.     

On the nature of the magnetic transition in a Mott insulator

Using a combination of exact enumeration and the dynamical mean-field theory (DMFT) we study the drastic change of the spectral properties, obtained in the half-filled two-dimensional Hubbard model at a transition from an antiferromagnetic to a paramagnetic Mott insulator, and compare it with the results obtained using the quantum Monte Carlo method. The coherent hole (electron) quasiparticle spin-polaron subbands are gradually smeared out when the AF order disappears, either for increasing Coulomb repulsion U at fixed temperature T, or for increasing T at fixed U. Within the DMFT we present numerical evidence (a continuous disappearence of the order parameter) suggesting that the above magnetic transition is second order both in two and in three dimensions.Received: 20 November 2004, Published online: 9 April 2004PACS: 71.30. + h Metal-insulator transitions and other electronic transitions - 71.10.Fd Lattice fermion models (Hubbard model, etc.) - 79.60.-i Photoemission and photoelectron spectraThis work is dedicated to Professor Ole Krogh Andersen on the occasion of his 60th birthday.     

Production of <Emphasis Type="Italic">b</Emphasis>-quark jets at the Tevatron Collider in the Regge limit of QCD

The production of b-quark jets is considered in the approach of quasi-multi-Regge kinematics. This approach is based on the hypothesis of the Reggeization of t-channel gluons and quarks at high energies. Experimental data obtained by the CDF and D0 Collaborations at the Tevatron Collider for various spectra of b-quark jets are described quite accurately without invoking free parameters.     

Towards the assignment of the REMPI spectrum of Ph2O using CIS and TD-DFT methods

Tentative assignment of the low-lying vibrational features of the first electronic excited singlet-state S₁ of diphenyl ether (Ph₂O), obtained from resonance-enhanced multiphoton ionisation (REMPI) spectroscopy, is performed using CIS and time-dependent density functional theory (TD-DFT) methods. The potential energy surfaces, regarding the rotation of the phenyl rings relatively to the C–O–C plane, are obtained at the B3LYP/6-31G(d) level of theory, for the ground-state of neutral and cationic Ph₂O and for its first excited singlet state. The torsional barriers of the ground state of diphenyl ether were studied by means of quantum-chemical perturbations of increasing accuracy and an extrapolation to the complete basis set limit and full configuration interaction (FCI) was performed through the use of correlation consistent basis sets and the continued fraction method. The first adiabatic ionisation energy (AIE) of the twist conformer is computed at 8.60 eV in the FCI limit, much higher than the experimental results of Terlouw et al. (8.09±0.03 eV) and Paiva et al. (7.8±0.1 eV). The B3LYP result of 7.82 eV is, however, in reasonable agreement with the result of Paiva et al. The first singlet excitation energy for the twist conformation is found to be 5.5 eV at the CIS/6-311++G(d,p) level of theory. Some features of the experimental REMPI spectrum, previously obtained by one of the authors, are explained and a new insight on the ionisation energy of diphenyl ether is presented.     

Recent results from the Relativistic Heavy Ion Collider (RHIC)

The most recent physics results obtained at the Relativistic Heavy Ion Collider (RHIC) are surveyed. The survey is devoted to considering p + p, Cu + Cu, and Au + Au systems of colliding nuclei at c.m. energies of √ ^s NN = 200, 62.4, and 22.4 GeV. The results obtained within the first years of collider operation are discussed. New data on the production of high-transverse-momentum particles are presented. Manifestations of collective flows, such as the radial and elliptic flows, as well as the formation of a shock wave and a ridge, are considered. The results concerning heavy-quark production are also discussed.     

Monotonicity of the free energy in the stochastic Heisenberg model

The specific free energy of the state at timet of the stochastic Heisenberg model is shown to be non-increasing witht, and to strictly decrease whenever this state is not a Gibbs state of the Hamiltonian. The initial state is assumed to be translation invariant and suitably smooth. For such states a convergence theorem is obtained.This paper represents the second part of the author's thesis. The first part appeared as [5]     

One-dimensional non-nearest-neighbor random walks in the presence of traps

A one-dimensional lattice random walk in the presence ofm equally spaced traps is considered. The step length distribution is a symmetric exponential. An explicit analytic expression is obtained for the probability that the random walk will be trapped at thejth trapping site.     

Hints on integrability in the Wilsonian/holographic renormalization group

The Polchinski equations for the Wilsonian renormalization group in the D-dimensional matrix scalar field theory can be written at large N in a Hamiltonian form. The Hamiltonian defines evolution along one extra holographic dimension (energy scale) and can be found exactly for the subsector of Trϕ ⁿ (for all n) operators. We show that at low energies independently of the dimensionality D the Hamiltonian system in question reduces to the integrable effective theory. The obtained Hamiltonian system describes large wavelength KdV type (Burger-Hopf) equation with an external potential and is related to the effective theory obtained by Das and Jevicki for the matrix quantum mechanics.     

High temperature phase transitions in the crystal [4]of p-trimethylammoniumbenzenesulfonate zwitterion

Crystals of p-trimethylammoniumbenzenesulfonate (ZWT) have been obtained from the thermally induced soli d-state reaction of methyl p-dimethylaminobenzenesulfonate (MSE) or by recrystallization in aqueous solution. The characterization of four crystalline phases has been performed by calorimetric, birefringence, X-ray and Raman scattering studies. An unknown phase transition at room temperature yielding a new crystallographic phase has been found by calorimetric measurements. ZWT crystalline samples obtained from the solid state reaction are disordered as compared to ZWT single crystals obtained by growing from aqueous solution. This disorder is related to different arrangements of the phenyl ring orientations. Received 21 October 1998 and Received in final form 14 April 1999     

Functions of the nucleon structure and determination of the strong coupling constant

The properties of deep inelastic scattering at high energies, as well as results of fitting of experimental data on structure functions, obtained by BCDMS, SLAC, NMC, and BFP collaborations in fixed target experiments, with the aim of determining the strong coupling constant, the shape of parton distributions, and power corrections to F ₂(x, Q ²), are presented.     

Properties of metastable ising models evolving under the Swendsen-Wang dynamics

The behavior of the metastable nearest neighbor Ising model governed by Swendsen-Wang dynamics (SW) is investigated ind=2. The results are compared to those obtained in standard Metropolis dynamics. Both the SW and Metropolis systems are observed to decay from the metastable state via the formation of nucleating droplets. Nucleation rates are measured and found to agree with those predicted by classical nucleation theory. The growth rates of the droplets are observed to differ between the two dynamics. In addition, the dynamic critical exponentz is measured in a mean-field (Curie-Weiss) metastable Ising model at the spinodal. It is found that for SW dynamics,z=2. Since this is the same value as that obtained in the Metropolis case, this result shows that SW does not change the dynamical universality class at the spinodal.