Zbigniew Koziol

• PhD
• Professor (Assistant) at National Center for Nuclear Research

W and W-based high-entropy alloys (HEAs) are promising candidates for plasma-facing materials in fusion reactors. While irradiation studies on W have revealed a tendency for helium (He) bubble formation and radiation-induced defects, investigations of WTaCrV HEA have demonstrated superior radiation resistance, whether under He+ irradiation or heavy...

The model of chain of springs and masses, originating from works of Schr\"odinger (1914) and Pater (1974), is found suitable as an analytical description of dynamics of layers in oriented FCC crystals. An analytical extension of that model has been provided for the case of linear-in-time ramp pressure applied to sample surface. Examples are provide...

Anharmonic inter-atomic potential ∼|x|n , n > 1, has been used in molecular dynamics (MD) simulations of stress dynamics of FCC oriented crystal. The model of the chain of masses and springs is found as a convenient and accurate description of simulation results, with masses representing the crystallographic planes. The dynamics of oscillations of...

Anharmonic inter-atomic potential ∼ |x|^n , n > 1, has been used in molecular dynamics (MD) simulations of stress dynamics of FCC oriented crystal. The model of chain of masses and springs is found as a convenient and accurate description of simulation results, with masses representing the crystallographic planes. The period of oscillations of two...

Molecular dynamics simulations provide information on atomic displacement cascades due to the ionic collisions on the time scale of picoseconds and simultaneously account for the effects of crystal structure and temperature. Thus, molecular dynamics can help to understand the specific material behaviour during ion irradiation and make predictions f...

Movement of line dislocations in fcc steel 310S is found to depend on the size of nanometer sized structures, based on modeling within molecular dynamics (MD). The effect is attributed to time (and size) dependencies of pressure propagation into the medium interior. The observation is crucial in interpreting any MD studies of pressure effects since...

Movement of edge (line) dislocations in FCC steel 310S is shown to depend on the size on nanoscale structures, based on modeling withing molecular dynamics (MD). The effect is attributed to time (and size) dependencies of pressure propagation into the medium interior. The observation is crucial in interpreting any MD studies of pressure effects sin...

We present a general-purpose numerical quantum mechanical solver using Schrödinger-Poisson equations called Aestimo 1D. The solver provides self-consistent solutions to the Schrödinger and Poisson equations for a given semiconductor heterostructure built with materials including elementary, binary, ternary, and quaternary semiconductors and their d...

Supplementary material to "Number of equidistant neighbors on honeycomb lattice." It contains description of provided example, simple scripts for computing quantities discussed in the paper. Is someone is interested in using indeed the method than these scripts might be very useful.

A convenient scheme is presented for calculating potential energy of van der Waals interacting bilayer graphene and other similar 2D compounds. It is based on the notion of the existence of two types of local symmetry of carbon atoms ordering, a 3- and 6-fold one. Potential energy of an atom is expressed as a sum of contributions from rings of equi...

A convenient scheme is presented for calculating potential energy of van der Waals interacting bilayer graphene and other similar 2D compounds. It is based on the notion of the existence of two types of local symmetry of carbon atoms ordering, a 3- and 6-fold one. Potential energy of an atom is expressed as a sum of contributions from rings of equi...

The experimental knowledge on interlayer potential of graphenites is summarized and compared with computational results based on phenomenological models. Besides Lennard-Jones approximation, the Mie potential is discussed, Kolmogorov-Crespy model and equation of Lebedeva et al. An agreement is found between a set of reported physical properties of...

The experimental knowledge on interlayer potential of graphenites is summarized and compared with computational results based on phenomenological models. Besides Lennard-Jones approximation, the Mie potential is discussed, Kolmogorov-Crespy model and equation of Lebedeva et al. An agreement is found between a set of reported physical properties of...

Activity of users on Internet discussion forums is analyzed. The rank of users is shown to be approximated better by stretched-exponential function than by the Zipf law. Cumulative distribution function is found as an excellent tool in analysis of the dynamics of the collective social phenomena. We are able to approximate the number of blog comment...

Computer simulations with Synopsys' Sentaurus TCAD are used to study the ef-fect of the molar concentration of aluminum in the active and waveguide regions on the energy spectrum of carriers in Quantum Well (QW) and the optical spectral character-istics of radiation of semiconductor lasers with AlxGa 1−x As double heterostructures and separate conf...

