Time filter

Source Type

Nowak B.,Institute of Low Temperature And Structure Research
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We present the results of nuclear magnetic resonance (NMR) studies on CePt4In crystallizing at ambient temperature in an ordered cubic MgCu4Sn-type structure (space group F-43m, no. 216). The In115 and Pt195 NMR powder spectra have provided microscopic evidence for the occurrence of the phase transition suggested by the specific heat anomaly at T 0=205 K. Single-site (multiple-site) Pt195 (I=1/2) NMR spectra are observed above (below) T0, while the single-site In115 (I = 9/2) NMR signal disappears below T0. The Solomon echoes of half-integer quadrupolar nuclei with spin I = 9/2 have been observed. The Knight shifts 115Kiso(T) and 195Kα(T) (α = //, , iso, ax) scale linearly with magnetic susceptibility χ(T). Pt195 NMR exhibits strong anisotropy of the Knight shift and nuclear spin-lattice relaxation rate due to the huge anisotropy of hyperfine fields (H///H) 43. The (1/T 1)iso are fast and temperature independent for both In115 and Pt195 nuclei, indicating that the spin fluctuation of the 4f electrons has a local nature at the Ce sites. © 2011 American Physical Society.


Crystal structures of two polymorphs of [H2m4na]Cl (1α,1β) and (H2m4na)2SnCl6·H2O (2), where 2m4na = 2-methyl-4-nitroaniline are shown and comparison of these crystal structures with the bromide salt reported earlier is presented. In all the presented crystal structures, alternatively arranged cations and anions form chain and ring hydrogen-bonding patterns of weak unconventional N-H⋯Cl hydrogen bonds. Interrelations among the elementary graph-set descriptors and descriptors of the hydrogen-bonding patterns are presented. Nonhydrogen bonding interactions between the nitro groups are also described using graph-set descriptors. Comparison of the experimental, also for deuterated 1α polymorph, and theoretical, for H2m4na+ ion with B3LYP/6-31G(d,p), spectra showed good agreement among the frequencies due to very weak interactions existing in studied compounds. Detailed analysis of the spectra revealed that the interaction between adjacent -NO2 groups in 1α is stronger than the other types involving the nitro group. The bands were assigned on the basis of theoretical calculations of vibrational frequencies for H2m4na+ ion and PED analysis. © 2013 American Chemical Society.


Maczka M.,Institute of Low Temperature And Structure Research
Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2012

A high-pressure Raman scattering study of wolframite-type Mn(0.97)Fe(0.03)WO(4) is presented up to 10.4 GPa. The phonon wavenumbers vary linearly with pressure. The mode Grüneisen parameters are larger for many bending and lattice modes when compared to the stretching modes due to the larger compressibility of Mn(Fe)O(6) octahedra when compared to WO(6) octahedra. Combining the pressure-dependent Raman data of this work with the temperature-dependent Raman data on this crystal previously reported by us has allowed estimation of the temperature-dependent pure lattice and intrinsic anharmonic contributions to the observed total Raman shifts as a function of temperature. It has been found that the observed unusual hardening of the 884, 698 and 674 cm(-1) stretching modes upon heating from 4 to about 150-200 K followed by the usual softening above 150-200 K is a result of a positive intrinsic anharmonic contribution and a negative pure lattice contribution; i.e., up to about 150-200 K the anharmonic contribution surpasses the lattice contribution and the total Raman shift is slightly positive whereas above 150-200 K the lattice contribution becomes dominant and the Raman bands exhibit the usual softening with increasing temperature.


Daszkiewicz M.,Institute of Low Temperature And Structure Research
CrystEngComm | Year: 2013

Perpendicular arrangement of two nitro groups of adjacent molecules was found in 104 structural fragments deposited in the Cambridge Structural Database. In the most cases, this non-hydrogen bonding O NO2⋯π(N)NO2 interaction is shorter than 3 Å. Ab initio calculations of the interaction energy indicates the attractive nature of this interaction, comparable to the Eint of C-H⋯O. © 2013 The Royal Society of Chemistry.


Daszkiewicz M.,Institute of Low Temperature And Structure Research
Journal of Molecular Structure | Year: 2013

New hybrid organic-inorganic compound, bis(1,4-H2-1,2,4- triazolium) hexachloridostannate(IV) monohydrate, [(1,4H2t) 2SnCl6]ṡH2O crystallizes in P2 1/c space group. Weak hydrogen bonds exist in the structure. The route of protonation of the 1,2,4-triazole and tautomer equilibrium constants for the cationic forms were theoretically studied by means of B3LYP/6-31G · method. The 1,4H2t+ cation turned out to be the most stable form of mono-protonated species. Calculated IR and Raman spectra for 1,4H2t+ cation (gas phase) are in very good agreement with the experimental data. Infrared and Raman bands were assigned on the basis of PED analysis. © 2012 Elsevier B.V. All rights reserved.


