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## Publications

Publications (103)

A gradual construction of signal based on the Weierstraß-Mandelbrot function starting from a single pure tone up to a fully developed self-similar waveform allows one to aurally perceive gain/loss of self-similarity symmetry. A numerically synthesized example involves a scaling transformation with the value of scaling factor increasing continuously...

Micromagnetic computations were performed to predict the magnetisation maps in thin elliptically shaped nanoparticles under a variable external magnetic field. Two materials were compared as the constituents of the nanoparticles: permalloy as an example of an isotropic magnet and cobalt, i.e., a hard magnetic material marked with a single easy axis...

Nanowires fabricated with experimental techniques are never perfect and possess structural imperfections. The effect of the resulting surface roughness on magnetic properties of iron nanowires has been simulated here with the use of numerical technique involving atomistic-resolved software Vampire. A two-regime or a power-law decrease in the coerci...

A hydrogen-bonded metallocyanide-based (AZE) 2 (H 3 O)[Co(CN) 6 ] framework was obtained by introducting a hydronium cation to the A 2 B(1)B(2)CN 6 -type structure. Simple K ⁺ /H3O ⁺ substitution exchange the three-dimensional structure of the double-perovskite into two-dimensional layers containing...

Four different switching scenarios have been revealed for a linear chain of flat magnetic particles with long axes perpendicular to the axis of the chain. The diamond-like shape of the particles has been previously shown to be the best to ensure a uniform and stable magnetization within a single particle, that is, to behave as a macrospin. The occu...

The equilibrium magnetization of flat elongated magnetic nanoparticles of different shapes has been determined for a range of the static magnetic fields applied parallel to their long/easy axes. The behaviour of single particles has been compared with that of equidistant chains composed of the same particles. The shapes sharpened at the ends, i.e....

Periodic systems of magnetic nanoparticles are now of interest as they support GHz spin waves. Their equilibrium configurations, switchable with the external magnetic field, are crucial for such applications. We study infinite and finite chains of particles of two shapes (i) ellipsoidal and (ii) rectangular stripes with long axes perpendicular to t...

Molecular-ionic crystals, which are built of organic cations and discrete anionic components with AMX4 stoichiometry, easily induce structural order-disorder transitions. These phenomena can generate interesting ferroic properties. Herein, we have synthesized and characterized a novel molecular-ionic crystal, (C8H20N)[BF4] (1). Thermal analysis, (D...

The single-crystals of mixed (C3H5N2)2[KFexCo1−x(CN)6] crystals, with different ratios of x = 0, 0.29, 0.42, 0.51, 0.63, 0.70, 0.85, 1, have been grown from aqueous solutions. The thermal stability of the crystals has been determined using both DTA and TGA analysis. DSC has revealed sequences of structural phase transitions (PTs). We have found fou...

Defects can significantly affect performance of nanopatterned magnetic devices, therefore their influence on the material properties has to be understood well before the material is used in technological applications. However, this is experimentally challenging due to the inability of the control of defect characteristics in a reproducible manner....

Fabrication and modeling of patterned thin films with perpendicular. [...]

The extraordinary thermally stable up to around 600 K crystals of [NH2CHNH2]3Bi2I9 (FA3Bi2I9) have been grown with the use of the evaporating method. DSC measurements have revealed reversible structural phase transitions: at 203 K (Phase I→Phase II), 173 K (II→III), 134.7 K (III→IV), 131.4 K (IV→V) and 120 K (V→VI). The crystal structures of FA3Bi2...

The purpose of this numerical study, performed within the micromagnetic framework and the dynamical matrix method, is to understand how the propagation of spin waves in a macrospin chain is affected by a configurational rearrangement of the magnetization, induced by a progressive variation of a magnetic field. Our macrospins are modelized through t...

Purpose
Brain hemodynamics is fundamental for the functioning of the human being. Many biophysical factors affect brain circulation, so that a satisfactory understanding of its behavior is challenging. We developed a mathematical model to simulate cerebral and extracerebral flows and pressures in humans.
Methods
The model is composed of an anatomi...

This paper demonstrates that an effective pitch can be attributed to acoustic signals shorter then tenths of milliseconds. A power-law dependence of this pitch on the signal's duration time is found for subjects tested with Gaussian pulses. The discrimination threshold for the pulse duration time reported on the basis of the effective pitch increas...

We present results of studies of extremely short acoustic pulses as recorded by an artificial ear in an anechoic chamber. Two types of ultrashort acoustic pulses have been used: cosine signal with the Gaussian envelope and the Gaussian envelope itself. All pulses had duration times between 0.14 ms and 27.21 ms. The recorded spectra exhibited a maxi...

