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Publications (72)
In this paper we focus on the new version of computer program MODY for calculations of symmetryadapted functions based on the theory of groups and representations. The choice of such a functional frame of coordinates for description of ordered structures leads to a minimal number of parameters which must be used for presentation of such structures...
A complex scheme of atomic displacements (modes) that break the Fd symmetry of the high-temperature (Tc>395 K) cubic phase of Rb0.91Nb0.96W1.04O5.98 and ultimately lead to a phase transition to the tetragonal phase was determined using the group theory approach. The resulting set of modes was used to construct a model of the disordered crystal that...
Physical properties of the Tm5Ni2In4 compound have been investigated by means of magnetometric, calorimetric as well as neutron diffraction measurements. The compound crystallizes in the orthorhombic Lu5Ni2In4-type crystal structure (space group Pbam, No. 55). The reported results indicate that the sample exhibits an antiferromagnetic ordering belo...
In this paper we focus our attention on the structural and magnetic properties of the RPdIn (R = La, Ce, Pr, Nd, Ho, Er) deuterides. The RTIn compounds having the ZrNiAl-type of crystal structure were suspected of breaking the Switendick 2 Å limit on the nearest H–H distances. As the search for new materials with extraordinarily short H–H distances...
Knowledge of how chemically predefined clusters of atoms are arranged in a crystal and how they can reorientate under external excitations is of great importance for structure determination and a description of structural transformations. In general, the probability of cluster reorientation depends on the activation energy and thus on the symmetry...
The evacuation of football stadium scenarios as examples of evolution of complex system are discussed. The models are presented as movements of individuals according to fields of displacements, calculated correspondingly to the given scenario. The assumption has been made that the most effcient evacuation is left based on the accordance of symmetry...
A powder diffraction measurement of Ho5Rh4Ge10 is reported. This compound crystallizes in the tetragonal Sc5Co4Si10-type structure (space group P4/mbm) in which the Ho atoms occupy three different sites. The neutron diffraction measurements indicate antiferromagnetic order with the Neel temperature T-N = 7 K. Below T-N an additional phase transitio...
In an emergency situation, imitation of strategies of neighbours can lead to an order-disorder phase transition, where spatial clusters of pedestrians adopt the same strategy. We assume that there are two strategies, cooperating and competitive, which correspond to a smaller or larger desired velocity. The results of our simulations within the Soci...
A powder neutron diffraction measurement of Er5Rh4Ge10 is reported. This compound crystallizes in the tetragonal Sc5Co4Si10-type structure (space group P4/mbm) in which the Er atoms occupy three different sites. The neutron diffraction measurements indicate antiferromagnetic order with the Néel temperature TN=5.5 K. Below TN an additional phase tra...
In materials science there is an increasing need for developing a robust and reliable first-principle approach capable of predicting crystal structures, by taking only the stoichiometry as an input. We integrate several methodologies to tackle this problem including quantum chemistry cluster calculations, simulated annealing algorithm for structure...
The simulation of evacuation of pedestrians from skyscraper is a situation where the symmetry analysis method and equations of fluid dynamics finds to be very useful. When applied, they strongly reduce the number of free parameters used in simulations and in such a way speed up the calculations and make them easier to manage by the programmer and w...
Symmetry analysis was applied in this work to discuss the behavior of the family R6M23 compounds upon hydrogenation (deuteration), where different structural transformations and magnetic properties, depending
on the type of R and M atoms and hydrogen (deuterium) concentrations, have been found. The crystallographic structure of these
compounds is d...
The evacuation of football stadium scenarios are discussed as model realizing
ordered states, described as movements of individuals according to fields of
displacements, calculated correspondingly to given scenario. The symmetry of
the evacuation space is taken into account in calculation of displacements
field - the displacements related to every...
Magnetic properties of a sigma-Fe16Cr14 alloy calculated with the charge- and spin-self-consistent Korringa-Kohn-Rostoker (KKR) and combined with coherent potential approximation (KKR-CPA) methods are reported. Nonmagnetic state as well as various magnetic orderings were considered, i.e., ferromagnetic (FM) and more complex antiparallel (called APM...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The magnetic ordering of HoRhSn, crystallizing in the hexagonal ZrNiAl-type structure, has been investigated by neutron diffractometry in the temperature range between 1.5 and 15.5 K. The compound has been found to order antiferromagnetically below 6 K with a magnetic structure than can be described by a propagation vector k→=[13,13,13]. By group-t...
The symmetry of magnesium borohydride Mg(BH4)2 has been analyzed. In particular, relations between space groups I41/amd(IT 141), I-4m2(IT 119) and F222(IT 22) have been derived. As a result of the analysis based on the theory of the space groups and their representations we found all transformations from the parent structure, described by the high...
