Atomic Splitting Research Articles

Theoretical insights into the interplay between metal-organic and covalent bonding in single-layer molecular networks formed by halogen dissociation.

Synthesis via dehalogenative coupling due to thermal annealing is one of the most common routes of growing metal-organic and covalent polymer networks on catalytic metal surfaces. We present a computational approach taking into account both metal-coordinated and covalent C-C bonding interactions, which drive the self-assembly of tetrabrominated polyarene molecules into single-layer ordered and disordered nanostructures. The proposed coarse-grained lattice model is simulated using the Monte Carlo method. We investigate the annealing effect in ensembles of nearly and fully dehalogenated molecules, accordingly decreasing the concentration of dissociated (chemisorbed) halogen atoms, to account for the desorption process. The results suggest that dissociated halogens may be at least partially responsible for fragmentation of metal-organic networks on the Cu and Au surfaces. The simulations also show that fragmented covalent networks are mostly disordered or characterized by short-range glass-like order, but larger domains of these phases can be obtained after removing the split off Br atoms. We additionally examine the potential formation of fragments with a hybrid structure consisting of oligomer chains linked side-to-side by metal adatoms.

Re-Co alloys and single-atom Re catalysts in ammonia synthesis: A DFT study

• BE of the N atom adsorbed on Co, Re, Re 3 Co 1 is -5.61, -6.71, -7.05 eV, respectively. • Re-Co alloys exhibit a variable synergy depending on the rate-determining step. • Re centers on Co split nitrogen atoms in electronic and thermodynamic properties. • Weakly bound N atoms work well on a surface modified by strongly bound N atoms. In this study, density functional theory calculations and microkinetic modeling were used to estimate the catalytic activity of Re δ Co 1-δ (0001) alloys (δ = 0; 0.25; 0.5; 0.75, 1), and Co(0001)-supported single- Re 1 and dual-atom Re 2 centers in the synthesis of ammonia. Nitrogen atoms (N ad ) form an ordered structure, and the bridge state is most active among others on the Re(0001) plane; while N ad are concentrated around the Re 1 and Re 2 centers, splitting in electronic and thermodynamic properties. The specific catalytic activity of the centers Re 1 , Re 2 and the Re(0001) plane changes in the order of 8.0·10 3 , 32.0, and 1.0, respectively, due to weakly bound but highly active N ad , which are stabilized by strongly bound and low-active N ad . The calculations revealed the NRe 3 state on the Re 3 Co 1 alloy with an abnormally high binding energy (BE) of -7.05 eV, unequal Re-N distances and Re5d fillings, in contrast to the similar NRe 3 state on Re(0001) with BE = -6.71 eV. A variable synergism of Re-Co alloys was established: the Re 3 Co 1 or Re 1 Co 3 alloy exhibits maximum catalytic activity if the rate-determining step is the formation or hydrogenation of N ad under appropriate experimental conditions, respectively.

Primary damage of 10 keV Ga PKA in bulk GaN material under different temperatures

Molecular dynamics (MD) simulations were conducted to investigate the temperature effects on the primary damage in gallium nitride (GaN) material. Five temperatures ranging from 300 K to 900 K were studied for 10 keV Ga primary knock-on atom (PKA) with inject direction of [0001]. The results of MD simulations showed that threshold displacement energy (Ed) was affected by temperatures and at higher temperature, it was larger. The evolutions of defects under various temperatures were similar. However, the higher temperature was found to increase the peak number, peak time, final time and recombination efficiency while decreasing the final number. With regard to clusters, isolated point defects and little clusters were common clusters and the fraction of point defects increased with temperature for vacancy clusters, whereas it did not appear in the interstitial clusters. Finally, at each temperature, the number of Ga interstitial atoms was larger than that of N and besides that, there were other different results of specific types of split interstitial atoms.

Hydrogen spillover through Matryoshka-type (ZIFs@)n\u22121ZIFs nanocubes

Hydrogen spillover phenomenon is well-documented in hydrogenation catalysis but still highly disputed in hydrogen storage. Until now, the existence of hydrogen spillover through metal–organic frameworks (MOFs) remains a topic of ongoing debate and how far the split hydrogen atoms diffuse in such materials is unknown. Herein we provide experimental evidence of the occurrence of hydrogen spillover in microporous MOFs at elevated temperatures, and the penetration depths of atomic hydrogen were measured quantitatively. We have made Matryoshka-type (ZIFs@)n−1ZIFs (where ZIFs = ZIF-8 or ZIF-67) nanocubes, together with Pt nanoparticles loaded on their external surfaces to produce atomic hydrogen. Within the (ZIFs@)n−1ZIFs, the ZIF-8 shell served as a ruler to measure the travelling distance of H atoms while the ZIF-67 core as a terminator of H atoms. In addition to the hydrogenolysis at normal pressure, CO2 hydrogenation can also trace the migration of H atoms over the ZIF-8 at high pressure.