Perovskite-like materials exhibit desirable photophysical and electric properties that make them suitable for a remarkable breadth of applications in electronics and physics. In this contribution, we report on the multi-phase ferroelectric and ferroelastic phenomena in pyrrolidinium-based hybrid metal-organic material, (C4H8NH2)3[Sb2Cl9]. The title...

Effects of aortic valve diseases on pressure profiles in selected locations of the human arterial system Wływ chorób zastawki aortalnej na przebiegi ciśnienia w wybranych miejscach układu tętniczego człowieka Abstract Aortic valve diseases such as aortic stenosis and aortic regurgitation, are the most frequent valvular heart diseases. The lesions i...

We have developed a numerical simulation method for predicting the time dependence (wave form) of pressure at any location in the systemic arterial system in humans. The method uses the matlab-Simulink environment. The input data include explicitly the geometry of the arterial tree, treated up to an arbitrary bifurcation level, and the elastic prop...

An anatomically detailed model consisting of a network of electric transmission lines is developed to simulate propagation of the pulse waves in humans. The simulations show that the real arterial tree geometry, together with the elastic and rheological parameters of particular segments, ensure an efficient protection of vital organs against pulse...

Stwierdzono, że bardzo krótkie impulsy akustyczne wywołują wrażenie pewnej efektywnej wysokości dźwięku. Wysokość ta maleje z czasem trwania impulsu w zakresie od 1 do ok. 20 ms. W obecnej pracy wykorzystano impulsy o kształcie funkcji Gaussa. Czas trwania określono jako podwojony parametr dyspersji rozkładu Gaussa. Wykonano badania behawioralne, k...

The present study aims to study the new method for estimating the pressure profiles during embolus
(particle) transport in arteries. The probability of the embolism in various segments of the arterial tree using the
Monte Carlo Method has been calculated. This probability is related to the size of the particle and the size of the
embolus changes fr...

9 ] (ImIB), have been synthesized and characterized in a wide temperature range (100–350 K) by means of X-ray diffraction, dielectric spectroscopy, proton magnetic resonance (1 H NMR), FT-IR spectroscopy and optical observations. They undergo two temperature induced solid–solid structural phase transitions. The first one, quasi-continuous (with tem...

Two hybrid crystals imidazolium iodoantimonate(iii) and iodobismuthate(iii), (C3H5N2)3[Sb2I9] (ImIA) and (C3H5N2)3[Bi2I9] (ImIB), have been synthesized and characterized in a wide temperature range (100-350 K) by means of X-ray diffraction, dielectric spectroscopy, proton magnetic resonance (¹H NMR), FT-IR spectroscopy and optical observations. The...

Okresowe zmiany amplitudy w wyniku nałożenia się dwóch fal nazywamy dudnieniami.
W przypadku fal akustycznych, zjawisko dudnień między innymi wykorzystuje się do strojenia instrumentów
muzycznych. Im mniej oscylacji amplitudy tym bardziej zbliżone są do siebie częstotliwości poszczególnych fal.
Zatem gdy częstotliwości fal są identyczne, w wyniku i...

The dispersion relations of axisymmetric surface waves are studied for the inner surface of a cylindrical borehole in an isotropic elastic medium coated with a thin layer satisfying equations of motion of the Kirchhoff–Love plate model. It is shown that up to three surface waves can exist, depending on the parameters of the system, in addition to a...

Dipyrazolium iodide triiodide, [C3N2H5(+)]2[I(-)·I3(-)], has been synthesized and studied by means of X-ray diffraction, differential scanning calorimetry, dielectric measurements, and UV-Vis spectroscopy. Two reversible, solid-solid phase transitions (Imma (I) ↔ (II) ↔ Pbam (III)) at 254 K and 182/188 K respectively have been revealed. The anionic...

The dynamics of the inner surface of an infinitely long circular-cylindrical cavity in an isotropic elastic medium is studied in the whole range of the Poisson's ratio including negative values characteristic of auxetic materials. The existence of the unique long-lived propagation mode (true surface wave, TSW) has been confirmed on the clean surfac...

The Helmholtz wave equation is derived for longitudinal waves in an elastic plate of arbitrary thickness placed in a rigid gantry ensuring a constant width. The whole range of Poisson's ratio allowed for isotropic elastic media constrained in this way is considered. The wave speed is shown to increase under a constant longitudinal compressive stres...

