The dynamic symmetry and plastic deformation of diamond lattice

An analysis of possible transformations of moments of force by a diamond lattice has been made. The conditions of resonance transformations of moments of force by this lattice have been found. The dynamics symmetry of the diamond lattice has been determined in terms of the Shubnikov group Fd3m'. Besides, it has been found that resonance librationally deformed configurations are oneperiodic and have cores 〈110〉 two times more deformed than the surrounding area. As a result of the action of resonance phonons of the librational mode it is possible to generate a new kind of defects-bidislocations with Burgers vector components+[110]/2 and −[110]/2. It has been shown that bidislocations can play an essential role in plastic deformation of a diamond lattice and other related lattices.     

On the interference absorption of X-rays in crystals with weak deformations

The problem of Borrmann absorption (anomalous absorption) of X-rays in weakly deformed crystals is considered on the basis of Takagi’s approach to the dynamical theory. Using wave function considerations, the attenuation of rays is represented by exp(−σl) where the attenuation factor σ includes a parameter of the lattice deformation field. The possibility of cases σ = 0 and even σ < 0 is discussed.     

Thermodynamics of two-parameter quantum group Bose and Fermi gases

The high and low temperature thermodynamical properties of the two-parameter deformed quantum group Bose and Fermi gases with SU _p/q (2) symmetry are studied. Starting with a SU _p/q (2)-invariant bosonic as well as fermionic Hamiltonian, several thermodynamical functions of the system such as the average number of particles, internal energy and equation of state are derived. The effects of two real independent deformation parameters p and q on the properties of the systems are discussed. Particular emphasis is given to a discussion of the Bose-Einstein condensation phenomenon for the two-parameter deformed quantum group Bose gas. The results are also compared with earlier undeformed and one-parameter deformed versions of Bose and Fermi gas models. Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005.     

Integrable geodesic motion on 3D curved spaces from non-standard quantum deformations

The link between 3D spaces with (in general non-constant) curvature and quantum deformations is presented. It is shown, how the non-standard deformation of a sl(2) Poisson coalgebra generates a family of integrable Hamiltonians, that represent geodesic motions on 3D manifolds with a non-constant curvature, that turns out to be a function of the deformation parameter z. A different Hamiltonian defined on the same deformed coalgebra is also shown to generate a maximally superintegrable geodesic motion on 3D Riemannian and (2+1)D relativistic spaces whose sectional curvatures are all constant and equal to z. This approach can be generalized to arbitrary dimension. Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005.     

Potential energy surfaces for<Emphasis Type="Italic">N</Emphasis> =<Emphasis Type="Italic">Z</Emphasis>,<Superscript>20</Superscript>Ne-<Superscript>112</Superscript>Ba nuclei

We have calculated the potential energy surfaces forN = Z,²⁰Ne-¹¹²Ba nuclei in an axially deformed relativistic mean field approach. A quadratic constraint scheme is applied to determine the complete energy surface for a wide range of the quadrupole deformation. The NL3, NL-RA1 and TM1 parameter sets are used. The phenomenon of (multiple) shape coextistence is studied and the calculated ground and excited state binding energies, quadrupole deformation parameters and root mean square (rms) charge radii are compared with the available experimental data and other theoretical predictions.     

Crystallographic analysis of the <Emphasis Type="Italic">B</Emphasis>2 → <Emphasis Type="Italic">B</Emphasis>19′ martensite transformation in titanium nickelide

A phenomenological theory of martensite transformation is used to determine (select) the mechanism of B2 → B19′ transformation. The most realistic mechanism corresponds to the minimum additional rotation of a martensite plate needed to maintain the invariance of the habit plane. Equal values of the macroscopic shear direction and extent, the habit plane, the deformation for the invariant lattice, and the general deformation of shape are obtained for four different deformations. However, the supplementary rotation for each option is different. The minimum angle of rotation is observed for deformation by a martensite transformation with {21-1}B2 plane shear in the 〈-11-1〉 direction.     