Phase transitions to superionic Li2Te and Li2Se – A high-temperature neutron powder diffraction study, atom displacements, probability density functions and atom potentials

Despite much research on Li ion batteries at ambient temperature, Li-ion conductors at high temperature have received less attention. In the series of ionic Li2X compounds (X = O, S, Se, Te), superionic phase transitions have been reported for Li2O and Li2S. The lower transition temperature of Li2S, supposedly caused by the larger anion size of S, inspired the investigation of the superionic behavior of Li2Se and Li2Te. Their thermal expansion and thermally excited spatial distribution of Li cations and Se/Te anions was monitored by neutron diffraction up to 800 °C for Li2Te and up to 1000 °C for Li2Se. Both compounds exhibit positive thermal expansion with changing coefficient of expansivity at the superionic transition temperatures. No deviation from cubic metrics or abrupt changes of the cell volume were observed. Rietveld refinements of the fluorite-type structures (space group Fm3¯m) employing Gaussian spatial distribution functions reveal discontinuities in the slope of the increasing mean square displacement parameters as a function of temperature. At ~600 °C (Li2Te) and ~780 °C (Li2Se), the mean square displacements of Li atoms increase abruptly, indicating a superionic transition. For the Te/Se anions, similar discontinuities occur at slightly lower temperatures. Difference Fourier syntheses reveal strongly anisotropic Li spatial distribution density around the 8c (¼ ¼ ¼) positions of cubic site symmetry m3¯m. Moving the maximum of the density distribution to adjacent 32f (xxx) (site symmetry .3 m) positions introduces four virtual split atoms. In addition to the small displacement x along 〈111〉, denoting the mean positions of the split atoms, anisotropic spatial distributions may then be refined. Whereas x deviates from ¼ as an almost linear function of temperature, the abrupt changes in the increase of mean square amplitudes of thermal displacements with temperature are retained. Significantly improved profile refinement residuals support this flexible structure model. Temperature-dependent joint probability density function maps demonstrate the increasing delocalization of Li atoms and yield potential energy distributions, i.e. the energy barriers of ionic transport. The potential barrier between adjacent Li positions at the octahedral site at (½ ½ ½) shows an abrupt drop at the superionic phase transition temperature. The derivative of the potentials, i.e. the restoring forces of Li atom motions show clear deviations from linearity. The anharmonicity of thermally excited spatial atomic distribution refined using the Gram-Charlier series expansion with third- and fourth-order tensor components confirms the enhanced thermal motion in the high-temperature regime. The overall cubic crystal symmetry is maintained.

Pressure dependence of electron density distribution and d-p- π hybridization in titanate perovskite ferroelectrics

Electron density distributions of $\mathrm{PbTi}{\mathrm{O}}_{3}, \mathrm{BaTi}{\mathrm{O}}_{3}$, and $\mathrm{SrTi}{\mathrm{O}}_{3}$ were determined by synchrotron x-ray powder diffraction up to 55 GPa at 300 K and ab initio quantum chemical molecular orbital (MO) calculations, together with a combination of maximum entropy method calculations. The intensity profiles of Bragg peaks reveal split atoms in both ferroelectric $\mathrm{PbTi}{\mathrm{O}}_{3}$ and $\mathrm{BaTi}{\mathrm{O}}_{3}$, reflecting the two possible positions occupied by the Ti atom. The experimentally obtained atomic structure factor was used for the determination of the deformation in electron density and the d-p-$\ensuremath{\pi}$ hybridization between ${d}_{xz}$ (and ${d}_{yz}$) of Ti and ${p}_{x}$ (and ${p}_{y}$) of O in the Ti-O bond. Ab initio MO calculations proved the change of the molecular orbital coupling and of Mulliken charges with a structure transformation. The Mulliken charge of Ti in the $\mathrm{Ti}{\mathrm{O}}_{6}$ octahedron increased in the ionicity with increasing pressure in the cubic phase. The bonding nature is changed with a decrease in the hybridization of the Ti-O bond and the localization of the electron density with increasing pressure. The hybridization decreases with pressure and disappears in the cubic paraelectric phase, which has a much more localized electron density distribution.

