bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular structures of two indole alkaloids, evodiamine and rutecarpine, from evodia fruit
Authors: Hirayama N. , Fujii I. , Kobayashi Y.
Published: August 2006

Evodiamine,C19H17N3, is orthorhombic, P21212, a=13.654(2) Å, b=20.727(1) Å, c=5.2370(3) Å, V=1482.1(2) Å 3, Z=4. Rutecarpine, C18H13N3O, is monoclinic, P21/a, a= 26.909(1) Å, b=7.398(1) Å, c=14.468(1) Å, ß=98.672(5)°, V=2847.3(4) Å 3, Z=8. Although rutecarpine takes an essentially planar structure, evodiamine is folded in the middle of the molecule and the two halves are nearly perpendicular to each other. The marked differences of the three-dimensional structures is considered to be responsible for the significant difference of the body temperature retaining effects of these alkaloids.
Synthesis and properties of N1-(1,2,3,6-tetrahydrophthaloyl)semi- and thiosemicarbazides. II. Chiral N-substituted amides of 1-(3-ethylthio-1,2,4-triazol-5-yl)-4-cyclohexene-2-carboxylic acid
Authors: Wawrzycka I. , Koziol Anna E. , Galewicz Walesa K.
Published: August 2006

The structure of N-phenyl amide of 1-(3-ethylthio-1,2,4-triazol-5-yl)-4-cyclohexene-2-carboxylic acid (IIIe) has been determined by 1H NMR spectroscopy and X-ray crystallography. C17H20N4OS (328.4) is monoclinic, space group P1121/b with unit cell dimensions a = 11.530(1)Å, b = 9.685(4)Å, c = 16.486(2) Å, γ = 111.74(2)°, V = 1710.1(3) Å3, Z = 4, Dcalc. = 1.276 g cm-3. The triazole group and the N-phenyl amide are syn-oriented substituents of the cyclohexene ring. The relative configuration at the cyclohexene C(1´) and C(2´) asymmetric centers of the enantiomeric molecules in the racemic crystal is (1SR, 2RS). Molecules in the crystal structure form ribbons through intermolecular N-H···O and N-H···N hydrogen bonds. Selective interactions between the triazole···triazole and amide···amide fragments of alternatively arranged (R,S) and (S,R) enantiomers are observed.
The commensurately modulated structure of the lock-in phase of synthetic Co-åkermanite, Ca2CoSi2O7
Authors: Böhm H. , Riester M. , Petricek Václav
Published: August 2006

This paper deals with the structure determination of the lock-in phase of synthetic modulated Co-åkermanite, Ca2CoSi2O7. The structure determination of the (3 × 3 × 1) superstructure is based on X-ray data of a twinned single crystal taken at 130 K. The deformation modes in the commensurate lock-in phase are derived and compared with the deformations found by other authors in the incommensurate phase. A model for the driving force of the modulation in melilites in general is proposed: In order to release internal stress domains with clusters of 6-and 7-fold coordinated calcium are formed which are arranged in octagons.
Macrocyclic substructure of tricolorin A – The first crystal structure of a resin glycoside
Authors: Lehmann C.W. , Fürstner A. , Müller Th.
Published: August 2006

The structure of a tricolorin A derivative (11S)-11-[[4,6-O-benzylidene-β-D-glucopyranosyl-(1 → 2)-3,4-O-isopropylidene-β-D-fucopyranosyl]oxy]hexadecanoic acid 3gluc-lactone 2, a member of the resin glycosides, has been determined. This crystal structure is the first example for this class of natural products. At 100 K the lattice parameters in monoclinic space group P21 are: a = 22.502 (5)Å, b = 17.339( 4)Å, c= 25.011( 5)Å, β= 92.49(3)°, V = 9749(3)Å3 , Z = 10. M = 705.67, ρ= 1.202 Mg m -3 , μ = 0.087 mm-1 , F (000)= 3824. The five crystallographically independent molecules show upon superpositioning the expected preservation of the glycosidic link geometry, however the alkyl part of the macrocyclic ring expresses a larger degree of freedom while conserving gauche and anti conformations in six of nine torsion angles.
Prediction of the strains caused by magnetostatic Maxwell stresses at the surface of a para- or diamagnetic crystal
Authors: Kloos G.
Published: August 2006

Quantitative expressions for the strains caused by magnetostatic Maxwell stresses at the surface of a para- or diamagnetic crystal in a homogeneous magnetic field are given in terms of material constants and the magnetic field strength. The analysis is restricted to the longitudinal and transversal effect. The results obtained hold for any crystal symmetry and orientation.
Metastable ZrO2 crystal structures in electron beam evaporated thin films
Authors: Peneva S.K. , Gutzov S. , Djuneva K.D. , Atanasov G. , Marinova Ts.
Published: August 2006

Electron diffraction evidence for the existence of metastable ZrO2 in thin zirconia films grown by electron beam evaporation is presented. X-ray powder diffraction results show that the films are at the boundary of the amorphous/crystalline state of the matter. Micro-regions of unknown crystalline structures of ZrO2 are formed during the growth and are observed by transmission and reflection electron diffraction. Two CaF2-type zircon oxides exist inside the films. They are the known high temperature cubic phase with lattice parameter a = 5.09 ± 0.08 Å and an isostructural analogue with a = 5.40 ± 0.10 Å. Series of hexagonal and cubic close packed structures, believed to be related to the packing of clusters, are also detected. The existence of metastable zirconia structures is explained by Ostwald's rule of stages. A comparison of some of the metastable oxide structures of ZrO2 films with their isostructural analogues observed in SiO2 and SnO2 films is included.
An extremal principle for the phase problem of structures consisting entirely of spherically symmetric non-overlapping parts
Authors: Rothbauer R.
Published: August 2006