Convexity of internal energy of cubic crystal deformed to orthorhombic structure

A generalized set of strain variablesq _r ^N , has been defined to develop the expression for a generalized set of second order and third-order elastic moduliC _rs ^N andC _rst ^N for a cubic crystal deformed to orthorhombic structure. The HessainC _rs ^N δq_rδq_s andC _rst ^N δq_rδq_sδq_t (r=1, 2……6; summation convention) are calculated in the new variables and compared withG-strength andS-strength, for both positive and negative loading environment. The convexity of the internal energy relative to various choice of strain measure is examined considering up to third degree terms in the internal energy expression. The computational results forbcc iron is presented according to the new moduli. The stable ranges thus obtained for iron under hydrostatic compressive and tensile stresses is found to generate the classical stable range, green-stable range and stretch-stable range as the specific cases. However,bcc iron does not seem to follow any conventional stable ranges under hydrostatic compression, where the present generalized stable range is found satisfactory.     

Count fluctuation analysis in the triaxial strongly deformed potential well of 163Lu

High-spin properties of the triaxial strongly deformed potential well in ¹⁶³Lu at excitation energies above resolvable bands have been investigated. Gated E _γ-E _γ spectra display clear ridges with moments of inertia corresponding to those observed for the discrete strongly deformed bands. A fluctuation analysis of the ridges yields a number of two-step paths of ≈ 40 and ≈ 20, when gating on triaxial strongly or normally deformed bands, respectively. These results show that a potential well at large deformation coexists with the normally deformed well, and indicate a mixing between states in the two wells at higher excitation energy. Received: 4 January 2002 / Accepted: 6 May 2002     

Infinite nuclear matter model and a new mass formula for atomic nuclei

The ground-state energy of an atomic nucleus with asymmetryβ is considered to be equivalent to the energy of a perfect sphere made up of the infinite nuclear matter of the same asymmetry plus a residual energyη called the local energy,η represents the energy due to shell, deformation, diffuseness and exchange Coulomb effect etc. Using this picture and the generalized Hugenholtz- Van Hove theorem of many-body theory a new mass formula has been developed. Based on this, a mass table containing the mass excesses of 3481 nuclei in the range 18 ⩽A ⩽ 267 has been made. This mass formula is compared with other mass models.     

Algebraic approach to quantum field theory on a class of noncommutative curved spacetimes

In this article we study the quantization of a free real scalar field on a class of noncommutative manifolds, obtained via formal deformation quantization using triangular Drinfel’d twists. We construct deformed quadratic action functionals and compute the corresponding equation of motion operators. The Green’s operators and the fundamental solution of the deformed equation of motion are obtained in terms of formal power series. It is shown that, using the deformed fundamental solution, we can define deformed *-algebras of field observables, which in general depend on the spacetime deformation parameter. This dependence is absent in the special case of Killing deformations, which include in particular the Moyal-Weyl deformation of the Minkowski spacetime.     

Anomalies of internal friction in CsI single crystal at liquid helium temperatures caused by plastic deformation

Acoustic relaxation in undeformed and plastically deformed CsI single crystal has been studied using the composite oscillator technique at frequencies (1–7) × 10⁵ Hz in the temperature range 2–15 K. Plastic deformation leads to appearance of an internal friction peak localized in the temperature interval 4–5 K. It is shown that the peak shifts towards higher temperatures when increasing the vibration frequency and corresponds to a thermally activated relaxation process with very low values of the activation energyU ≈ 1.9×10⁻³ eV and the attack frequencyν ₀≈6.7 × 10³ s⁻¹. Interaction of sound with dislocation kinks migrating in the second order Peierls relief is considered as a possible mechanism of the peak. Research was made possible in part by Grants U9T000 and U9T200 from the International Science Foundation and supported in part by the Fundamental Research Foundation of Ukraine (Project 2.4/156 “Bion”).     

Microstructure of Mo – 47% Re – 0.4% Zr alloys after rolling at room temperature. I. Anisotropy of microband structure and peculiarities of internal structure of microbands

The results of an electron microscopy investigation of microstructure of a Mo – 47% Re – 0.4% Zr alloy after rolling deformation (ε ≈ 90%) at room temperature are presented. A special focus is made on investigation of anisotropy of microband nanostructured states and high-energy defect substructures with high values of the crystal lattice curvature, dislocation density and local internal stresses. A disclination mechanism of reorientation as a mechanism of fragmentation of the internal microband structure is proposed.     