Kontrym-Sznajd G.,Institute of Low Temperature And Structure Research
Journal of Applied Crystallography | Year: 2015

This paper complements two previous papers devoted to Special directions in momentum space. I. Cubic and II. Hexagonal, tetragonal and trigonal symmetries [Kontrym-Sznajd & Samsel-Czekala (2011). J. Appl. Cryst. 44, 1246-1254; Kontrym-Sznajd & Samsel-Czekala (2012). J. Appl. Cryst. 45, 1254-1260], in which sets of special directions (SDs) were proposed. Such directions, employing the full symmetry of the Brillouin zone, allow for constructing in the whole space anisotropic quantities from their known values along a few directions. SDs also define which spectra, measured in, for example, Compton scattering experiments, are the most efficient for reconstructing three-dimensional densities from their one-dimensional projections. This paper, in which new sets of special directions (SDs) for cubic structures are proposed, is devoted mainly to practical applications of SDs. Taking into account experimental uncertainty, an optimal strategy for experimental investigations is discussed. © 2015 International Union of Crystallography.


Janczak J.,Institute of Low Temperature And Structure Research
Crystal Growth and Design | Year: 2015

A family of supramolecular complexes of 1-(diaminomethylene)thiourea with aliphatic dicarboxylic acids, HOOC(CH2)nCOOH, with odd and even numbers of methylene groups in the carbon chain of the acids has been characterized. Using solvent-assisted and evaporation-based techniques, crystallization of 1-(diaminomethylene)thiourea with aliphatic dicarboxylic acids from water solutions yielded ionic supramolecular complexes with base to acid ratio of 2:1 or 1:1. Malonic, succinic, adipic, and sebacic acids with 1-(diaminomethylene)thiourea form supramolecular complexes of 2:1 ratio (1, 2, 4, and 8), whereas glutaric, pimelic, azelaic, and suberic acids form supramolecular complexes of 1:1 ratio (3, 5, 6, and 7). Within all supramolecular complexes only one with adipic acid crystallizes as a hydrate containing water molecules of crystallization. In the hydrated crystal with adipic acid, the O-H···O chains of water molecules interact with adipiate(2-) anions forming anionic layers, and the charge is compensated by 1-(diaminomethylene)thiouron-1-ium cations. The 2:1 supramolecular complexes further interact each other via N-H···O hydrogen bonds forming two- or three-dimensional supramolecular structure. Within 1:1 supramolecular complexes, the singly deprotonated aliphatic dicarboxylic acids are linked together via strong symmetrical O···H···O hydrogen bonds into infinitive chains. The chains are further linked by 1-(diaminomethylene)thiouron-1-ium cations to form a two- or three-dimensional hydrogen bonding network. Interaction between the 1-(diaminomethylene)thiouron-1-ium and the singly or doubly deprotonated aliphatic dicarboxylic acid units in solid of 1-8 supramolecular complexes were also analyzed by vibrational spectroscopy. © 2015 American Chemical Society.


Zaleski T.A.,Institute of Low Temperature And Structure Research
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

The excitations of strongly interacting bosons confined in a two-dimensional square lattice are studied. Using a combined Bogoliubov method and the quantum-rotor approach, the Hamiltonian of strongly interacting bosons is mapped onto the U(1)-phase action. This allows to calculate the momentum- and energy-resolved one-particle spectral function and its dependence on the presence of the superfluid phase. It is shown that the destruction of the ordered phase leads to the opening of the gap in the excitation spectrum in k=0. On the other hand, superfluidity manifests itself as a sharp coherence peak resulting from the emergence of the long-range order. Correlation effects lead to the appearance of a smearing of the band structure of incoherent particles although the remnants of the Bogoliubov excitations are still present in the coherent part of the spectrum. © 2012 American Physical Society.


Okal J.,Institute of Low Temperature And Structure Research
Catalysis Communications | Year: 2010

Ru/γ-Al2O3 catalyst of 1.1% was prepared by reduction of RuCl3 in ethylene glycol using a microwave-assisted solvothermal method. Structure of the as-prepared and heated in H2 at 500-700 °C catalyst samples was studied by XPS, BET, XRD and HRTEM techniques. The catalyst dispersion was determined by various chemisorption techniques and agreement between them was reasonable. The dispersion of fresh catalyst decreased slightly from 0.53 to 0.49 by hydrogen treatment at 700 °C, and good correspondence with HRTEM data was obtained. Results indicate on high stability of the Ru nanoparticles in the low-loaded colloidal Ru/γ-Al2O3 catalyst under reducing conditions. © 2009 Elsevier B.V. All rights reserved.


Daszkiewicz M.,Institute of Low Temperature And Structure Research
Structural Chemistry | Year: 2012

The hydrogen bonding patterns can be described on the basis of the graph-set approach. Since a set of individual hydrogen bonds create the hydrogen bonding pattern, these individuals can be described independently by the graph-set descriptors. The descriptors can be added to each other resulting in a descriptor of the pattern. Algebraic equations based on the graph-set descriptors are given. Alternatively, the hydrogen bonding pattern can be considered as an ordered molecular assembly. Therefore, the proper elementary graph-set descriptor, Ed a(n), associated with the molecules can be utilized to obtain a descriptor of hydrogen bonding patterns. The procedure of the appropriate graph-set summation, leading to the complex pattern, is described. © The Author(s) 2011.

Loading Institute of Low Temperature And Structure Research collaborators
Loading Institute of Low Temperature And Structure Research collaborators