The symmetry analysis method based on the theory of group representations is used for description of complex systems and their behavior in this work. The first trial of using the symmetry analysis in modeling of behavior of complex social system is presented. The evacuation of large building scenarios are discussed as transition from chaotic to ord...
A typical situation in which symmetry analysis can be applied to the description of ordering process in crystalline solids includes the following elements: a) well-defined high-symmetry phase, with a known symmetry space group, b) physical changes lowering the crystal symmetry to a subgroup of the original space group, c) local physical quantity (s...
The ground-state structure of magnesium tetrahydroborate, Mg(BH4)2, is still under debate. The experimentally and theoretically proposed structures mismatch, and even among the computationally determined structures a disagreement still exists. The main debated question is related to the lattice stability of the proposed structures. We combined seve...
In the complex metallic alloys (CMA) it is often found that some parts of the unit cell form well-defined nanoscale building blocks, called clusters, which are characterized by a specific local symmetry and separated from the 'matrix' crystal lattice by a partially disordered interface zone. The interior of the cluster is usually a close packed str...
Intermetallic compounds AB5 type (A = rare-earth atoms, B = transition metal) are known to store reversibly large amounts of hydrogen and as that are discussed in this work. It was shown that the alloy cycling stability can be significantly improved by employing the so-called non-stoichiometric compounds AB5+x and that is why analysis of change of...
Absorption of hydrogen in the intermetallic compounds of Rare Earths and Yttrium with 3-d metals causes structure distortions and transformations depending on hydrogen content and temperature. One of the most intriguing problems for the unsaturated hydrides is a tendency for ordering of hydrogen atoms. To find the explanation of the observed transf...
In this paper, the recent developments in practical applications of symmetry analysis are described. The theoretical basis shortly described in Section 1 has been implemented in several computer applications, one of which is the program “MODY-win”, developed by the authors of the paper. The program calculates the so-called basis vectors of irreduci...
The Al−Mg phase diagram has been reinvestigated in the vicinity of the stability range of the Samson phase, β-Mg2Al3 (cF1168). For the composition Mg38.5Al61.5, this cubic phase, space group Fd-3m (no 227), a = 28.242(1) Å, V = 22526(2) Å3, undergoes at 214 °C a first-order phase transition to rhombohedral β′-Mg2Al3(hR293), a = 19.968(1) Å, c = 48....
The paper describes the application of symmetry analysis to construction of possible quadrupolar ordering modes in a crystal with a given space group symmetry. The matrix representing a given tensor property (e.g. quadrupolar moment) is converted to a vector form, for which the standard symmetry analysis algorithms can be applied. The possible orde...
Bulk magnetic, x-ray, and neutron-diffraction measurements were performed on polycrystalline Tb14Ag51 in the temperature range from 1.5 K to room temperature. Its chemical Gd14Ag51-type structure corresponding to space group P6∕m has been refined at 300 and at 30 K. Combined with group-theoretical symmetry analysis, we show that the magnetic struct...
Application of symmetry analysis method to description of local tensors is presented in this paper. The method is based on the decomposition of full representation of the space group, calculated for a given wave vector k→, into its irreducible representations (IR). The final ordering pattern is built up as a linear combination of basis vectors (BV)...
Bulk magnetic, X-ray and neutron diffraction measurements were performed on polycrystalline Tb14Ag51 in the temperature range from 1.5 K to room temperature. Its chemical Gd14Ag51 type structure corresponds to space group P6/m. Combined with group theoretical symmetry analysis, we show that the magnetic structure of this intermetallic compound is o...
This paper describes a computer program, based on the theory of groups and representations, which calculates symmetry-adapted functions used for the description of various ordered structures in crystals. It is assumed that the ordered structure, which is formed by a configuration of occupational probabilities, ion displacements, magnetic moments, q...
Antiferroquadrupolar (AFQ) and antiferromagnetic (AFM) order in DyB2 C2 have been investigated by theoretical symmetry analysis and neutron single crystal diffraction experiment with 0 to 4 T applied magnetic field along [100]. New symmetry arguments indicate that the AFQ ordering below TQ =24.7 K is accompanied by structural distortions involving...
Neutron diffraction data show that PrMn0.5Sn1.83 has a defect CeNiSi2-type crystal structure and orders antiferromagnetically below TN=16 K. The Pr magnetic moments are coupled antiferromagnetically according to the τ6 mode.
Neutron diffraction studies of polycrystalline R3Cu4Sn4 (R = Tb, Dy, Ho, Er) intermetallic compounds with the orthorhombic Gd3Cu4Ge4-type crystal structure indicate the existence of different magnetic structures. Rare earth atoms occupy two non-equivalent 2d and 4e sublattices. The rare earth magnetic moments order at low temperatures. For R = Tb a...