A simple extremal principle for the determination of the phases of the structure factors of a crystal is described. An empirical test is provided. An analytical theory of the extremal functions for phase determination is developed.
Hydroxylclinohumite, a new member of the humite group: Twinning, crystal structure and crystal chemistry of the clinohumite subgroup
Authors: Ferraris Giovanni , Prencipe M. , Sokolova E. , Gekimyants V.M. , Spiridonov E.M.
Published: August 2006

Hydroxylclinohumite Mg9[SiO4]4(OH, F)2, a new mineral from Zelentsovskaya mine near Magnitka (Zlatoust district, Southwestern Urals), is the OH-dominant equivalent of clinohumite Mg9[SiO4]4(F,OH)2. The crystal structure of hydroxylclinohumite has been refined from single-crystal X-ray data to R = 0.026 for the 1912 observed unique reflections [Fo > 4σ(Fo): a = 4.7480(3) Å, b = 10.2730(7) Å, c = 13.6894(2) Å, α = 100.72(1)°, V = 656.1(1) Å3, P21/b (No. 14), Z = 2]. Twinning on {001}, which apparently doubles the c axis, was detected and a ratio of 0.94:0.06 between the volumes of the two twin components has been obtained by least-squares refinement. The crystal structure of hydroxylclinohumite corresponds to that of clinohumite except for the positions of the hydrogen atoms. The crystal chemistry of the clinohumite subgroup is discussed and a general formula M2+
8(M2+, M4+) (SiO4)4(OH, F, O)2 (M2+ and M4+ mainly Mg and Ti, respectively) is proposed for it.
Structure of magnesiumphthalocyanine complexes
Authors: Mizuguchi J. , Matsumoto Shinya , Endo A.
Published: August 2006

Magnesiumphthalocyanine (MgPc; blue pigment) has attracted attention as a material useful for laser printers because of its near IR absorption. Two kinds of six-coordinate MgPc complexes have been grown from solution and their structures have been analyzed: MgPc/(H2O)2 (N-methyl-2-pyrrolidone)2 (crystal 1) and MgPc/(2-methoxyethanol)2 (crystal 2). The crystal data of crystal 1 are: MgPc/(H2O)2(NMP)2, Mr = 773.15, monoclinic, P21/n, a = 6.876(2) Å, b = 21.427(4) Å, c = 12.994(6) Å, β = 102.20(2)°, V = 1871(1) Å3, Z = 2, Dx = 1.375, Dm = 1.38 Mgm-3, graphite-monochromated MoK α, λ = 0.7107 Å, F(000) = 812.00, μ = 1.07 mm-1, T = 296 K, R = 0.074 for 1606 reflections. The crystal data of crystal 2 are: MgPc/(CH3OCH2CH2OH)2, Mr = 689.03, monoclinic, P21/n, a = 12.37(1) Å, b = 8.078(6) Å, c = 17.974(9) Å, β = 109.70(7)°, V = 1690(2) Å3, Z = 2, Dx =1.354, Dm = 1.37 Mgm -3, graphite-monochromated MoKα, λ = 0.7107 Å, F(000) = 720.00, μ = 1.08 mm-1, T = 296 K, R = 0.080 for 1407 reflections. In both complexes, the MgPc skeleton is found to be deformed as characterized by the molecular symmetry of Ci in contrast to D4h assumed for MgPc in the free space.
Physical properties of stable monoclinic and metastable trigonal 4-methylbenzophenone
Authors: Klapper Helmut , Kutzke H. , Haussühl Siegfried
Published: August 2006

Pyroelectric, dielectric and piezoelectric coefficients of metastable 4-methylbenzophenone, point group 3, have been determined by standard methods. Furthermore, thermal expansion and elastic properties of this phase and of the stable monoclinic phase have been studied. The pyroelectric effect is comparable with that of tourmaline, the piezoelectric effects to those of a-quartz. The differences between the two polymorphs with respect to thermal expansion and to elastic and thermoelastic properties are small, but nevertheless significant.
The chalcogenide phosphate apatites Ca10(PO4)6S, Sr10(PO4)6S, Ba10(PO4)6S and Ca10(PO4)6Se
Authors: Henning P.A. , Adolfsson E. , Grins J.
Published: August 2006

Four new apatitic phases were prepared and their structures determined. The structure of Ca10(PO4)6S was refined from single crystal X-ray data and the structures of Sr10(PO4)6S, Ba10(PO4)6S and Ca10(PO4)6Se from powder X-ray data using the Rietveld method.