Revisiting the I{\overline {\bf 1}} structures of high-temperature Ca-rich plagioclase feldspar - a single-crystal neutron and X-ray diffraction study.

The I{\overline 1} structures of four natural Ca-rich plagioclase feldspars formed at high temperature were analysed using single-crystal neutron and X-ray diffraction. The neutron time-of-flight Laue diffractometer at the ORNL Spallation Neutron Source (Tennessee, USA) combined with a single-crystal X-ray diffraction instrument were able to reveal some new details about these already intensively studied structures. The split oxygen atoms refined from the neutron diffraction data show the underlying mechanism of Ca-Na ordering and the anisotropic P{\overline 1} ordering along the c-axis. The compositional ranges covered by the samples studied are quite rare for I{\overline 1} structures. The incommensurately modulated e2 structure of some plagioclase samples can easily be confused with an I{\overline 1} structure from the diffraction pattern, which puts some previously published I{\overline 1} structures into question. An incomplete phase diagram for Ca-rich plagioclase feldspar is proposed to explain the rarity of the I{\overline 1} structure in this compositional range, and a time-temperature-transformation diagram for the composition ∼An66 is provided accordingly.

Demonstration of a cold atom beam splitter on atom chip**Project supported by the State Key Basic Research Program of China (Grant No. 2011CB921504) and the National Natural Science Foundation of China (Grant No. 91536107).

We report an experimental demonstration of a new scheme to split cold atoms on an atom chip. The atom chip consists of a U-wire and a Z-wire. The cold atom cloud is initially loaded and prepared in the Z-trap, which is split into two separate parts by switching on the current of the U-wire. The two separate atom clouds have a distance more than one millimeter apart from each other and show almost symmetrical profiles, corresponding to about a 50/50 splitting ratio.

The age of radiance: the epic rise and dramatic fall of the atomic era

Radiation is a complex and paradoxical concept: staggering amounts of energy flow from seemingly inert rock and that energy is both useful and dangerous. While nuclear energy affects our everyday lives-from nuclear medicine and food irradiation to microwave technology-its invisible rays trigger biological damage, birth defects, and cellular mayhem. From the end of the nineteenth century through the use of the atomic bomb in World War II to the twenty-first century's confrontation with the dangers of nuclear power, Nelson illuminates a pageant of fascinating historical figures: Enrico Fermi, Marie and Pierre Curie, Albert Einstein, FDR, Robert Oppenheimer, and Ronald Reagan, among others. He reveals many little-known details, including how Jewish refugees fleeing Hitler transformed America from a country that created light bulbs and telephones into one that split atoms; how the most grotesque weapon ever invented could realize Alfred Nobel's lifelong dream of global peace; how emergency workers and low-level utility employees fought to contain a run-amok nuclear reactor, while wondering if they would live or die. Brilliantly fascinating and remarkably accessible, The Age of Radiancetraces mankind's complicated and difficult relationship with the dangerous power it discovered and made part of civilization.

Anharmonicity and isomorphic phase transition: a multi-temperature X-ray single-crystal and powder diffraction study of 1-(2'-aminophenyl)-2-methyl-4-nitroimidazole.

The harmonic model of atomic nuclear motions is usually enough for multipole modelling of high-resolution X-ray diffraction data; however, in some molecular crystals, such as 1-(2'-aminophenyl)-2-methyl-4-nitro-1H-imidazole [Paul, Kubicki, Jelsch et al. (2011 ▶). Acta Cryst. B67, 365-378], it may not be sufficient for a correct description of the charge-density distribution. Multipole refinement using harmonic atom vibrations does not lead to the best electron density model in this case and the so-called 'shashlik-like' pattern of positive and negative residual electron density peaks is observed in the vicinity of some atoms. This slight disorder, which cannot be modelled by split atoms, was solved using third-order anharmonic nuclear motion (ANM) parameters. Multipole refinement of the experimental high-resolution X-ray diffraction data of 1-(2'-aminophenyl)-2-methyl-4-nitro-1H-imidazole at three different temperatures (10, 35 and 70 K) and a series of powder diffraction experiments (20 ≤ T ≤ 300 K) were performed to relate this anharmonicity observed for several light atoms (N atoms of amino and nitro groups, and O atoms of nitro groups) to an isomorphic phase transition reflected by a change in the b cell parameter around 65 K. The observed disorder may result from the coexistence of domains of two phases over a large temperature range, as shown by low-temperature powder diffraction.