Propagation of infinitely-lived true surface waves (TSW) and of the evanescent surface resonances (pseudo surface waves, PSW) on the inner surface of a cylindrical cavity in an elastic medium coated with a thin elastic membrane is studied. An analogous flat surface with the same coating is considered as a reference system. The dispersion relations...

The human hearing sense is an astonishingly effective signal processor. Recent experiments [1, 2, 3] suggest that it is even capable of overcoming limitations implied by the time-frequency uncertainty relation. The latter, mostly known from quantum mechanics, requires that the product of uncertainties in time and frequency, Δt∙Δf , cannot be smalle...

The dispersion relations of axisymmetric surface waves are studied for the inner surface of a cylindrical borehole in an isotropic elastic medium coated with a thin layer satisfying equations of motion of the Kirchhoff–Love plate model. It is shown that up to three surface waves can exist, depending on the parameters of the system, in addition to a...

The tests accessible on the website cited in the references demonstrate that a pitch, i.e. a representation of a characteristic or dominating frequency, can be attributed to purely Gaussian submilisecond pulses. A power-law dependence of this effective pitch on the signal's duration time is found for the subjects tested. The discrimination threshol...

The enclosed tests demonstrate that an effective pitch can be attributed to
acoustic signals shorter then tenths of milliseconds. A power-law dependence of
this pitch on the signal's duration time is found for subjects tested with
Gaussian pulses. The discrimination threshold for the pulse duration time
reported on the basis of the effective pitch...

A model consisting of a string embedded in an elastic medium and terminated by a harmonic oscillator has been studied in the frequency and time domains to elucidate the physical effects of supersonic and subsonic leaky waves as well as that of true surface waves. A supersonic leaky wave manifests itself by a resonant maximum of the local density of...

A model based on the crystallographic data on dimethylammonium nonachlorodiantimonate (DMACA) is constructed. Gradual orientational ordering of three inequivalent sublattices of the dimethylammonium cations is shown to be at the origin of the anomalous behaviour of the spontaneous polarisation in this material. A quantitative comparison with the ex...

A practical method is developed to determine the strain dependence of the pseudospin–pseudospin interaction parameters in discrete models of the continuous order–disorder improper ferroelastic phase transitions from experimental data on the primary order parameter (polarisation). The temperature dependence of the mechanical strain can be then deduc...

1-Aminopyridinium iodide (API) undergoes a reversible first-order phase
transition (PT) II → I at 384 K. The single-crystal X-ray
diffraction studies have been carried out at 110, 280 and 401 K. The
compound crystallizes in the monoclinic space group P21/c
(phase II) and exhibits ferroelastic properties. High temperature
paraelastic phase (I) is de...

The equations of state for two uniaxial systems: the first with the polar direction identical with one of the crystallographic axes and the second with the polar direction within a crystallographic plane giving a realistic Curie–Weiss constant ratio and the experimentally obtained non-classical critical exponents are used to describe the behaviours...

The axisymmetric true surface waves (infinitely lived) and surface leaky waves (showing finite lifetime) have been found on the inner surface of an infinitely long cylindrical cavity in an isotropic elastic medium with various Poisson's ratios. An analogue of the Rayleigh wave turns out to transform into a bulk wave skimming surface in the long wav...

A method is devised of extracting the explicit form of the coupling between the primary and secondary order parameters with the use of experimental data and respecting classical and non-classical values of the effective critical exponents. The corresponding equation of state stems from the Ising model on a compressible lattice treated within the me...

A simple model of a surface of a 2D continuum is shown to exhibit subsonic and supersonic surface resonances (leaky waves, pseudosurface waves), i.e. finite-lived excitations, along with usual surface waves (true subsonic surface waves). The physical meaning, controversial in the existing literature, of the surface leaky waves in both regions is di...

We demonstrate that a surface resonance (pseudosurface wave) may transform into a true surface wave, i.e., acquire an infinite lifetime, at a single isolated point within a bulk band (radiative region) in a model of a stressed auxetic material. In contrast with the secluded supersonic elastic surface waves, the one found here does not belong to a d...

A scaling equation of state giving a realistic ratio of Curie–Weiss constants and accounting for coupling of the order parameter with a strain (secondary order parameter) is used to describe the temperature dependence of the electric susceptibility in an external biasing field applied in case of uniaxial ferroelectrics. Explicit expressions for the...

True surface wave, i.e. a resonance with infinite lifetime is found within a bulk band in a model of thin planar layer coating a continuous auxetic substrate. Conditions for the existence of this wave are given.