The four apatites are isostructural and crystallize in the trigonal space group P-3 with the chalcogenide ion positioned at (0 0 ½). The sulfoapatites show no ability to absorb H2S in the way that oxyapatite absorbs H2O at elevated temperatures. This can be attributed to the position of the sulfide ion and the way it influences the crystal structure around the vacant chalcogenide position at (0 0 0).
Microstructural parameters and layer disorder accompanying dehydration transformation in Na-montmorillonite
Authors: Srivastava S.K. , Bala P. , Samantaray B.K. , Haeuseler Hartmut
Published: August 2006

Structural changes accompanying thermal transformation in Na-montmorillonite samples up to a temperature of 500°C have been investigated by X-ray line profile analysis. The method of Fourier initial slope and variance analysis of X-ray line profiles have been used to calculate the different microstructural parameters like crystallite size, r.m.s. strain (1/2), variation of inter layer spacing (g), fraction of planes affected by such defects (γ), etc. at different stages of the dehydration process. The dehydration mechanism also has been explained based on thermogravimetric analysis (TGA).
Contribution to the crystal chemistry of rare-earth chalcogenides. II The crystal structure and twinning of rare-earth diusulfide PrS2
Authors: Tamazyan R. , Arnold H. , Molchanov V. , Kuzmicheva G. , Vasileva I.
Published: August 2006

The structure of the presodyme disulfide PrS2 has been determined and refined by the LS method in space group P21/b11(14) with a=4.054(1) Å; b=8.058(1) Å; c=8.079(1) Å and α=90.08(2)° to the final values of discrepancy factors R=0.188; Rw=0.0204. The structure is a derivative structure of the ZrSSi (or PbFCl) structure type. A heringbone pattern of S2
2- dumbbells with interatomic distance 2.135(1) Å is observed in the planes parallel to (001). The investigated crystal has been twinned by pseudomerohedral law, the twin symmetry is mmm and the twinning symmetry elements are (010) and (001) mirror planes.
Confirmation by an X-ray crystallography study of a molecular modeling prediction about the coordination scheme of a new (1,4,8,11-(tetra-2-carboxyethyl)-1,4,8,11-tetraazacyclotetradecane)cerium(III) complex
Authors: Lecomte Claude , Dahaoui-Gindrey V. , Barbette F. , Pullumbi P. , Gros C.P. , Guilard R. , Dahaoui Slimane
Published: August 2006

The synthesis and characterization of a new cerium(III) complex with the ligand 1,4,8,11-(tetra-2-carboxyethyl)-1,4,8,11-tetraazacyclotetradecane (TETP), Ce(C22N4O8H38)(NO3)(H2O)3 · 3 H2O, is described. The cerium ion is eight-coordinated, linked to four carboxyl oxygen atoms belonging to four different TETP macrocycles as well as to three solvate water molecules, and to one oxygen atom of a disordered NO3
- anion. Each asymmetric unit consists of two different half TETP ligands. Each centrosymmetric TETP macrocycle possesses a [3434] conformation, two propionate arms being extended and the others folded towards two protonated nitrogen atoms. The four functionalized chains of the ligand whatever their conformation (extended or folded) are involved in the coordination polyhedron of cerium ion. This coordination mode was predicted from Molecular Electrostatic Potential calculations which showed the more negative potential sites of the ligand where the lanthanide cation would approach and coordinate.
Crystal structures of Cd(ReO4)2 · 4Urea, Cd(ReO4)2 · 6Urea and Ca(ReO4)2 · 5Urea. Synthesis and characterization of urea adducts from the systems M(ReO4)2-Urea-H2O, M = Ca, Sr, Ba, Pb and Cd
Authors: Petrova R. , Todorov T. , Bakardjieva S. , Mihailova Boriana , Angelova O.
Published: August 2006

The crystal structutes of Cd(ReO4)2 · 4Urea, Cd(ReO4)2 · 6Urea and Ca(ReO4)2 · 5Urea were solved. Cd(ReO4)2 · 4Urea consists of discrete neutral [Cd(ReO4)2L4] (L = Urea) clusters. Ca(ReO4)2 · 5Urea and Cd(ReO4)2 · 6Urea are built up of cationic [Ca(ReO4)L5]+ and [CdL6]2+ clusters, respectively, and ReO4- anions, interlinked by an extensive network of H-bonds. The octahedral coordination of M atoms is most regular in Cd(ReO4)2 · 6Urea and most distorted in Ca(ReO4)2 · 5Urea.

With the synthesis and X-ray analysis of these new urea adducts the investigation of the systems M(ReO4)2-Urea-H2O, M = Ca, Sr, Ba, Pb and Cd, was accomplished. This paper represents and a review of the synthesis, X-ray study and IR characterisation of the stable phases from the mentioned systems.
Strukturverwandtschaften zwischen cis-Natriumhyponitrit und den Alkalimetallcarbonaten M2CO3 (M = Na, K, Rb, Cs) dargestellt durch Gruppe-Untergruppe Beziehungen
Authors: Jansen Martin , Feldmann C.
Published: August 2006

The crystal structures of cis-sodium hyponitrite and the alkalimetal carbonates M2CO3 (M = Na, K, Rb, Cs) are closely related to each other. The monoclinic space groups of cis-Na2N2O2, γ-K2CO3, Rb2CO3, Cs2CO3 (all P121/c1), β-K2CO3 (C12/c1) and β-/γ-Na2CO3 (C12/m1) are subgroups of the common supergroup Cmcm. The ‘aristo-type’ of all of these structures is represented by α-Na2CO3 and α-K2CO3 crystallizing in P63/mmc. At comparing the monoclinic crystal structures of cis-Na2N2O2, β-Na2CO3 and Rb2CO3 it becomes evident that the reduction of symmetry with respect to the supergroup Cmcm is related to the size of the alkalimetal cation in the case of the carbonates, whereas in cis-Na2N2O2 it is due to the different shape of the N2O2
2- as compared to the CO3
2- anion.
The crystal chemistry of superconducting Sr3.66Bi0.28Ca6.02Cu16.45O28.63 and nonsuperconducting Sr5.97Ca3.13Y0.53Al0.25Bi0.12Cu16.66O28.64 compounds
Authors: Shvanskaya L. , Leonyuk L. , Sokolova E. , Maltsev V.
Published: August 2006