Activity of users on Internet discussion forums is analyzed. The rank of users is shown to be approximated better by stretched-exponential function than by Zipfs law. Cumulative distribution function is found as an excellent tool in analysis of the dynamics of the collective social phenomena. We are able to approximate the number of blog comments w...

Drift-diffusion computer simulation model available in Synopsys’ Sentaurus TCAD User Guide is used to study electrical and optical characteristics of a separate-confinement heterostructure laser based on AlGaAs. We investigate the role of the width and depth of quantum-well active region, below and above the lasing threshold. The device properties...

Drift-diffusion computer simulations model available in Synopsys' Sentaurus TCAD is used to study electrical, I-V, and optical, I-L, characteristics of separate-confinement heterostructure laser based on $AlGaAs$. We investigate the role of the width and depth of Quantum Well (QW) active region, below and above the lasing threshold. The device prop...

A method has been developed for measuring and analysing the complex ac susceptibility of a metal undergoing a superconducting transition, in case there exists an interplay between the normal-state skin-effect and the response characteristic for the superconducting state. For the unconventional superconductor UPt3, the study of the temperature and f...

Computer simulations with Synopsys' Sentaurus TCAD of opto-electrical characteristics of separate-confinement heterostructure laser based on AlGaAs are used as an example to study the role of the width and depth of Quantum Well (QW) active region on laser characteristics, I-V and I-L, below and above the lasing threshold. The device properties depe...

Optical and electrical characteristics of AlGaAs lasers with separate confinement heterostructures are modeled by using Synopsys's Sentaurus TCAD, and open source software. The results for cases of 2-QW (2 Quantum Wells) and 3-QW structures are compared with these for 1-QW. A significant improvement of useful laser parameters is obtained by increas...

Optical and electrical characteristics of AlGaAs lasers with separate confinement heterostructures are modeled by using Synopsys's Sentaurus TCAD, and open source software. We propose a modified exponential $I-V$ dependence to describe electrical properties. A simple analytical, phenomenological model is found to describe optical efficiency, $\eta$...

Optical and electrical characteristics of AlGaAs lasers with separate confinement heterostructures are modeled by using Synopsys's Sentaurus TCAD and open source software for semi-automatic data analysis of large collections of data. The effects of doping in all laser layers are investigated with the aim to achieve optimal characteristics of the de...

At present, one of the progressive methods for studying physical processes is the method of their simulation using modern specialized computer programming tools. One of these tools is the Sentaurus TCAD software environment from Synopsys designed for device-technological simulation of semiconductor devices. The book considers the main features of u...

Key characteristics of an AlGaAs semiconductor laser with separate confinement heterostructures (SCH) as functions of the active region position in waveguide are investigated by the methods of computer simulation in the Synopsys’ Sentaurus TCAD software. It’s shown that the power conversion efficiency of lasers with asymmetric structure where activ...

Influence of Al concentration in the waveguide and emitter regions of a AlGaAs semiconductor laser with separate confinement heterostructures (SCH) on the laser I-V- and light-current-curves is investigated by the methods of computer simulation in the Synopsys’ Sentaurus TCAD software. The optical efficiency of the laser and vertical divergence of...

The mathematical model for analytical calculations of the radiation wavelength of a AlGaAs semiconductor laser with separate confinement heterostructure (SCH) and quantum well active region is presented. Influence of the aluminium mole concentration in active and waveguide regions on the energy spectrum of carriers and spectral characteristics of t...

Computer simulations with Synopsys' Sentaurus TCAD are used to study the effect of the molar concentration of aluminum in the active and waveguide regions on the energy spectrum of carriers in Quantum Well (QW) and the optical spectral characteristics of radiation of semiconductor lasers with AlxGa1-xAs double heterostructures and separate confinem...

The influence of Fe substituted for Cu in YBa2Cu3O7−δ on the intra- and intergrain properties has been studied. In the concentration regime 0 ≤ x ≤ 0.02 the intragrain critical current density slightly increases with increasing concentration of iron, but for x ≥ 0.04 it drops significantly. On the contrary, the intergrain critical parameters are gr...

The effect of minor changes in lattice parameters and ratios on the magnetoresistive and related properties of the La - Er - Ca - Mn - O perovskite system have been investigated. The latter is found to be the more important factor in determining the magnetotransport properties of these materials. One composition has been prepared by both the standa...

Magnetotransport and magnetic properties of the system La0.6M0.07Ca0.33MnO3 (M  Er, Yb, Bi) have been investigated. The behavior of the three samples varies much more than might be expected on the basis of the similarity in ionic radii of M3+ ions and a small quantity of the substitution. A strong correlation is found between magnetization data, F...

