Close-circuit domain quadruplets in BaTiO3_3 nanorods embedded in SrTiO3_3 film

Cylindrical BaTiO3 nanorods embedded in (100)-oriented SrTiO3 epitaxial film in a brush-like configuration are investigated in the framework of the Ginzburg-Landau-Devonshire model. It is shown that strain compatibility at BaTiO3/SrTiO3 interfaces keeps BaTiO3 nanorods in the rhombohedral phase even at room temperature. Depolarization field at the BaTiO3/SrTiO3 interfaces is reduced by an emission of the 109-degree or 71-degree domain boundaries. In case of nanorods of about 10-80 nm diameter, the ferroelectric domains are found to form a quadruplet with a robust flux-closure arrangement of the in-plane components of the spontaneous polarization. The out-of-plane components of the polarization are either balanced or oriented up or down along the nanorod axis. Switching of the out-of-plane polarization with coercive field of about $5.10^6$ V/m occurs as a collapse of a 71-degree cylindrical domain boundary formed at the curved circumference surface of the nanorod. The remnant domain quadruplet configuration is chiral, with the $C_4$ macroscopic symmetry. More complex stable domain configurations with coexisting clockwise and anticlockwise quadruplets contain interesting arrangement of strongly curved 71-degree boundaries.Comment: Erratta - corrected error in Fig.

Domain walls of ferroelectric BaTiO3 within the Ginzburg-Landau-Devonshire phenomenological model

Mechanically compatible and electrically neutral domain walls in tetragonal, orthorhombic and rhombohedral ferroelectric phases of BaTiO3 are systematically investigated in the framework of the phenomenological Ginzburg-Landau-Devonshire (GLD) model with parameters of Ref. [Hlinka and Marton, Phys. Rev. 74, 104104 (2006)]. Polarization and strain profiles within domain walls are calculated numerically and within an approximation leading to the quasi-one-dimensional analytic solutions applied previously to the ferroelectric walls of the tetragonal phase [W. Cao and L.E. Cross, Phys. Rev. 44, 5 (1991)]. Domain wall thicknesses and energy densities are estimated for all mechanically compatible and electrically neutral domain wall species in the entire temperature range of ferroelectric phases. The model suggests that the lowest energy walls in the orthorhombic phase of BaTiO3 are the 90-degree and 60-degree walls. In the rhombohedral phase, the lowest energy walls are the 71-degree and 109-degree walls. All these ferroelastic walls have thickness below 1 nm except for the 90-degree wall in the tetragonal phase and the 60-degree S-wall in the orthorhombic phase, for which the larger thickness of the order of 5 nm was found. The antiparallel walls of the rhombohedral phase have largest energy and thus they are unlikely to occur. The calculation indicates that the lowest energy structure of the 109-degree wall and few other domain walls in the orthorhombic and rhombohedral phases resemble Bloch-like walls known from magnetism.Comment: 12 pages, 9 figure

Функція мови і «тиші» в прозових творах Кларісе Ліспектор (The function of language and «silence» in prose works of Clarice Lispector)

У статті розглядаються функції мови та «тиші» в прозі бразильської письменниці Кларісе Ліспектор. Ці два концепти є важливими елементами в контексті літератури постмодернізму, і в творах К. Ліспектор – зокрема, адже вони сприяють глибшому розкриттю персонажів, їх функції в рамках наративу твору. В статті наводяться приклади використання даних концептів та досліджується їх значення в аспекті впливу на дискурс творів письменниці. (In this article the authors study the functions of language and «silence» in the prose of a Brazilian writer Clarice Lispector. These two concepts are very important elements in the context of post-modern literature, and specifically – in the works of Clarice Lispector, because they facilitate the deeper characterization of the heroes, their function in scopes of the works’ narrative. There are certain examples of usage of these concepts along with the research of their meaning in the context of the influence on the writer’s works’ discourse. The abstract deals with elements of philosophy of existentialism in the prose works of Clarice Lispector and the verbal manifestation of these elements in her texts. The language practices and the elements of manifestation of silence mitigate the defining of the role of the heroes in scopes of their ontological role in the discourse of the writer’s work. The article also emphasizes the peculiar linguistic characteristics of the female characters which are dominant in the works of this Brazilian author.