The title compounds from the family of the [M2Cu2O3]5[CuO2]7-type cuprates were synthesized by the flux growth method in the system SrCO3-CaO-Bi2O3-CuO. The crystal structures of Sr3.66Bi0.28·Ca6.02Cu16.45O28.63 (SC) and Sr5.97Ca3.13Y0.53Al0.25Bi0.12·Cu16.66O28.64 (non-SC) were determined. SC: Space group F222, a=11.319(2) Å, b=12.763(2) Å, c=19.491(12) Å, Z=4, R=0.0811 based on 802 reflections with F>4 σ (F). Non-SC: Space group F222, a=11.346(3) Å, b=12.996(3) Å, c=19.585(9) Å, Z=4, R=0.0769 based on 736 reflections with F>4 σ(F). The first crystal (SC) is superconducting (Tc=80K). The structural differences for two compounds in questions have been established: the Cu-Cu distances from the Cu atoms of a ladder plane to the Cu atoms of the ribbons and the bond distances from Cu to the apical oxygen at the plane of the Cu-O ribbons are smaller in the SC compound as compared with those in the non-SC phase.
The bond character of rutile type SiO2, GeO2 and SnO2 investigated by molecular orbital calculation
Authors: Yamanaka T. , Mimaki J. , Tsuchiya T.
Published: August 2006

Molecular orbital calculations using descrete-variational Xα method were carried out in order to investigate the bond nature of SiO2, GeO2 and SnO2. The bond overlap populations and the d-orbital populations of cations were decreased with increasing the atomic number. The deformation density maps of electronic charge show the accumulation of electron in interatomic region which is most dominant in SiO2. The calculated density of states indicates that the bond character of SiO2 is more covalent than that of GeO2 and SnO2. From the excited d-electron partial density of states, it is inferred that the Si excited-3d has some connection with the bond nature of SiO2 covalency.
Crystal-chemical characterization of mixed-valent indium chalcogenides by X-ray absorption spectroscopy (EXAFS)
Authors: Epple M. , Panthöfer M. , Walther R. , Deiseroth H.J.
Published: August 2006

The mixed-valent indium chalcogenides InTe, In4Se3, In4Te3, In6S7 and In6Se7 were studied together with b-InS3 and TlInS2 by In and Te K-edge EXAFS spectroscopy. These well-characterized crystalline solids were chosen as model systems to assess the general applicability of EXAFS for structural studies of first order mixed-valent solids containing indium. The question was whether the interatomic distances and coordination numbers derived from EXAFS data could be used for a basic structural characterization in the sense of "structural fingerprints" to identify the indium species present in a given sample. Indium species in the samples comprised In+, In3+, (In2)4+ and (In3)5+, with up to 3 of them being simultaneously present. While the analysis of compounds with only one indium species was possible with high accuracy, it was impossible to interpret the EXAFS data of complex mixed-valent solids containing three different indium species (e.g. In+, In3+, (In2)4+) without prior knowledge of the crystal structures. Intermediate cases are those compounds in which two indium species are present, e.g. In3+ in tetrahedral and octahedral coordination or In+ in a highly regular coordination accompanied by In3+. In conclusion, EXAFS measurements alone can be a reliable basis for structural discussions beyond the first coordination sphere only for compounds of moderate complexity. In most cases prior information of structural data from single crystals or other sources is necessary. This is particularly relevant for future experiments with amorphous or poly-crystalline samples that cannot be studied with standard diffraction techniques.
Structure and charge density studies on 1,1-difluoroallene and tetrafluoroallene
Authors: Luger P. , Buschmann J. , Koritsánszky T. , Lentz D. , Nickelt N. , Willemsen St.
Published: August 2006

Single crystals of 1,1-difluoroallene and tetrafluoroallene (mp 136 K and 108 K) were grown in situ on a four-circle diffractometer from the liquid substance in a cold N2 gas stream. The crystal and molecular structures of the two compounds were determined by X-ray crystallography at 95(2) and 100(2) K, respectively. The molecule of 1,1-difluoroallene has an almost linear C=C=C framework, while for tetrafluoroallene exact linearity is provided by the 222 crystallographic site symmetry. In agreement with theoretical calculations, the C=C bond lengths decrease with increasing number of fluorine substituents. For difluoroallene a collection of high order data (sinθ/λmax = 1.0 Å1) was possible allowing for the determination of its charge density. The topological analysis of this function was performed and the results were compared to those obtained by quantum-chemical calculations.
In situ electron diffraction study of synthetic (Ca1-xSrx)2MgSi2O7 åkermanites
Authors: Rager H. , Schosnig M. , Schaper A.K. , Kutoglu A. , Treutmann W.
Published: August 2006

This paper deals with transmission electron microscope experiments of Ca,Sr-åkermanite solid solutions at temperatures between 100 K and 375 K. The aim of the investigations was to study the compositional and temperature dependence of phase transitions from the normal to the incommensurately modulated structure of

(Ca1-xSrx)2MgSi2O7 single crystals observed by electron diffraction. With increasing Sr-content the normal to incommensurate phase transition temperature decreases linearly from ca. 350 K (x = 0.04) to 295 K (x = 0.22). Depending on temperature and composition, the incommensurate phase is structurally not uniform, its stability field can be divided into two regions. The transition between the two regions can be recognized by the additional appearance of higher order satellite reflections in the diffraction pattern. Additionally, the transition is characterized by an abrupt change of the modulation wavelength. Within the high-temperature, low ordered region, the modulation wavelength varies between 18.5 Å and 20.5 Å, whereas no changes of the wavelength have been found in the low-temperature, higher ordering region. With increasing Sr-content the high-temperature, low ordered phase covers a steadily increasing temperature range.
Strategies for data collection on a CCD-diffractometer
Authors: Bolte M. , Rühl S.
Published: August 2006