The ac response of a slab of material with electrodynamic characteristics E∼j^κ+1, κ≥0, is studied numerically. From the solutions of the nonlinear diffusion equation, the fundamental and higher‐order components of the harmonic susceptibility are obtained. A large portion of the data for every κ can be scaled by a single parameter, ξ≡t<su...

The temperature and applied magnetic field dependence of the resistivity of icosahedral Al 50 Pd 10 Mn 25-x Fe x B 15 (x=0 and 5) alloys has been measured between 4.2 and 300 K. At low temperature, T≪30 K, the resistivity showed a rapid decrease with increasing temperature and may be described by a combination of weak localization (WL) and magnetic...

The magnetic susceptibility, magnetization and the temperature and field dependence of the Hall coefficient have been measured for the magnetically ordered icosahedral quasicrystals Al 70–x Pd 15 Mn 15 B x (x=0,2,4,6,8,10). The temperature dependence of the real and imaginary part of the complex ac susceptibility indicates re‐entrant magnetic behav...

In many cases, the critical‐state theory can be treated as a sufficiently accurate approximation for the modeling of the magnetic properties of superconductors. In the present work, the magnetostrictive hysteresis is computed for a quite general case of the modified Kim–Anderson model. The results obtained reproduce many features of the giant magne...

In many cases, the critical-state theory can be treated as a suffi ciently accurate approximation for the modelling of the magnetic properties of superconductors. In the present work, the magnetostrictive hysteresis is computed for a quite general case of the modified Kim-Anderson model. The results obtained reproduce many features of the giant mag...

Using the Hall-probe technique, the magnetization anisotropy of URu2Si2 was studied as a function of magnetic field and temperature. The flux-pinning force, Fp(T, H), is anisotropic and for H‖a-axis turns out to be strongly enhanced at large field. The temperature dependence of Hc2 reveals the unusual nature of this compound: an unconventional orde...

In many cases, the critical-state theory can be treated as a suffi ciently accurate approximation for the modelling of the magnetic properties of superconductors. In the present work, the magnetostrictive hysteresis is computed for a quite general case of the modified Kim-Anderson model. The results obtained reproduce many features of the giant mag...

AC susceptibility measurements have been carried-out on single-crystalline samples of UPt3 doped with 11% boron. The low-amplitude susceptibility is nearly independent on the ac field amplitude and, hence, it is related to the low-frequency complex conductivity. At large ac field, strong nonlinearities characterize the electrodynamic response. The...

Using a sensitive Hall-probe technique, the magnetization anisotropy of the heavy-fermion superconductor URu₂Si₂, with T_c=1.2 K, was studied as a function of magnetic field and temperature on a cube-shaped sample. The estimated first-critical-field values, H_c1, extrapolated to T=0 are about 10 and 15 Oe...

We report on the magnetization of the heavy-fermion superconductor UNi₂Al₃ measured at 1.5 and 4.2 K in magnetic fields up to 35 T. The results indicate in-plane type of magnetocrystalline anisotropy. At both temperatures, almost linear magnetization curves up to the highest field applied are found. In 35 T, we obtained magnet...

A commercial Hall probe (supplied by Lake Shore Cryotronics, Inc.) is used as a sensor of the magnetic field at the surface of a magnetized sample. With the Linear Research resistance bridge LR-400, an excellent stability, linearity of response on field and an extremely small temperature dependence of the background signal is obtained, which is ess...

A non-logarithmic time dependence of the magnetization relaxation in superconductors is modeled by certain solutions of the nonlinear equation for flux diffusion, which can be derived either on the assumption of a logarithmic dependence of the pinning potential on the current density or, equivalently, a power-law current-voltage characteristic. Lim...

The influence of substitutions on the superconductivity in the systems (U1-xYx)Pt3, (U1-xThx)Pt3, and U(Pt1-xPdx)3 have been studied by resistance and specific-heat measurements for T < 1 K. The results of yttrium and thorium substitution are discussed in terms of the models developed by Hirschfeld et al. and Schmitt-Rink et al. in which the power...

Using a sensitive Hall probe, the magnetization relaxation of Bi2Sr2CaCu2O8 single crystals has been measured accurately. The sample was cooled down from T>Tc in a large bias magnetic field and then relaxation has been registered after a small change of the magnetic field. The effects of the bias field value, ranging from almost zero up to Hirrev (...