We report combined density functional studies and thermodynamic considerations on Ti-related and native defects in lithium borohydride and sodium alanate. Ti atoms introduced into the bulk of LiBH(4) are thermodynamically unfavorable for all their oxidation states, while high oxidation states of Ti(n+) cations may become thermodynamically stable in...

Two novel guanidinium iodoantimonate(III) and iodobismuthate(III) crystals, [C(NH2)3]3[Sb2I9] and [C(NH2)3]3[Bi2I9], have been synthesized and their structures have been determined by means of single-crystal x-ray diffraction studies at three temperatures (293, 348 and 362 K). Both compounds appeared to be isomorphous in corresponding phases. The c...

A model of an artery consisting of a thin-walled flexible tube filled with a Newtonian incompressible liquid and surrounded by an external viscoelastic tissue is studied. The dispersion relations and attenuation lengths are determined for the lowest axially symmetric propagation modes: the Young, Lamb, and torsional modes. The numerical calculation...

Scaling hypothesis is used to construct the equations of state that provide the experimentally observed variety of the Curie--Weiss constants ratios (i.e., the ratios of the slopes between the temperature dependencies of inverse of susceptibility below and above the critical point) in uniaxial ferroelectrics. The results are exemplified by the TGS...

Equations of motion for an anharmonic interface separating two dispersionless
1-d media are shown to be equivalent to those of the Duffing oscillator coupled
with an overdamped harmonic oscillator. Transmission and reflection coefficients
as well as trapping times are numerically determined for the most representative
sets of the model paramete...

The real part of the complex electric permittivity at low frequencies and at several biasing fields (between 0 and 5×105V/m ) has been measured in ferroelectric crystals [CH3NH3]5Bi2Cl11 (MAPCB) and [CH3NH3]5Bi2Br11 (MAPBB) in the temperature range covering the temperature of the ferroelectric phase transitions. Comparative measurements for the kno...

The general shape of the temperature dependence of the static susceptibility in a biasing field conjugated to the order parameter is analysed with the use of the simplest equation of state compatible with the Widom and Griffiths scaling hypothesis. The corresponding curves are demonstrated to show from two to four inflection points, from which a di...

A surface wave of frequency lying within bulk band of transverse waves is found in an elastic medium coated with a thin layer endowed with a surface mass density, surface Young's modulus and surface bending modulus. The wave is a particular case of surface resonance with infinite lifetime. In materials with negative Poisson's ratio (auxetics) the w...

p>The simplest scaling equation of state and its limit case corresponding to the Landau theory turns out to accurately describe the temperature dependence of the electric susceptibility measured in a biasing static field (Nonlinear Dielectric Effect NDE) in uniaxial ferroelectrics. The same equation of state should be, in principle, valid at the ze...

The dispersion relations, involving attenuation parameters, are given for the lowest modes of propagation in a model of artery consisting of a cylindrical, elastic, thin-walled tube filled with a Newtonian viscous liquid and placed in a medium showing elastic stiffness and internal damping. The amplitudes of the modes generated by the most plausibl...

A generalized model of a solid-solid interface is built. The model takes into account additional surface mass densities on both sides of the interface and an anisotropic and/or anharmonic coupling potential. The resonances due to the potential (up to three) manifest themselves by minima (zeros) of transmition and/or extrema in reflected and transmi...

The simplest equation of state compatible with the Widom and Griffiths scaling hypothesis have been built for the uniaxial ferroelectrics TGS and MAPCB. The explicit forms have been found of the scaling invariants deduced from the curves of the electric susceptibility measured in a constant biasing field. Smooth and sharp inflection points of the s...

Simple structures enabling the multiplexing of acoustic waves are presented. Such structures are constructed out of two monomode acoustic wires and two masses bound together, and to the wires by springs. We show analytically that these simple structures can transfer with selectivity and in one direction one acoustic wavelength from one wire to the...

The crystal structure of the pyrrolidinium hexachloroantimonate(V), [C4H8NH2][SbCl6], abbreviated PCA, has been determined by means of X-ray diffraction at 300 and 340 K. The space groups are monoclinic P21/n (phase III) and orthorhombic Pmnb (phase II), respectively. The crystal undergoes two structural phase transitions: first-order type at 356/3...

A system of equations of motion for the Green functions in layered antiferromagnets such as La2CuO4 and YBa2Cu3O6 has been treated by an “equal access” decoupling scheme. The correlation functions are fully equivalent in this scheme in contrast with the ordinary random-phase approximation (RPA). The method provides a new insight into the nature of...