The introduction of area detectors has led to a significant reduction of the time needed for measuring a complete set of X-ray reflections. The default parameters suggested by the manufacturer of the instrument lead to good results, but both the software and the hardware provide the possibility of varying numerous parameters in order to optimize the quality of the data set. The influence of parameters (measuring time, scan angle, crystal-to-detector distance, collimator radius, detector resolution, redundancy, crystal size and scan type) is determined and rated with regard to their importance for the quality of the data. The investigations were carried out on a Siemens (now Bruker AXS) CCD diffractometer on three small organic molecules, p-nitrobenzaldehyde diacetate [P21/n; Z=4; a=10.785(2) Å; b=7.420(2) Å; c=15.407(2) Å;β=107.30(1)°] and p-methoxyacetophenone [P21/c; Z=4; a=10.158(2) Å; b=7.917(2) Å; c=10.287(2) Å; β=103.72(3)°], of which the crystal structures were determined. An optimized strategy for the data collection is proposed and the attainable improvement is shown by comparing the data sets based on the default parameters and the data sets obtained with the optimized strategy for the three structures examined. However, different strategies may be needed for more strongly absorbing materials.
Crystal structure and crystal chemistry of biehlite, Sb1.79As0.21MoO6
Authors: Adiwidjaja G. , Friese Karen , Klaska K.-H. , Schlüter J. , Czank M.
Published: August 2006

The new mineral biehlite was found in the Tsumeb mine, Namibia and has the composition Sb1.79As0.21MoO6. It crystallizes monoclinic, space group C2/c with lattice paramters a=18.076(5)Å, b= 5.920(5)Å, c=5.083(5)Å, β= 96.97(1)°. Refinement led to a final R(F) value of 0.065 for 679 symmetrically independent reflections.

[MoO6]6- octahedra share common edges and form zigzag chains which run parallel to the c direction. The octahedra are flanked by a [Sb2O2]2+ group on each side and infinite ribbons of composition [Sb4Mo2O12] are obtained. Neighbouring ribbons are only held together by weak Sb-O bonds in the directions of a and b.

The [MoO6]6- octahedra are strongly distorted with Mo-O distances ranging from 1.700(5) to 2.248(6) Å and O-Mo-O angles between 72.1(2)° and 105,3(4)°. The common O-O edge (2.492(8)Å) is shortened with respect to the remaining edges of the octahedra (2.704(8)Å-2.899(8)Å).

The Sb-cation forms three short bonds with oxygen at distances slightly smaller than 2Å. Six further oxygen atoms are located at distances ranging from 2.910(6) to 3.470(6)Å. Calculated distance for the lone-pair is 1.18 Å. Part of the Sb3+ is substituted by the smaller As3+ ion. The relationship of the new mineral to similar structures – especially to the mineral stibivanite and the synthetic compound Sb2MoO6 – are discussed.
Calculation of Gibbs Energies of Hydration of Monovalent Ions: Examination of Born Equation and its Reevaluation
Authors: Lahiri Sujit Chandra
Published: August 2006

The limitations of Born equation and its different modifications for the calculation of Gibbs energies of hydration of ions have been briefly reviewed. A modified method for the calculation of hydration energies of ions has been suggested. The hydration energies thus obtained have been compared with the data in the literature.
Comparative Studies on the Complex-Formation Equilibria of Mercury(II) with Acetylcysteine and Captopril
Authors: Köszegi-Szalai H. , Paál T.L. , Barcza L.
Published: August 2006

The complex-formation equilibria of mercury(II) with acetylcysteine and captopril have been studied by pH-metric and liquid-liquid extraction methods applying dithizone as a competitive ligand during the latter measurements. The stability constants of three differently protonated Hg(II)/ligand 1:2 complexes of extreme stability have been determined by the combination of extraction and pH-metric data.

The formation of the less stabil Hg(II)-ligand 1:3 complexes with the coordination of three sulfhydrilate groups has been followed and the values of β

The differences in the Hg(II) complex formation and protonation equilibria between the two ligands and the possible binding sites in the complexes have been discussed.
Nonlinear Vibrations in a 2-Dimensional Protein Cluster Model with Linear Bonds
Authors: Shidlovskaya E.G. , Schimansky-Geier L. , Romanovsky Yu.M.
Published: August 2006

A two dimensional model for the substrate inside a pocket of an active site of an enzyme is presented and investigated as a vibrational system. The parameters of the system are evaluated for α-chymotrypsin. In the case of internal resonance it is analytically and numerically shown that the energy concentrated on a certain degree of freedom might be several times larger than in the non-resonant case. Additionally, the system is driven by harmonic excitations and again energy due to nonlinear phenomena is redistributed inhomogeneously. These results may be of importance for the determination of the rates of catalytic events of substrates bound in pockets of active sites.
Electrodeposition of CdSe Films: In-Situ Study by Spectroscopic Ellipsometry
Authors: Reck J. , Beck U. , Dohrmann J.K.
Published: August 2006