Nephelines from the Somma-Vesuvius volcanic complex (Southern Italy): crystal-chemical, structural and genetic investigations

Sixteen nephelines from different geological occurrences were sampled at the type-locality, the Somma-Vesuvius volcanic complex (southern Italy), and investigated for their chemistry and crystal structure obtained by both single-crystal and powder X-ray diffraction. Nepheline-bearing samples are metamorphic or from magmatic ejecta and pumice deposits. The lower K contents characterize the pumice- and some metamorphic-derived nephelines, whereas the higher ones are found in some samples from magmatic nodules. The amount of the anorthite molecule, quite low on average, can be more variable in the metamorphic nephelines. The crystal-structure investigations on Somma-Vesuvius samples compare well with previous studies of natural nephelines. All 16 nepheline samples adopt space group P63. The observed lattice parameters vary between 9.9768–9.9946 A (for a) and 8.3614–8.3777 A (for c), respectively. Furthermore, chemical analysis revealed that all specimens exhibit an excess of Si relative the ideal Si:Al ratio of 1:1. The analysis of the T-O distances in our samples clearly indicates a distinct ordering process of aluminium and silicon on the tetrahedral sites which is an agreement with Loewenstein’s rule. A linear correlation between the distance of symmetry equivalent split atoms O(1)-O(1)’ and the T(1)-O(1)-T(2) tilt angle was observed. The average (B = Na) distances of all crystals are very similar which is consistent with the outcome of the site population refinement indicating full occupancy with sodium. Oriented precession-type sections of reciprocal space indicated the presence of at least the most intense family of satellite peaks, demonstrating that this group of satellite reflections can occur not only in nephelines from pegmatites and ijolites but also in rocks from completely different petrological settings.

Facile Activation of Dihydrogen by a Phosphinito-Bridged Pt(I)−Pt(I) Complex

The phosphinito-bridged Pt(I) complex [(PHCy(2))Pt(mu-PCy(2)){kappa(2)P,O-mu-P(O)Cy(2)}Pt(PHCy(2))](Pt-Pt) (1) reversibly adds H(2) under ambient conditions, giving cis-[(H)(PHCy(2))Pt(1)(mu-PCy(2))(mu-H)Pt(2)(PHCy(2)){kappaP-P(O)Cy(2)}](Pt-Pt) (2). Complex 2 slowly isomerizes spontaneously into the corresponding more stable isomer trans-[(PHCy(2))(H)Pt(mu-PCy(2))(mu-H)Pt(PHCy(2)){kappaP-P(O)Cy(2)}](Pt-Pt) (3). DFT calculations indicate that the reaction of 1 with H(2) occurs through an initial heterolytic splitting of the H(2) molecule assisted by the phosphinito oxygen with breaking of the Pt-O bond and hydrogenation of the Pt and O atoms, leading to the formation of the intermediate [(PHCy(2))(H)Pt(mu-PCy(2))Pt(PHCy(2)){kappaP-P(OH)Cy(2)}](Pt-Pt) (D), where the two split hydrogen atoms interact within a six-membered Pt-H...H-O-P-Pt ring. Compound D is a labile intermediate which easily evolves into the final dihydride complex 2 through a facile (9-15 kcal mol(-1), depending on the solvent) hydrogen shift from the phosphinito oxygen to the Pt-Pt bond. Information obtained by addition of para-H(2) on 1 are in agreement with the presence of a heterolytic pathway in the 1 --> 2 transformation. NMR experiments and DFT calculations also gave evidence for the nonclassical dihydrogen complex [(PHCy(2))(eta(2)-H(2))Pt(mu-PCy(2))Pt(PHCy(2)){kappaP-P(O)Cy(2)}](Pt-Pt) (4), which is an intermediate in the dehydrogenation of 2 to 1 and is also involved in intramolecular and intermolecular exchange processes. Experimental and DFT studies showed that the isomerization 2 --> 3 occurs via an intramolecular mechanism essentially consisting of the opening of the Pt-Pt bond and of the hydrogen bridge followed by the rotation of the coordination plane of the Pt center with the terminal hydride ligand.