Delayed differential equation of motion is derived for an anharmonic resonator coupled to a monomode transmission line. Transmission and reflection coefficients are found analytically in the harmonic approximation. Nonlinear response of the system is analysed by an electric circuit obeying the same equations of motion. An aperiodic (chaotic) respon...

A multiplexing system which consisted of two discrete plasmon wires coupled by two metal nanoclusters was discussed. It was observed that the directional plasmon ejection was optimized by closed-form relations between the transmission coefficients and the nanocluster distances. An oscillating dipole field was produced by the plasmon excitations, wh...

Simple multiplexing phonon structures are presented. Such structures can be deposited on a surface with current ultra-high vacuum technologies. In the atomic domain they are supposed to be made out of two parallel mono-atomic chains of atoms and of a simple coupling device made out of two other atoms interacting together and with the two chains. We...

We present a simple multiplexing device made of two atomic chains coupled by two other
transition metal atoms. We show that this simple atomic device can transfer electrons at a
given energy from one wire to the other, leaving all other electron states unaffected.
Closed-form relations between the transmission coefficients and the inter-atomic dist...

Effective equations of motion of a surface atom placed in an anharmonic surface potential are derived for three kinds of substrates (i) continuous dispersionless, (ii) discrete with nearest neighbours harmonic interactions, and (iii) a substrate showing a strong spatial dispersion. The resulting equations of motion are differential equations in the...

A four-state pseudospin model for the isomorphous phase transition in mixed crystal C70(1-x)C60x is shown to be equivalent to a two-state Ising model with one state degenerate. The model predicts a metastable disordered phase corresponding to a glassy state. The effect of random fields and random bonds is to drive the system towards the critical po...

Delayed differential equation of motion with multiple lags is derived for an anharmonic stub resonator coupled to a monomode
transmission line. Transmission and reflection coefficients are found analytically in the harmonic approximation. Nonlinear
response of the system is analysed by an electric circuit obeying the same equations of motion. Enhan...

Energy transfer coefficient (analogue of LDOS) and aperiodicity index are defined to characterise the nonlinear response and the surface resonances in a thin layer separated from the underlying bulk crystal by an anharmonic interface. Regions of periodic, aperiodic and intermittent motion of the system are found by analysing the electric circuit ob...

The low symmetry phases and the related soft modes are found for symmetry breaking equitranslational phase transitions of cubic media. The existence of the only possible longitudinal soft modes is predicted in two corners of the stability triangle. The phase velocities of soft modes are expressed by eigenvalues of the tensor of elastic constants.

Mean-field static susceptibility χE at constant measuring field E is found to follow the law χE−1=B1/3E2/3+(a/3)(T−Tc) at T>Tc and χE−1=B1/3E2/3+B1/6E1/3[a(Tc−T)]1/2 at T

: A four-state pseudospin model is constructed for the isomorphous phase transition hcp-2↦hcp-1 in pure C70 and in C70-rich mixed crystal C
70(1 - x)
C60x. With the specific anisotropic pseudospin interactions adapted to the C70 crystal the model is equivalent to a two-state Ising model in a temperature-dependent field. Replica symmetric state of...

Soft X-ray diffraction from synchrotron radiation gives access to the use of MAD (multi-wavelength anomalous diffraction) and DAFS/DANES (diffraction anomalous fine structure/diffraction near edge structure) methods with relatively light elements down to Z=14 (silicon), including elements such as sulfur and phosphorus essential in life. It also exp...

A new piperidinium chloroantimonate-(V) analogue, (C5H10NH2)SbCl6 has been studied by means of single-crystal
x-ray diffraction, differential scanning calorimetry, thermal expansion and
dielectric techniques. It undergoes three solid-solid state phase
transitions: at 363 K first order (from Cmcm (phase I) to Cc (phase II)),
at 310 K second order (f...

A two-sublattice peudospin model with distance-dependent interaction parameters is constructed for the ferroelectric phase transition at 307 K and for the isomorphous anomaly at 180 K in pentakis (methylammonium) undecachlorodibismuthate (III) (CH3NH3)5Bi2Cl11. A series of Monte Carlo simulations involving continuous degrees of freedom of deformati...

Elastic and acoustic properties of all cubic materials are classified
with the use of a stability triangle in a 2D subspace of elastic
parameters. The behavior of bulk modulus B, shear modulus Cs,
Poisson's ratio σp and anisotropy parameter η is
studied in the vicinity of characteristic lines of this triangle -
mechanical stability borders and line...

