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The atomic structure of the family of ferecrystals [(SnSe)1.15]m(TaSe2) (m = 1, 3, and 6) was investigated by means of transmission electron microscopy. The tantalum in the TaSe2 layers was observed to have trigonal prismatic coordination similar to that found in the 2H polytype of bulk TaSe2. The structure of the SnSe constituent was found to be similar to that of orthorhombic α-SnSe. In the compounds with m = 1 and m = 3, regions with a local ordering of the layers along a commensurate axis, similar to the ordering in conventional misfit layer compounds, were observed. However, on a longer range the ferecrystals were found to exhibit a turbostratically disordered structure. Stacking defects were occasionally found in the samples in which a layer is interrupted and the surrounding layers are bent around these defects, while maintaining abrupt interfaces instead of interdiffusing. Volume defects were found in one sample of [(SnSe)1.15]1(TaSe2)1 in which a SnSe layer locally substitutes a part of a TaSe2 layer without interrupting the surrounding layers.

The turbostratically disordered misfit layer compound (SnSe) 1.15 VSe 2 was synthesized and structurally characterized. Electrical transport measurements suggest this compound undergoes a charge or spin density wave (CDW or SDW) transition, which has not been observed in previous misfit layer compounds. The (SnSe) 1.15 VSe 2 compound, created through the modulated elemental reactants technique, contains highly oriented intergrowths of SnSe bilayers and VSe 2 structured Se–V–Se trilayers with abrupt interfaces between them perpendicular to the c -axis. X-ray diffraction data and transmission electron microscope images show that each constituent has in-plane crystallinity but that there is a random rotational disorder between the constituent layers. Temperature-dependent electrical resistivity data and Hall measurements are consistent with (SnSe) 1.15 VSe 2 being a metal, however an abrupt increase in the resistivity occurs between 30 and 100 K. The carrier concentration decreases by approximately 1 carrier per vanadium atom during this temperature interval.

Several new metastable layered intergrowths based on tin monoselenide and molybdenum diselenide, [(SnSe)1+δ]m[MoSe2]n, have been prepared by self-assembly from elemental nanolaminate precursors deposited by physical vapor deposition. The thin-film specimens were characterized by laboratory x-ray reflectivity and diffraction, synchrotron x-ray diffraction, electron probe microanalysis, and scanning transmission electron microscopy techniques, all of which indicate the formation of intergrowths with precise layering and well-defined composition. Analysis of in-plane diffraction originating from the individual components yields a structural misfit of δ = 0.06 and suggests turbostratic misorientation of the individual layers. In contrast to most known [(MX)1+δ]m[TX2]n-type chalcogenide compounds, electrical transport data for the [(SnSe)1+δ]1[MoSe2]1 composition are consistent with semiconducting behavior.

Thin Ni/Al and Ni/Ga layers of different atomic ratios were codeposited onto Si(001) at room temperature followed by subsequent annealing. Influence of annealing temperature on morphology and composition of ternary disilicide NiSi2-xAlx and NiSi2-xGax layers was investigated by transmission electron microscopy. Addition of Al or Ga leads to a decrease of the disilicide formation temperature from 700°C down to at least 500°C. Depending on the composition closed, uniformly oriented NiSi2-xAlx and NiSi2-xGax layers were observed after annealing at 900°C, whereas reaction of a pure Ni film with Si leads to the island formation with a mixture of A- and B-type orientations.

We review our results on the growth of ZnTe- and CdTe-based nanowires (NWs) and on their basic structural and optical properties. The nanowires were produced by using molecular beam epitaxy (MBE) with the use of a mechanism of catalytically-enhanced growth. The growth of ZnTe, CdTe, ZnMgTe and ZnMnTe nanowires was performed from elemental Zn, Cd, Mn, Mg and Te sources on the surfaces of (001)-, (110)- and (111)B-oriented GaAs substrates with Au nanocatalysts. The morphological and structural properties of the nanowires were assessed by using X-ray diractometry, field-emission scanning electron microscopy, and high resolution transmission electron microscopy. Additional studies of the compositions of both the nanowires and the Au-rich nanocatalysts were performed with the use of energy dispersive X-ray spectroscopy. The optical properties of the NWs were assessed by using photoluminescence and Raman-scattering studies performed in both macro and micro modes. The studies revealed that binary and quaternary nanowires with average diameters from 30 to 70 nm and lengths from 1 to 2.6 µm were monocrystalline in their upper parts, their growth axis was h111i, and they grow along the [111] direction of the substrate, independent of the substrate orientation used. A Au-rich (with 20 % Ga) spherical nanocatalyst was always visible at the tip of a nanowire, thus indicating that a vapor-liquid-solid mechanism was responsible for the growth of the ZnTe- and the CdTe-based nanowires. The formation of homogeneous mixed crystal ZnMnTe and ZnMgTe nanowires was demonstrated by measurements of the variation of the lattice constant and by Raman experiments that revealed the expected shift and appearance of new phonon lines and a strong enhancement of the LO-phonon structures for an excitation close to the exciton energy of the NW materials. The photoluminescence from the internal Mn 2+ transition between crystal-field-split energy levels ( 4 T1 ! 6 A1) was observed in the ZnMnTe nanowires.