Crystal structure of the orthorhombicAl4(Cr,Fe) approximant of the Al–Cr–Fe decagonal quasicrystal

The crystal structure of the orthorhombic phaseAl4(Cr,Fe) with acomposition of Al80.6Cr10.7Fe8.7 has been determined by single-crystal x-ray diffraction (table 2). There are 11 crystallographically independent Cr/Fe sites, of which10 are icosahedrally coordinated. Of the 28 crystallographically independent Alsites 5 are icosahedrally coordinated. However, owing to the presence of manypartial occupancies, caused by split atoms, some of these coordinations are onlypseudo-icosahedral with effective coordination numbers (section 4.3). The icosahedral and pseudo-icosahedral clusters are oriented with a two-fold axisparallel to [100]. They are linked either by vertex-, edge- or face-sharing or by mutualinterpenetration, thus forming large clusters of icosahedra in the (100) layers with one of thefive-fold axes in the [010] direction. Four of the 12 atoms defining the vertices of anicosahedral cluster lie in a mirror plane (F plane), while the other atoms are in puckeredlayers below and above the mirror plane. Thus, the icosahedral cluster consists of layers of three atoms thick. Two such layers stack within one lattice constant nm. The interconnection of icosahedra in the layer block forms large triangular and hexagonal structural motifs, thoughthey have only two-fold rotational symmetry. Similar geometrical motifs butdisplaying three- or six-fold symmetry do exist in the structure of the hexagonalμ-Al4Mn,κ-(AlCrNi), λ-Al4Mn and ν-Al12Cr2Fe phases.

Positron beam investigations of natural cubic and coated diamonds

Positron beam and 2D-ACAR investigation of cubic and coated diamonds are reported. In type IIA diamonds, positrons are mostly trapped in vacancies in the carbon lattice; in type Ia diamonds, two main defect-related annihilation sites are nitrogen-vacancy complexes (H2, H3) and the vicinity of split interstitial atoms. No correlation between principal nitrogen defects and annihilation rate was found. PAS data indicate the presence of a significant amount of vacancies in all studied diamonds, which increases the rate of nitrogen aggregation. It is shown that pressurised fluid inclusions may serve as a positron trap, giving rise to the long component in the lifetime spectra.

Ternary Model of an Al-Cu-Co Decagonal Quasicrystal

We propose a structural model for decagonal Al-Cu-Co quasicrystals based upon existing experimental diffraction data supplemented by total energy calculations. The model is a decoration of tiles related to the Penrose rhombus tiling. Strong chemical ordering between Cu and Co leads to chains of alternating Cu and Co atoms. These chains project onto tile edges, where they define arrows. At low temperatures, the interatomic potentials lead to rules fixing the relative orientation of a majority of the arrows. These rules are a subset of the Penrose rhombus matching rules. [S0031-9007(98)06685-X] PACS numbers: 61.44.Br, 61.50.Lt, 61.43.Bn, 61.66.Dk More than a decade after the discovery of quasicrystals [1] answers are emerging to the fundamental problem of structure determination [2]. X-ray and neutron diffraction experiments successfully determine the location of the majority of atoms in quasicrystals [3]. Still, important questions remain. Quasicrystal structure refinements based on a finite number of diffraction peaks exhibit split atoms and atoms whose chemical identity cannot be determined [4,5]. Species determination is especially difficult for compounds such as Al-Cu-Co that contain elements near each other in a row of the periodic table, since their x-ray form factors are nearly equal. Furthermore, chemical disorder and partial occupancy are not well described. For example, a partially occupied site of high atomic number may mimic a fully occupied site of low atomic number. The atomicity condition is insufficient to resolve these issues; additional methods are required to investigate quasicrystal structure in greater detail. Techniques have been developed to supplement experimental diffraction data with total energy considerations to resolve the above difficulties [6 ‐ 8]. Here, we apply these techniques to create a model of the decagonal quasicrystal phase of Al-Cu-Co [9]. This phase exhibits quasiperiodic atomic layers stacked with a net 4 A periodicity in the perpendicular direction. We focus on this compound because its stable quasicrystalline phase has been well studied by diffraction, but experimental information suffers difficulties of the type described above. Furthermore, the existence of electronic-structure-based pair potentials for Al-Co alloys [10] allows total energy calculations to discriminate among candidate structures. We deduce the ternary alloy structure using only Al-Co binary potentials. After we review the current experimental knowledge of Al-Cu-Co decagonal phases, we discuss our computational method and then our results. Our results include an ideal hyperspace model and a corresponding real space structure. We describe the real space structure from two perspectives: linked clusters and space-filling tilings. We show that chemical ordering between Cu and Co enforces a subset of the Penrose matching rules. The temperature- and composition-dependent phase diagram of Al-Cu-Co alloys is well studied experimentally [11]. While the full composition range of thermodynamic stability of the decagonal phase shifts and widens as temperature increases, the principal domain of phase stability surrounds a straight line in the composition plane Al73.520.5xCuxCo26.520.5x ,