CdSe films grown on Ti-coated polished steel by constant-current deposition from an aqueous solution containing selenosulfite and cadmium nitrilotriacetate have been studied by spectroscopic ellipsometry under
Kinetic Analysis of Complex Chemical Activation and Unimolecular Dissociation Reactions using QRRK Theory and the Modified Strong Collision Approximation
Authors: Chang A.Y. , Bozzelli J.W. , Dean A.M.
Published: August 2006

A method to predict temperature and pressure-dependent rate coefficients for complex bimolecular chemical activation and unimolecular dissociation reactions is described. A three-frequency version of QRRK theory is developed and collisional stabilization is estimated using the modified strong-collision approximation. The methodology permits analysis of reaction systems with an arbitrary degree of complexity in terms of the number of isomer or product channels. Specification of both high and low pressure limits is also provided. The chemically activated reaction of vinyl radical with molecular oxygen is used to demonstrate the approach. Subsequent dissociation of the stabilized vinyl peroxy radical is used to illustrate prediction of dissociation rate coefficients. These calculations confirm earlier results that the vinoxy + O channel is dominant under combustion conditions. The results are also consistent with RRKM results using the same input conditions. This approach provides a means to provide reasonably accurate predictions of the rate coefficients that are required in many detailed mechanisms. The major advantage is the ability to provide reasonable estimates of rate coefficients for many complex systems where detailed information about the transition states is not available. It is also shown that a simpler 1-frequency model appears adequate for high temperature conditions.
Internal Conversion with 3,5-Dimethyl-4-(methylamino)benzonitrile in Alkane Solvents
Authors: Rückert I. , Hebecker A. , Parusel A.B.J. , Zachariasse K.A.
Published: August 2006

With 3,5-dimethyl-4-(methylamino)benzonitrile (MHD) in n-hexane and n-hexadecane at 25°C, relatively small values are obtained for the fluorescence quantum yield Φ
Magnetic Resonance of 3He and 129Xe in Aqueous Solutions Containing Paramagnetic Mn2+ and Co2+ Ions. A Comparisonwith Isoelectronic 7Li+ and 133Cs+ Ions
Authors: Mazitov R. , Seydoux R. , Diehl P. , Enikeev K. , Il`yasov A. , Haselmeier R.
Published: August 2006

The chemical shifts and relaxation times T
Anisotropies of the Reorientational Motion of Deuterated and Protonated Benzene by 13C Nuclear Magnetic Relaxation
Authors: Hardy E.H. , Merkling P.J. , Witt R. , Dölle A.
Published: August 2006

The reorientational motion of protonated and deuterated benzene in the neat liquid was investigated by
Dynamical and Quantumchemical Characteristics of Electronic Charge Density Transfer Processes
Authors: Lorenz Wolfram
Published: August 2006

Exploration of electronic charge transfer requires quantumtheoretical support. On the line of previous work, the dynamical and quantumchemical foundation of electronic charge density transfer, or partial charge transfer in condensed-matter chemical processes, is explicated in terms of charge density conservation and local completeness of finite LCAO expansion. Accompanying discussion is focussed on recent
Raman Spectroscopic Studies of Scandium(III) Hydration in Aqueous Solution - about the First Hydration Sphere of Sc(III) in Solution
Authors: Rudolph W.W.
Published: August 2006

It has been shown conclusively that Sc(III) in aqueous perchlorate solution occurs as an hexaaqua cation. The weak, polarized Raman band assigned to the

Besides the polarized component at 442 cm

These findings are also in contrast to the results found in Sc
Ion-Induced Random Electric Fields in Aqueous Salt Solutions as Studied by the Four-Photon Polarization Spectroscopy Method
Authors: Bunkin N.F. , Lobeev A.V.
Published: August 2006

Using the four-photon polarization spectroscopy we have studied the Rayleigh wing spectral patterns of several aqueous salt solutions within the 0-50 cm
Structure and Properties of Calcium Pyruvate in Aqueous Solutions
Authors: Paradies H.H. , Quitschau P. , Pischel I.
Published: August 2006

The dynamic behaviour of calcium pyruvate, Ca(pyr)
Particle Entropies and Entropy QuantaII. The Photon Gas
Authors: Zimmermann Helmuth W.
Published: August 2006

We consider a photon gas, which is enclosed in a cavity and is in thermal equilibrium at temperature T. Each photon has a particle entropy σ = ka and a particle energy ε = hv = cp. The particle entropy σ is measured by the dimensionless number a in multiples of the Boltzmann constant k, which serves as an atomic entropy unit. The particle energy ε is related to the frequency Þgn and the momentum p of the relativistic photons, c velocity of light. Particle entropy and particle energy are connected by the temperature, ε = σT. Applying statistical thermodynamics we obtain the thermodynamics of the photon gas, written in particle entropies a. We also get the Planck distribution, and the Planck, Stefan-Boltzmann, and Wien radiation law. - The total entropy S of the photon gas is composed of two parts S
Adsorption Activity of Cu, Au and Ni Solid Electrodes in Molten Carbonates
Authors: Stepanov V.P. , Yakshevich I.V. , Belyaev V.S.
Published: August 2006

The surface energy, the electric double layer capacity and the "estance´´ (the charge derivative of the surface tension) were analyzed as a function of the electric potential across copper, gold and nickel solid electrodes in the eutectic melt 62 mol% Li
Evidence for Chiral Isomers in the Spectra of Small Size Selected Hydrazine Clusters
Authors: Beu T.A. , Buck U.
Published: August 2006

New configurations of hydrazine (N
SAXS Spectrometer for High Temperature Studies of Fluids
Authors: Steininger R. , Freyland Werner
Published: August 2006