Using a sensitive Hall probe, the remanent magnetization of Bi2Sr2CaCu2O8 single crystals has been measured accurately as a function of temperature. The interpretation of the results is based on the modified Kim-Anderson critical-state model. An explanation of some of the commonly observed history dependencies is proposed, as well as the finite val...

A method has been developed for measuring and analysing the complex ac susceptibility of a metal undergoing a superconducting transition, in case there exists an interplay between the normal-state skin-effect and the response characteristic for the superconducting state. For the unconventional superconductor UPt3, the study of the temperature and f...

Low-field AC susceptibility measurements have been carried-out on single-crystalline samples of the unconventional superconductor UPt3 and on UPt3 doped with 11% boron. Both components of the susceptibility, chi' (T) and chi'' (T) have been found to depend strongly on the AC field amplitude, on the superimposed DC field (up to 200 Oe), and on the o...

Measurement on the resistive transition of YBa2Cu3O7 and Bi2Sr2CaCu2O8 single crystals have been performed at various temperatures with magnetic fields rotating from the c-axis to the ab-plane. The results are discussed in terms of flux-flow with the anisotropy of the upper critical field. Deviations from the theory are found for field directions c...

Experiments have been performed on the unconventional superconductor UPt3 close to Tc. Topics that have been studied are: the double-step transition in the specific heat, the anisotropy in the enhanced conductivity above Tc and the low field ac susceptibility. A double-step structure has been observed in chi(T) as well for the ac field parallel to...

Superconducting UPt 3 is characterized by a novel and complex magnetic field‐temperature phase diagram, with two superconducting transitions at T c1 and T c2 in zero field. We have studied the effects of Pd and Y impurities on the zero field superconducting properties of UPt 3 . Resistance measurements show that both dopants increase the residual r...

The low field complex ac susceptibility of the ceramic high - Tc superconductors has been investigated close to Tc for frequencies from 1.75 kHz to 56 kHz. There is shown that the critical state model is not sufficient for description of the results. Analysis of the data suggests the existence of the relaxation processes which manifests in strong f...

Superconducting UPtâ is characterized by a novel and complex magnetic field-temperature phase diagram, with two superconducting transitions at {ital T}{sub {ital c}1} and {ital T}{sub {ital c}2} in zero field. We have studied the effects of Pd and Y impurities on the zero field superconducting properties of UPtâ. Resistance measurements show that b...

The influence of irradiation by fast neutrons with fluences from 3.3 x 1016n/cm2 up to 3 x 1018n/cm2 on the physical properties of polycrystalline Bi0.7Pb0.3SrCaCu1.8Ox was examined. Studies of DC magnetization, AC susceptibility, transport and thermoelectric power were performed. The irradiation caused a decrease of Tc, determined from the onset o...

The influence of Fe substituted for Cu in YBa2Cu3O7−δ on the intra- and intergrain properties has been studied. In the concentration regime 0; x; 0.02 the intragrain critical current density slightly increases with increasing concentration of iron, but for x; 0.04 it drops significantly. On the contrary, the intergrain critical parameters are gradu...

The AC complex magnetic susceptibility of the ceramic Y1Ba2Cu3O7−δ was measured close to the superconducting transition temperature as a function of a superimposed DC field and frequency of the AC field. Temperatures TJ of the maxima of the imaginary part of the susceptibility are connected with the occurence of the phase locking of the grains orde...

The complex susceptibility of high Tc superconductor YBa2Cu3O7–δ is measured as a function of temperature, for different values of ac field amplitude and dc field. The measurements are carried out on ceramic and powdered samples. Moreover, the dependences of lower critical fields upon the temperature measured by the dc susceptometer are presented....

The AC complex magnetic susceptibility of the ceramic Y1Ba2Cu3O7-delta was measured close to the superconducting transition temperature as a function of a superimposed DC field and frequency of the AC field. Temperatures TJ of the maxima of the imaginary part of the susceptibility are connected with the occurence of the phase locking of the grains...

AC complex magnetic susceptibility of ceramic YBa 2 Cu 3 O 7- δ was measured close to the superconducting transition temperature, as a function of the amplitude of the alternating magnetic field and of a superimposed dc field. From the maxima of the imaginary part of susceptibility, the universal scaling of the dc field and the temperature dependen...

This thesis reports on the investigation of magnetic properties of heavy-fermion and high-Tc superconductors. These are two families of compounds characterized by remarkably different normal-state and superconducting properties. While interest in copper-oxide materials is driven mainly by their possible large-scale applications, heavy-fermion compo...