Structure analysis of [(NH4)1−xRbx]3H(SO4)2mixed crystals at 180 K

Abstract X-ray structure analysis of the [(NH4)1−xRbx]3H(SO4)2 mixed crystals with x = 0.57 was performed at 180 K in order to study the hydrogen bond character. The measurements were performed with the KUMA-4 single crystal diffractometer. The crystal structure was refined by using SHELXL93 program. At the room temperature and at 180 K the crystals are isostructural and belong to monoclinic system C2/c. The hydrogen bond distance R(O…O) at 180 K is 2.558(5)Å. The electron density of split hydrogen atoms in R(O…O) bonds has been observed on a differential Fourier map.

Grazing incidence X-ray diffraction on Cs/Ge(001)(2 × 1): evidence for cave site adsorption

Grazing incidence X-ray diffraction has been used to investigate the atomic structure of Cs adsorbed on Ge(001)(2 × 1) at room temperature. For about half monolayer coverage (1 monolayer = 6.25 × 10 14 atoms cm 2 for Ge(001)) the analysis of the data set consisting of 12 symmetry independent in plane ( Q Z = 0) reflections and of four fractional order reciprocal lattice rods (62 independent reflections in total) gave clear evidence for the occupation of the cave site which is in the groove between the dimer rows and above the 3rd layer Ge-atom. The Cs atoms are found to be strongly disordered along the surface normal. Within a static disorder model this is accounted for by splitting the Cs leading to different height levels, d ⊥ 1 = 1.73(11) Å and d ⊥ 2 = 0.44(11) Å above the Ge dimer level. Minimum Cs-Ge neighbor distances of R = 3.14(21) Å and 3.50(16) Å for the split atoms to nearest Ge atoms might indicate a mixed strength of interaction between adsorbate and substrate. A dynamical model allowing an unsplitted Cs atom to strongly vibrate along the surface normal by a root mean square amplitude of 〈u 33 2〉 1 2 = 0.93 Å leads to an equilibrium distance of R = 3.56(20) Å to second layer Ge also suggesting some charge transfer to the substrate. Whereas the Ge dimer bonding length is found not to be strongly affected by Cs adsorption ( R D = 2.45(11) Å), extensive relaxations are observed down to the 3rd substrate layer.

Variable-temperature X-ray diffraction analysis of the behavior of the mobile fluorine ions in a superionic conductor, β-PbF 2

We carried out single-crystal X-ray diffraction measurements of β-PbF 2 (quenched from 970 K) in the temperature range 131 to 298 K. The structure was refined to R = 0.008 at 131 K and R = 0.008 at 298 K by the least-squares methods, using about 80 reflections. The behavior of the one independent mobile fluorine ion could not be attributed to split atoms but instead was due to anharmonic thermal vibration.

EPR study of spin adducts of silyl and phosphonyl radicals with higher internal perfluoroalkenes

The EPR method was used to study the structure of spin adducts of silyl and phosphonyl radicals with higher internal perfluoroalkenes. The capacity for spin adducts to split off hydrogen atoms is determined by the degree of steric screening of the free radical center. The preparative photochemical reaction of hydrosilanes and dialkyl phosphites with perfluoro-4-methylpent-2-ene leads to regiospecific hydrosilylation and hydrophosphorylation products with yields up to 80%.

Structure Analysis and Hydrogen Bond Character of K3H(SO4)2

Structure analysis of K 3 H(SO 4 ) 2 was performed by X-ray diffraction experiments in order to study the hydrogen bond character in connection with the geometrical isotope effect. Crystal data at room temperature were obtained as a=9.777(1)Å, b=5.674(1)Å, c=14.667(4)Å, β=102.97(2)° and the space group A 2/ a , Z =4. The hydrogen bond length R OO determined from the positional parameters was 2.493(1)Å which was close to but still longer than the so called critical bond length r c . The electron density of split hydrogen atoms was observed on a differential Fourier map. It is concluded that the hydrogen atoms take the disordered state at room temperature and the distance between hydrogen atoms R HH is approximately 0.65 Å. The possibilities for the existence both of the low temperature phase and the high temperature prototype phase are discussed.