A new construction of a high temperature set-up for small angle X-ray scattering (SAXS) measurements on corrosive and volatile fluid systems is presented. The sample cell from single crystal sapphire is sealed with a special metal wire technique. The cell with the surrounding high temperature furnace is integrated in a homemade SAXS-spectrometer. This technique has been employed up to 1000°C for the example of SAXS-measurements on fluid K
Are Primary Quantum Yields of NO2 Photolysis at λ ≤ 398 nm Smaller than Unity?
Authors: Troe Jürgen
Published: August 2006

Primary quantum yields Φ of NO
Anion Rotation and Cation Transport in the Rotor Phase α -Sodium Orthophosphate: Paddle-Wheel Mechanism Redefined in View of New Experimental Results
Authors: Witschas M. , Eckert Hellmut , Wilmer Dirk , Banhatti R.D. , Funke H. , Fitter J. , Lechner Ruep E. , Korus G. , Jansen Martin
Published: August 2006

The high-temperature phase of sodium ortho-phosphate, α -Na
Phase Diagrams in Volume, Mole Fraction Coordinates
Authors: Lentz H.
Published: August 2006

For a binary mixture the V,x-diagram with isotherm and isobaric curves contains the complete information about the phase behavior of the system. In ternary mixtures isotherm and isobaric surfaces and additional information on the tie lines describe the complete phase behavior.

For a binary mixture the V,x-phase diagrams corresponding to the classified P,T-phase diagrams are shown. The constitute binary V,x-phase diagrams and partly the critical V,x-surfaces of the ternary systems are shown for NH
Impedance of the Hydrogen Polymer Fuel Cell Electrode. Theory and Experiments
Authors: Kjelstrup S. , Pugazhendi P: , Bedeaux D.
Published: August 2006

We derive the impedance for the hydrogen electrode in the polymer membrane fuel cell from irreversible thermodynamics. The results predict a surface contribution to the cell impedance that can give two semi-circles in the Nyquist diagram. The equivalent circuit of the impedance is shown. The high-frequency contribution is connected to the oscillation of dipoles consisting of free charges in the surface, while the low-frequency contribution is connected to the electrochemical reaction. This can be explained by a slowly relaxing proton conducting polymer network at the reaction site.
Hydrophobic Interactions in Solution: A Nuclear Magnetic Resonance Approach
Authors: Sacco A.
Published: August 2006

The self-association behaviour of relatively small hydrophobic organic components in aqueous mixtures has been investigated by the application of an NMR technique. The association A
On the Structure of Shear-Ordered Polymer Dispersions
Authors: Versmold H. , Dux Ch. , Musa S.
Published: August 2006

The present paper is concerned with the structure of colloidal dispersions consisting of charged polymer particles. The scattering of light, neutrons or X-rays from such latex dispersions is best described in the reciprocal lattice. Two quantities of central importance will be introduced: the particle form factor P(Q) and the interparticle structure factor S(Q). In the present treatment we show that the structure can be adequately accounted for by introducing a redefined symmetry adapted aggregate structure factor. According to the structure of interest these aggregate structure factors are one-dimensional (string-like), two-dimensional (layer-like) or three-dimensional (crystal-like). The description appears particularly suited to account for systems under sheared conditions. In the final section we present experimental neutron scattering results. A structural change is observed as a function of the shear rate γ°. The occurrence of the structural change and its relation to the 'self´ part of the previously introduced aggregate structure factor are considered.
Testing Intermolecular Potentials with Scattering Experiments: He-CO Rotationally Inelastic Collisions
Authors: Bodo E. , Gianturco F.A. , Paesani F.
Published: August 2006

A recent set of experimental data which gave new state-to-state He-CO rotationally inelastic integral cross sections at two different collision energies is examined in the present study using a potential energy surface obtained by us which combines Density Functional Theory (DFT) methods with dispersion interaction corrections. Computations with exact quantum dynamical coupling indicate that the DFT-DISP approach generates a model potential which agrees with the experiments more closely than two of the most accurate potential functions which already exist for the title system. The implications of the present results are extended by also calculating state-to-state differential cross sections and rotational relaxation/excitation rates at low temperatures. The quality of the potential well produced by the present model is further tested by calculating the structure of its rovibrational bound states.
Temperature Dependence of Collisional Energy Transfer in Highly Excited Aromatics Studied by Classical Trajectory Calculations
Authors: Grigoleit U. , Lenzer T. , Luther K.
Published: August 2006

The temperature dependence of the gas-phase collisional relaxation of highly vibrationally excited aromatic molecules has been studied using large scale classical trajectory calculations. The investigations have focused on azulene collisions with different colliders (He, Ar and N
High Resolution Electron Ionization of N2O Clusters: Appearance Energies
Authors: Hanel G. , Fiegele T. , Stamatovic A. , Märk T.D.
Published: August 2006

Electron ionization cross sections for (N

Comparison of the presently derived appearance energies with earlier photoionization data shows a distinct difference in corresponding values attributed to different ionization mechanisms. Both data sets can be fitted successfully by a n
Direct Measurements of the Reaction NH2 + H2 → NH3 + H at Temperatures from 1360 to 2130 K
Authors: Friedrichs G. , Wagner H.Gg.
Published: August 2006

The reaction NH

According to recent literature values the reverse reaction NH
New Scheme for Measuring the Angular Momentum Spatial Anisotropy of Vibrationally Excited H2 via the I 1Πg State
Authors: Fernández-Alonso F. , Bean B.D. , Ayers J.D. , Pomerantz A.W. , Zare R.N.
Published: August 2006