High surface area (HS) metal fluoride supported palladium catalysts (Pd0/MFx) (MFx = AlF3, MgF2, CaF2 and KMgF3) together with the respective Pd-free HS-MFx catalysts have been prepared via a novel sol–gel synthesis. In a first step, the reaction of anhydrous hydrogen fluoride (aHF) with the respective solutions of the metal alkoxides containing up to 10% Pd(acac)2 yielded the catalyst precursors as HS-gels. In a second step, gas phase fluorination followed by H2-treatment was employed to obtain the final Pd0/MFx catalysts. X-ray diffraction (XRD) indicated the formation of mainly amorphous AlF3 and Pd0/AlF3, whereas bulk MgF2, CaF2 and KMgF3 and the respective Pd-loaded phases were partially crystalline. The XRD patterns of Pd0/MFx revealed besides the occurrence of broad MFx-reflections only very weak reflections for Pd0 supporting a uniform dispersion of Pd nanoparticles inside the highly distorted MFx structures as it was independently reconfirmed by TEM-investigations. FTIR photo-acoustic spectroscopy with pyridine chemisorption (FTIR-PAS) and dismutation activities showed that AlF3 and MgF2 bulk as well as the supported Pd samples possess strong to moderate Lewis acidities. CaF2 and KMgF3 bulk as well as the respective Pd samples were found to be neutral. BET specific surface areas of MFx and Pd0/MFx are very high, up to ten times higher than known from literature. TEM showed homogeneously dispersed Pd nanoparticles on MFx matrices with a mean particle size of ∼5 to 8 nm. Catalytic activities of the samples were tested for the conversion of CHClF2 into valuable compounds by gas phase dismutation, hydrodehalogenation and pyrolysis, in presence as well as absence of hydrogen. Based on the obtained results and D/H-isotope exchange measurements, a carbene mechanism involving competitive dismutation coupled with consecutive reactions is proposed for the hydrodehalogenation process.

The relationship between microstructure and magnetic properties of a (Fe,Co)NbB-based nanocrystalline soft magnetic alloy was investigated by analytical transmission electron microscopy (TEM). The microstructures of (Fe0.5Co0.5)80Nb4B13Ge2Cu1 nanocrystalline alloys annealed at different temperatures were characterized by TEM and electron diffraction. The magnetic structures were analyzed by Lorentz microscopy and off-axis electron holography, including quantitative measurement of domain wall width, induction, and in situ magnetic domain imaging. The results indicate that the magnetic domain structure and particularly the dynamical magnetization behavior of the alloys strongly depend on the microstructure of the nanocrystalline alloys. Smaller grain size and random orientation of the fine particles decrease the magneto-crystalline anisotropy and suggests better soft magnetic properties which may be explained by the anisotropy model of Herzer.

The potential of combined use of conventional transmission electron microscopy (CTEM), high-resolution TEM imaging (HRTEM) and digital analysis is applied to study (Si,Ge) islands grown by liquid phase epitaxy (LPE) on Si substrates and Ga(Sb,As) quantum dot (QDs) structures grown by metal-organic chemical vapour deposition (MOCVD) on GaAs substrates. The classical diffraction contrast method is applied to visualize the strain field in the surrounding of the QDs. Dark-field imaging allows a qualitative imaging of chemical composition using chemically sensitive reflections. Furthermore, it will be presented how the techniques of quantitative HRTEM (qHRTEM) can be used to determine the local strain and structural peculiarities on atomic scale.