Frozen Rigging Model of the Energy Dominated Universe

Composite rigging systems, involving membranes that meet on strings that meet on monopoles, arise naturally by the Kibble mechanism as topological defects in field theories involving spontaneous symmetry breaking. Such systems will tend to freeze out into static lattice type configurations with energy contribution ultimately be provided by the membranes. It has been suggested by Bucher and Spergel that on scales large compared with the relevant (interstellar separation) distance characterizing the relevant mesh length, such a system may behave as a rigidity-stabilized solid, having an approximately isotropic stress energy tensor with negative pressure, as given by a polytropic index γ = w+1 = 1/3. It has recently been shown that such a system can be rigid enough to be stable if the number of membranes meeting at a junction is even (though not if it is odd). Using as examples an approximaely O(3) symmetric scalar field model that can provide an “8-color” (body-centered) cubic lattice, and an approximate U(1)× U(1) model offering a disordered “5-color” lattice, it is argued that such a mechanism can account naturally for the observed dark energy dominance of the universe, without ad hoc assumptions, other than that the relevant symmetry breaking phase transition should have occurred somewhere about the Kev energy range.     

Suppression of the scattering of conduction electrons by lattice phonons in palladium in the presence of small hydrogen (deuterium) inclusions

An increase has been found in the electrical conductivity of electrochemically dehydrogenated palladium hydrides (deuterides) as compared with original samples of pure palladium in a wide temperature range (75–300 K). It is shown that this effect is due to the suppression of the scattering of conduction electrons by phonons in the palladium lattice for T⩾θ (θ is the Debye temperature) in the presence of clusters of quasimetallic hydrogen (deuterium). Fiz. Tverd. Tela (St. Petersburg) 39, 2113–2117 (December 1997)     

Large area expansion of a soft dielectric membrane triggered by a liquid gaseous phase change

Soft dielectric membranes are easily deformed by external stimuli. Large area expansions are known in dielectric elastomer actuators, where the deformation is triggered by an applied electric field. Here we show large deformations of a soft elastomer membrane using the phase transition of an encapsulated liquid from the liquid to the gaseous state. The voltage required for actuating the soft membrane is only 10 V, as compared to 1000 V typically used in dielectric elastomer actuators. We report an area expansion of 120%, with large blocking forces from 1 to 6 N for 9 mm wide and 80 μm thick membranes. The proposed actuator concept is prone to miniaturization.     

The phenomenon of nucleon emission at high angular momentum states of fused compound systems

Nucleon emission from high spin fused compound systems is analyzed in the framework of the statistical theory of hot rotating (STHR) nuclei. This is an elaborate version of our earlier work and we present our results for¹⁵⁶Er,¹⁶⁶Er,¹⁶⁸ Yb and¹⁸⁸Hg. We predict an increase in neutron emission for¹⁶⁶Er due to the abrupt decrease in neutron separation energy aroundI ≈55ℏ. Since the drop in the separation energy is closely associated with the structural changes in the rotating nuclei, relative increase in neutron emission probability around certain values of angular momentum may be construed as evidence for the shape transition. A similar effect is predicted for¹⁶⁸Yb aroundI ≈55ℏ. We also extend the microscopic cranked Nilsson method (CNM) to hot nuclear systems and compare the results with that of the STHR method. The two methods yield different results for triaxially deformed nuclei although for biaxial deformations the results are identical. This is illustrated for¹⁸⁶Hg.     

Electronic properties of multinary alloys

Summary A model version of the coherent-potential approximation (CPA) is outlined to evaluate the fundamental energy gapsΓ _15v -Γ _1c ′,Γ _15v -L _1c ,Γ _15v -X _1c of a multinary solid solution. A comparison of theoretical results with the transition energy values obtained from direct interpolation of the corresponding values of ternary alloys is presented for some composition of the solution Al_1−x−y Ga _x In _y As at fixed lattice constants (matching the lattice constants of InP and AlAs). Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

The spin-one Ising model in the mean-spherical approximation

The spin-one Ising ferromagnet on a simple cubic lattice is treated in the mean-spherical approximation (MSA) for an exchange potentialJ(r) parametrized by a Kac-Baker inverse-range parameter γ. The mean-field result is recovered when γ→ 0; in this limit the result is exact. For γ≠ 0, a detailed analysis is given of the phase separation associated with the tricritical point that occurs. The analysis is made through the relation that gives the internal energy viaJ(r). It shows that the MSA result satisfactorily captures the important thermodynamic features of the tricritical point as long as γ is not too large. The case of CoulombicJ(r) is also considered; hereJ(r) is antiferromagnetic. An argument is given in support of the expectation that on the simple cubic and body-centered cubic lattices the CoulombicJ(r) will give rise to a tricritical point at which a λ-line of Néel points meets a paramagnetic-antiferromagnetic coexistence boundary.