Жанр «кіберпанк» в американській літературі: причини виникнення та мовно-стилістичні особливості (The cyberpunk genre in American literature: the reasons of appearing, its stylistic and linguistic peculiarities)

У статті подаються висновки дослідження з приводу визначення культурних обставин, за яких сформувався літературний жанр «кіберпанк», який є явищем сучасної американської літератури. У нашому дослідженні ми розглядаємо лінгвістичні основи жанру, історичні обставини його існування. Однією з головних цілей, які ми маємо на меті досягти в ході нашої роботі є виявлення головних лексикологічних і стилістичних особливостей текстів жанру «кіберпанк». Ми також маємо на меті визначити основні загальні особливості текстів, які відносяться до цього жанру, а також визначити його основні тематики. (The article gives the observation of the cultural circumstances under which such literal genre as cyberpunk was invented which is the creation of American literal tradition. The analysis of the genre was performed from several points of view with applying of various methods i.e. onthological analysis, morphological analysis and stylistic analysis. In our work we thoroughly investigate the cultural and literature predecessors of this genre and how it is fitted in the system of science fiction genres. Special attention has been paid to distinguishing the main topics of such texts which differentiate them from the other texts of scientific literature. We have also tried to reflect the way these texts possess strong connection to the achievements of scientific-technological revolution, especially in the sphere of computing technology. In our research we observe the linguistic basis of the genre. One of the main goals that we pursue in our work is the distinguishing of the main lexicological and stylistic features of the cyberpunk texts – the peculiarities of metaphors’ creation, the specific features of IT neologisms creation (the usage of specific prefixes and suffixes). We also have paid certain attention to the way cyberpunk texts have influenced the modern literature process, especially the authors who have worked in the sphere of so-called counter-culture.

LiBC by polarized Raman spectroscopy: Evidence for lower crystal symmetry ?

The paper presents polarized Raman scattering study on a few-micron-size crystallite of LiBC with natural faces. The experiment on as grown sample has revealed a four lattice modes with frequencies at 1276 cm^-1, 830 cm^-1, 546 cm^-1 and 170 cm^-1, respectively. The number of observed Raman lines and their selection rules are incompatible with the assumed D6h symmetry. The modes at 1276 cm^-1 and 170 cm^-1 correspond to the expected Raman active modes. In contrast with the superconducting compound MgB2, the B-C bond stretching mode (at 1276 cm^-1) has rather small damping. The two "forbidden" modes (at 830 cm^-1 and 546 cm^-1) disappeared after subsequent thermal treatment.Comment: 4 pages, LaTeX, complementary experimental resul

Crossover between a displacive and an order-disorder phase transition

The phase transition in a three-dimensional array of classical anharmonic oscillators with harmonic nearest-neighbor coupling (discrete φ 4 model) is studied by Monte Carlo (MC) simulations and by analytical methods. The model allows us to choose a single dimensionless parameter a determining completely the behavior of the system. Changing a from 0 to + ∞ allows to go continuously from the displacive to the order-disorder limit. We calculate the transition temperature T c and the temperature dependence of the order parameter down to T = 0 for a wide range of the parameter a. The T c from MC calculations shows an excellent agreement with the known asymptotic values for small and large a. The obtained MC results are further compared with predictions of the mean-field and independent-mode approximations as well as with predictions of our own approximation scheme. In this approximation, we introduce an auxiliary system, which yields approximately the same temperature behavior of the order parameter, but allows the decoupling of the phonon modes. Our approximation gives the value of T c within an error of 5% and satisfactorily describes the temperature dependence of the order parameter for all values of a