The magnetic ordering of TbRhSn, crystallizing in the hexagonal ZrNiAl-type structure, has been investigated by high-resolution neutron diffractometry in the temperature range between 1.7 and 23.9K. Tb in TbRhSn has been found to order magnetically below 19K. Its magnetic structure corresponds to propagation vector k→=[12,0,12], and by a new group-...
Neutron diffraction studies of polycrystalline R3Mn4Sn4 (R = La, Pr, Nd) intermetallic compounds with the orthorhombic Gd3Cu4Ge4-type crystal structure indicate the existence of different magnetic structures. The magnetic structures were studied with the support of group theoretical considerations. For R = La a sine wave modulated structure describ...
The symmetry analysis method is extended to analysis of quadrupole
ordering in solid ortho-hydrogen.
Representation analysis of the neutron diffraction data of RFe4Al8 (R=La, Ce, Y, Lu and Tb) tetragonal compounds (I4/mmm) for the wave vectors ), and leads to a large variety of modulated structures and enables a systematic classification of the used models in the calculation of powder neutron diffraction patterns. All observed magnetic structures...
Single phase polycrystalline samples of the ternary indides Ce1.95Pd2+2xIn1-x (0.05 less than or equal to x less than or equal to 0.23) and Ce2+xPd1.85In1-x (0.06 less than or equal to x less than or equal to 0.37) were synthesized and characterized by microprobe analysis and x-ray diffraction. The effect of the chemical composition on the magnetic...
The magnetic ordering of the novel binary compound ( structure type, space group Cmcm) has been studied by neutron diffraction, specific heat and magnetic measurements. Antiferromagnetic ordering of sets in below K and is associated with two wave vectors and .
The major magnetic phase with has a planar canted antiferromagnetic structure. Group the...
Neutron diffraction measurements for two HoPdSb samples obtained by two different ways of preparation (samples 1 and 2) are presented. Neutron data above TN (Néel temperature) indicate that HoPdSb exists in two different crystalline phases: cubic MgAgAs-type (F43m space group) and hexagonal LiGeGa-type (P63mc space group). The weight percentages of...
Neutron diffraction studies of polycrystalline (R=Tb, Dy, and Ho) intermetallic compounds with the orthorhombic -type crystal structure indicate different magnetic structures. For R = Tb, below , a collinear antiferromagnetic structure with a magnetic unit cell equal to the crystal one is observed. In the temperature region between and , it becomes...
Results of X-ray, neutron diffraction and magnetic measurements for RNiSb2 (RPr, Nd and Tb) compounds are presented. All compounds crystallize in the tetragonal CaBe2Ge2-type crystal structure and are antiferromagnets with the Néel temperature 6.3 K for R = Pr, 2.3 K for R = Nd and 12 K for R = Tb. Below TN a colinear antiferromagnetic structure o...
RNiSb2 (R = Pr, Nd and Tb) compounds crystallize in the tetragonal CaBe2Ge2 type crystal structure and are antiferromagnets with the Néel temperature 6.3 K for R = Pr, 2.3 K for R = Nd and 12 K for R = Tb. Below TN a collinear antiferromagnetic structure of the AFI type is observed for R = Nd, a square modulated structure with the wavevector k = (0...
In this work a proposal for a magnetic database and its presentation by computer program is given. The source files are organized in a way strictly adhering to CIF standard, accepted by International Union of Crystallography. These files contain information about the paramagnetic phase above the magnetic phase transition, and the magnetically order...
RNiSb2 (R = Pr, Nd and Tb) compounds crystallize in the tetragonal CaBe2Ge2 type crystal structure and are antiferromagnets with the Néel temperature 6.3 K for R = Pr, 2.3 K for R = Nd and 12 K for R = Tb. Below TN a collinear antiferromagnetic structure of the AFI type is observed for R = Nd, a square modulated structure with the wavevector k = (0...
The F2Pmp derivatives were prepared in 80–90% yield from commercially available protected l-4-iodophenylalanine by esterification with diazomethane followed by a CuCl-mediated coupling to (diethylphosphonyl) difluoromethylcadmium bromide. Moreover, treatment of l-4-iodoPhe-containing peptides under the same coupling conditions provided the F2Pmp-co...
Magnetic and structural properties of orthorhombic CeRhGe and NdRhGe (TiNiSi-type crystal structure) were studied by magnetometric and neutron diffraction methods. Both title compounds order antiferromagnetically below 10 K and 14 K respectively. The magnetic structure of the CeRhGe compound is collinear (C mode), whereas that of NdRhGe is describe...
Neutron diffraction study of polycrystalline UPd2Ge2 compound with the tetragonal body centered ThCr2Si2-type crystal structure shows successive modulated magnetic phases below TN ⋍ 135 K. For T ≤ 80 K, the propagation wave-vector k is locked to the commensurate value k=(0,0,kz=34); for T > 80 K kz becomes incommensurate varying with temperature fr...