Sr 2 TiSi 2 O 8 single crystals were grown by Czochralski pulling and from a high-temperature solution. X-ray diffractometry revealed the modulated crystal structure of Sr 2 TiSi 2 O 8 to belong to the 5D superspace group P 4 bm (− α , α , 1/2; α , α , 1/2) with α =0.3. Atomic positions, anisotropic displacement factors and positional modulation parameters for Sr 2 TiSi 2 O 8 are determined and discussed. The positional modulation is further investigated by electron diffraction and high-resolution transmission electron microscopy. In the latter experiments, the 2D modulation appears to be superimposed by some 1D modulation waves. This effect is discussed in terms of growth conditions.

The structure of the off-stoichiometric In-rich ternary phase CuIn 5 Se 8 was studied by means of electron diffraction and high-resolution electron microscopy. The compound shows a layered structure with a 7-layer stacking sequence of closed-packed planes, which contains both cubic and hexagonal stacking of Se atoms. The studied CuIn 5 Se x bulk crystal is known as the β-phase of this compound.

We describe an implementation of a general standard basis algorithm, valid for any monomial ordering compatible with the natural semigroup structure. We concentrate on new strategies which have proved useful, in particular in the non-wellordering case. Moreover, we describe the first implementation of Schreyer's method to compute syzygies and compare it with other, more classical methods. Comparisons of the computing time of several examples in the system SINGULAR give hints as to which strategies should be used in different classes of examples.

Internal interfaces in solids influence and/or even control essential properties of materials. In order to have a thorough understanding of structure-property correlations, systematical investigations of the atomic stucture of interfaces and boundaries are necessary. The atomic stucture of interfaces and boundaries can be determined by high-resolution electron microscopy (HREM). The different techniques of analytical electron microscopy (energy-dispersive X-ray spectroscopy — EDX, electron energy loss spectroscopy — EELS, and convergent beam electron diffraction — CBED) provide the required information on the chemical composition of the interface regions. In order to determine the equilibrium stucture and the energy of an interface, atomistic simulations of the interface stucture have to be carried out. The relaxed interface stucture may be simulated applying molecular dynamical (MD) calculations and the methods of static energy minimization (MS). For all interface calculations a suitable geometrical model has to be generated (construction of the computational cell). Then, the interatomic interaction process as well as the relaxation process have to be taken into consideration. In the following various crystallographic concepts of characterizing interface stuctures are treated. In general, the determination of the symmetry of the two adjacent crystals and of that of the interfaces between them is very important both for the analysis and the prediction of possible interface structures. A useful classification scheme for crystalline interfaces is to distinguish between homophaseand heterophase boundaries, sometimes also denoted as grain boundaries and interphase boundaries, respectively. Homophase boundaries are interfaces between two crystals with the same crystal structure and the same chemical composition. Grain boundaries and other

The nanostructure of ferecrystals [(SnSe) 1+δ ] m [TSe 2 ] n with T = Mo, Ta, synthesized by the modulated elemental reactants (MER) method with 1 ≤ m, n ≤ 30, was investigated by various methods of transmission and scanning transmission electron microscopy (TEM/STEM), including precession electron diffraction (PED). The influence of the layer composition, sequence, and thickness, on the resulting intergrowth structure and disorder is elucidated, including various aspects of intra- and inter-layer stacking disorder.

The basics of precession electron diffraction (PED) in a transmission electron microscope (TEM) are briefly discussed. An automated system for the mapping of nanocrystal phases and orientations in a TEM is briefly described. This system is primarily based on the projected reciprocal lattice geometry as extracted from experimental precession electron diffraction spot patterns. Comprehensive open-access crystallographic databases may be used in support of the automated crystallite phase identification process and are, therefore, also briefly mentioned.

Ordering of Cu and In atoms in near-stoichiometric CuInS2 epitaxial films grown on Si (111) by molecular beam epitaxy was studied by transmission electron microscopy. Nonchalcopyrite ordering of the metal atoms in CuInS2 is observed, which is identified as CuAu-type ordering. Sharp spots in electron diffraction patterns reveal the ordered Cu and In atom planes alternating along the [001] direction over a long range. High-resolution electron microscopy confirms this ordering. The CuAu-ordered structure coexists with the chalcopyrite ordered structure, in agreement with theoretical prediction.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007

Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007

Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007

The single crystal growth of GaAs for epitaxial substrates is inseparably correlated with the formation of As precipitates of some nanometers in diameter due to retrograde solubility during cooling of the crystal to room temperature. These precipitates are the origin of diffuse scattering observed as weak lines in transmission electron diffraction (TED) pattern (see Fig. (A)). In order to thoroughly understand the structural characteristics of the precipitates computer simulations of the TED patterns were performed. Simulations were carried out via two different approaches. In a first simplified assumption 2-dimensional projections of the structure along [111] and [110] were considered. For the evaluation of the agreement between structure model and experimental findings the Fourier transform of the projected positions of the atoms was calculated. The regular positions of the atoms of the sphalerite structure are depicted as grey dots in Fig. (B). The Fourier spectrum clearly exhibits intensity maxima at positions expected for the perfect crystal (see Fig. (C)). In order to generate the diffuse lines in the Fourier spectrum interstitial atoms have to be incorporated. With respect to the ratio of its ionic radii, Ga and As are preferentially incorporated on a 4-fold coordinated site. But, an agreement is found only for the arrangement of interstitials as given in Fig. (B) as black dots. These positions are either the 3-fold or 2-fold coordinated ones which are not distinguishable in this projection. For visualization of the two-dimensional arrangement, the interstitial atoms were connected by lines not contributing to the Fourier spectrum. In addition to this first approach, simulations of the TEDpattern basing on three-dimensional models structurally relaxed by molecular dynamics calculations will be discussed. The findings of the computer simulations will be verified by comparison with results of high-resolution transmission electron microscopy (HRTEM) as well as high-angle annular dark-field scanning TEM (HAADF STEM).

The beginning of a new year is traditionally a time for both looking back on the highlights of the previous year and for getting ready to start into the year to come. The last year was remarkable with respect to two events. First, our journal celebrated its 40th anniversary. The journal was founded as “Kristall und Technik ” by Professors Will Kleber and Hermann Neels in 1966. The content of the first issue of “Kristall und Technik” (subtitle: Zeitschrift fur experimentelle und technische Kristallographie) consisted of 19 original papers, where 18 of them were written in German and 1 in Russian, and 1 short note. Nowadays, “Crystal Research and Technology” is a fully international journal where all contributions are published in English. Moreover, papers ever published in “Crystal Research and Technology” are now available online. Second, the crystallographic community celebrated the 100th anniversary of Will Kleber, one of the founders of Crystal Research and Technology. This event was appreciated by a colloquium on December 15, 2006. A brief report about its topics will be given in a forthcoming issue. The highlight of the year 2007 is certainly the 200th anniversary of the foundation of the Wiley Publishing House and its successful service to a broad scientific community. The motto of Wiley “1807 – 2007 Knowledge for Generations” is also guideline for our engagement in the broad field of theoretical and experimental crystallography. The readers can be sure that we will strive to serve best the crystallographic community in this sense. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The influence of the crystal shape on the fine structure of transmission electron diffraction (TED) patterns described by the crystal shape amplitude is discussed. A general algebraic expression for the crystal shape amplitude of any crystal polyhedron is used for computing the intensity distribution of TED reflections. The computer simulation method is applied to the analysis of the fine structure of TED patterns of small gold and palladium crystals having octahedral and tetrahedral habits.

Summary In stroke-prone spontaneously hypertensive rats, oral long-term treatment with verapamil, propranolol, hydrochlorothiazide, and dihydralazine attenuated the development of hypertension. The various antihypertensive drugs caused comparable reductions in blood pressure but the calcium antagonist and the β-receptor blocker prolonged the life span more than the diuretic and vasodilator. The relative heart and lung weights at the time of death were slightly diminished in the verapamil and the high-dose propranolol group. It is assumed that calcium antagonism and β-receptor blockade prolong the life span, not only due to their blood-pressure-lowering mechanism, but also to the additional protective effects.

36th International School on the Physics of Semiconducting Compounds, Jaszowiec, POLAND, JUN 09-15, 2007; International audience; Catalytically enhanced growth of ZnMnTe diluted magnetic semiconductor nanowires by molecular beam epitaxy is reported. The growth is based on the vapor-liquid-solid mechanism and was performed on (001) and (011)-oriented GaAs substrates from elemental sources. X-ray diffractometry, scanning and transmission electron microscopy, atomic force microscopy, photoluminescence spectroscopy, and Raman scattering were performed to determine the structure of nanowires, their chemical composition, and morphology. These studies revealed that the obtained ZnMnTe nanowires possess zinc-blende structure, have an average diameter of about 30 nm, typical length between 1 and 2 mu m and that Mn2+ ions were incorporated into substitutional sites of the ZnTe crystal lattice.