The composite materials with two interfaces studied here are formed out of one slab sandwiched between two other semi-infinite crystals. The corresponding response function is obtained in closed form for a simple phonon model of simple cubic crystals. Knowledge of this function enables the authors to study all the vibrational properties of such a s...

Anomalous diffraction with soft X-ray synchrotron radiation opens new possibilities in protein crystallography and materials science. Low-Z elements like silicon, phosphorus, sulfur and chlorine become accessible as new labels in structural studies. Some of the heavy elements like uranium exhibit an unusually strong dispersion at their M(V) absorpt...

The feasibility and a review of progress in the long-wavelengths anomalous dispersion technique is given in the context of the development of beamline ID1 of the ESRF for such studies. First experiments on this beamline and their analyses are described. The first study reports on the use of uranium which exhibits an unusually strong anomalous dispe...

Effective equations of motion for anharmonic defects in harmonic media are Volterra integro-differential equations (VIDE). In the special case of dispersionless one-dimensional harmonics substrates they reduce to differential equations. Efficiency of harmonic generation, phonon reflection coefficients, effective local density of states, regions of...

The effective equations of motion for a surface atom in an anharmonic surface potential have been derived for dispersionless
one-dimensional substrates. The system is equivalent to a non-linear damped oscillator (Duffing oscillator) with the forcing
term depending on the form of the incident wave. Efficiency of harmonics generation, phonon reflecti...

A two-sublattice compressible pseudospin model has been constructed to describe the behaviour of the spontaneous polarisation of PMACB in the temperature region comprising the ferroelectric phase transition (T=307K) and the isomorphous anomaly (T= 180 K). A strong coupling of pseudospins with a “pancake” strain -(2$epsilon$33 - $epsilon$11 - $epsil...

Explicit expressions are given for the effective equations of motion for surface atoms placed in a general anharmonic potential and attached to semi-infinite harmonic bulk substrates. Three types of one-dimensional substrates are considered: i) continuous dispersionless, ii) discrete with nearest neighbours harmonic interactions, and iii) a substra...

The effect of strong spatial dispersion of the substrate crystal onto the dynamics of thin epitaxially adsorbed films is described in a simple model through the following quantities: i) phonon reflection coefficients ii) depth-dependent local densities of states (LDOS) and iii) finite-life-time surface states called leaky waves. The correspondence...

The explicit formulae for the Green functions are given for the bulk crystal, for a crystal with surface and for finite-thickness thin layers adsorbed on a surface as a function of microscopic interaction parameters. The case of the (001)Fe surface and of epitaxial layers of W on the same surface is studied on the basis of the experimental dispersi...

A phenomenological model is proposed to describe the sequence of phase transitions in Pentakis (methylammonium) Undecachlorodibismuthate (III), (CH3NH3)5Bi2Cl11 (PMACB) crystal on the basis of the recent structural data. The ferroelectric phase transition at 307 K is attributed to the ordering in a sublattice of the methylammonium cations CH3NH+3 p...

Benzil (C6H5—CO)2 exhibits an order - disorder phase transition at Tc = 83.5 K, which leads the crystal from trigonal (P3121, Z = 3) high temperature phase to a monoclinic (P21, Z = 6) low temperature phase. We present the detailed low frequency (1 Hz) elastic measurements and thermal expansion data from 77K to 90K
The thermal expansivity shows onl...

The molecule of benzil (diphenylethanedione, C14H10O2) has been approximated by a system of rigid segments to model the lowest-frequency part of its vibrational spectrum. The interactions of internal degrees of freedom have been described with the use of phenomenological force constants. The structure of the trigonal (P3121) phase has then been mod...

After a brief review on surface phonons, we focus on resonant phonons in adsorbed thin layers. Such resonances may in general be understood within the substrate bulk band as thin layer modes shiften and broaden by the interaction with the substrate phonons. These resonant phonons appear as well-defined peaks in the phonon density of states. Their e...

The anomalous temperature dependence of the volume, of the spontaneous tetragonal strain, and of the orientational order parameter, observed experimentally at about 408 K within the tetragonal phase of KHF2 is described with the use of a phenomenological theory based on the symmetry of the crystal. The relations among the coefficients of the free e...

The crystallographic structure and the distribution of orientations of molecular ions are studied near the surface in an orientationally disordered crystal with the use of a Green-function formalism. The orientational degrees of freedom are treated by means of symmetry-adapted functions of angular coordinates. The structure of the (001) surface of...