Results of X-ray, neutron diffraction, Mössbauer effect and magnetometric measurements for RNi2Ge2 (R = Dy, Ho and Er) and YbNi2Si2 compounds are presented. All compounds crystallize in the tetragonal ThCr2Si2 (CeAl2Ga2)-type crystal structure and are antiferromagnets with the Néel temperature of 7.5 K for R = Dy, 4.8 K for R = Ho and 3.65 K for R...
The results of the neutron and X-ray diffraction and magnetometric measurements of TbCoSn and HoCoSn compounds are reported. Both compounds crystallize in an orthorhombic TiNiSi-type structure with the space group Pnma. The magnetometric measurements indicate the Néel temperatures at TN = 20.5 K for TbCoSn and TN = 8 K for HoCoSn. For TbCoSn below...
ErPdSn compound is antiferromagnetic with TN = 5.2 K. Below Tt = 2.5 K a square modulated structure with wave vector k = (13, 12, 13) exists. Above Tt it changes to a sine modulated structure with wave vector k = (kx, 12, kz). The Er3+ magnetic moment is 9.0(1)μB at T = 1.5 K and forms an angle of 75° with the c-axis and 80° with the a-axis. At T =...
HoNiGe and ErNiGe crystallize in an orthorhombic TiNiSi-type structure with the space group Pnma. Neutron diffraction measurements at low temperatures indicate magnetic structures with the wavevectors k1=[1/2,0,1/2] for HoNiGe and k2=[0,1/2,0] for ErNiGe. With an increase in temperature, a change in the magnetic structure to a modulated one with th...
The compound TbPdSn, with orthorhombic symmetry and TiNiSi-type structure, space group Pnma (D162h), orders antiferromagnetically at TN = (19+/-1) K. It orders at TN with a sine-wave-modulated magnetic spin arrangement with wavevector k = (0, 0.25, 0). Below TS = 10 K the low-temperature magnetic structure is characterized by propagation vector k =...
ErCoSi2 crystallizes in the orthorhombic CeNiSi2-type structure with the Cmcm space group and orders antiferromagnetically near TN = 2.6 K. The magnetic structure is incommensurate with a wavevector k = (0.467, 0, 0.5). The magnetic moment is in the a-c plane. The temperature dependence of lattice constants indicates a positive exchange striction....
The results of X-ray neutron diffraction and magnetometric measurements for TbNiGe and DyNiGe compounds are presented. Both compounds crystallize in an orthorhombic TiNiSi-type crystal structure and are antiferromagnets with Néel temperature of 18 and 6 K, respectively. At low temperatures both compounds have square modulated structures with a wave...
Neutron diffraction study of beta-NaFe0.25Al0.75O2 indicates that the sample has the crystal structure corresponding to that of beta-NaFeO2. The Fe and Al atoms occupy randomly the same kind of crystallographic sites. Below TN = 1.65 K a collinear antiferromagnetic order with the magnetic unit cell doubled along the a-axis is present.
The calculation of the spin wave spectrum by the symmetry analysis method is given in this work. The symmetry calculations are based on the P-type colour group as the symmetry group of magnetic structure. It is consistent with the exchange approximation of the spin wave Hamiltonian. The method is applied to the spin wave spectrum calculation for he...
The symmetry analysis of possible magnetic structure models in hexagonal manganites LMnO3, starting with the choice of D46h 1˙' group as the symmetry group of the initial paramagnetic phase, is given in this work. The two, two-dimensional irreducible representations (IR-s) describing the xy triangular magnetic structure models are calculated. I...
The relation between the results of symmetric and combinatorial analysis of ordering transitions is presented. The combinatorial method gives the possibility of finding interstitial structures with minimal energy at T = 0 K. The symmetric method gives the sequence of phase transitions from initial to final structure. The final structure at T = 0 K...
Order-disorder phase transitions for the Me-X structures in Nb-H(D) hydrides with hydrogen (deuterium) ordering over the 12d tetrahedral interstices of the Γvc lattice and for the Me-X and Me-X2 oxides in the Ta-O system with oxygen ordering over octahedral 6b interstices are presented. The concentration of interstitial atoms is assumed to be const...
The results of neutron diffraction measurements performed on CeDx near the trihydride composition MeD3 at room temperature and on LaD2.9 at liquid nitrogen and room temperatures are presented. Superstructure reflections have been found. The system of additional reflections in lanthanum deuteride is different from that in cerium deuteride. The conce...
The symmetry analysis method based on the theory of group representations is used for description of complex systems and their
behavior in this work. The first trial of using the symmetry analysis in modeling of behavior of complex social system is
presented. The evacuation of large building scenarios are discussed as transition from chaotic to ord...