We report the spectroscopic detection of vibrationally excited molecular hydrogen using 2+1 resonantly enhanced multiphoton ionization (REMPI) via the I
Periodic Nanostructures
Authors: Apel O. , Beinhorn F. , Ihlemann J. , Klein-Wiele J.-H. , Marowsky G. , Simon P.
Published: August 2006

We report on the fabrication of periodic nanostructures on selected materials by short-pulse uv-laser ablation. Temporal studies reveal details of the ablation process with sub-picosecond time resolution. Biochemical applications of the nanostructures for planar waveguide technology are presented.
Global Geometry Optimization of Molecular Clusters: TIP4P Water
Authors: Hartke B.
Published: August 2006

In this paper, we present an extension of our phenotype algorithm for global cluster geometry optimization from atomic clusters to the more difficult molecular clusters. A successful application to the benchmark case of TIP4P water clusters shows that the new method is at least as good as one of the best methods in the literature so far. We point out why the TIP4P water cluster system starts to become very complicated beyond twenty water molecules and follow the traces of a beginning structural transition from clusters with all water molecules at the surface to clathrate-like cages with a truly interior water molecule.
Molecular Dynamics Simulation of Femtosecond Pump-Probe Experiments on I2 in Ar Environments
Authors: Ermoshin V.A. , Engel V.
Published: August 2006

We present the application of classical molecular dynamics methods to the simulation of femtosecond time-resolved experiments. Choosing I
Guided-Ion Beam Measurements of Ar+ + Ar Symmetric Charge-transfer Cross Sections at Ion Energies Ranging from 0.2 to 300 eV
Authors: Pullins S.H. , Dressler R.A. , Torrents R. , Gerlich D.
Published: August 2006

Guided-Ion Beam (GIB) measurements of the Ar
NMR Study of Hydrogen Bonding Association of 2-Isopropylphenol in Carbon Tetrachloride, Acetone, Dimethyl Sulphoxide and Acetonitrile
Authors: Luo W.-C. , Lay J.-L. , Chen Jenn-Shing
Published: August 2006

This study investigates the association of 2-isopropylphenol through hydrogen bonding in carbon tetrachloride, [2H6]acetone, [2H3]acetonitrile and [2H6]dimethyl sulphoxide by using high resolution nuclear magnetic resonance spectroscopy. Chemical shifts of the hydroxyl proton were measured over a wide range of temperature and concentration. The chemical shift data were treated by a graphical method to determine the monomer shift, dimer shift and dimerization constant. The enthalpy and entropy of dimerization were determined via a van´t Hoff plot from the temperature variation of the dimerization constant.
Nonmetal-Metal Transition in Liquid Cu-Based Alloys
Authors: Sklyarchuk V. , Plevachuk Y.
Published: August 2006

Electrical conductivity σ(T) and thermo-e.m.f. S(T) measurements were performed for ternary Cu-based chalcogenides in a wide temperature range. A concentration range of the semiconductor-metal transition has been determined. A radical alteration in the electron spectrum occurs in the region of x = 0.6-0.8, namely, a semiconductor-metal transition takes place. Complete metallization of alloys takes place with temperature increasing. Further heating is accompanied by electrical conductivity decreasing followed by final exponential electrical conductivity dependence with seeming negative activation energy, while thermopower increases without changing a sign. This process is accompanied by an increase of a free electrons concentration. At the same time, at higher temperatures when the alloy’s density decreases, localization of the wave functions of electrons on separated atoms or atoms groups caused by density fluctuations, occurs. For alloys with Se content, the electrical conductivity decreasing caused by thermal expansion, could be intensified at the expense of molecular units formation. A simultaneous density decreasing causes an appearance of small dynamic groups like Se2, Se3, Se6. While similar molecular complexes appear, a very inhomogeneous in a structural and energy sense system in being formed. Peculiarities of the reverse metal-semiconductor transition were studied.
Classification of Dioxygen Reactions: A Unifying View
Authors: Wagnerova D.M.
Published: August 2006

Dioxygen reactions in solution were classified into six classes according to two criteria, the way how the spin ban of dioxygen reaction is circumvented and origin of the activation energy - thermal energy or energy of the light quantum.
Topography of the Electron Momentum Density in Linear Molecules
Authors: Thakkar A. J.
Published: August 2006

The Hessian of the electron momentum density Π(
Visualizing Covalency and Multiple Bonds in Terms of the Electronic Single-Particle Density Matrix
Authors: Asthalter T. , Walter M.
Published: August 2006

Two-dimensional cuts through spin-integrated single-particle density matrices (SPDMs) have proven to be a valuable tool to discuss the nature of chemical bonding independent of the degree of rotation of the underlying orbitals in Hilbert space. Starting from a straightforward concept for the interpretation of σ bonds, we briefly present how the transition from purely ionic to mainly covalent bonding is mirrored in the off-diagonal features of the SPDM in the isoelectronic series LiF, BeO and BN. Furthermore, we outline one of several possible ways to extend the graphical representation and interpretation of SPDMs to the case of π bonds in organic molecules and apply it to the conjugated π-electron system 1,6-hexadiynediol.
The Structure of Electronic Moyal Functions, and their Connection with Experiment
Authors: Schmider H. L.
Published: August 2006

The Moyal Function is a phase-space representation of the reduced one-particle density matrix that is particularly close to experimental quantities. We discuss basic structural features of this function for atoms and molecules, and point out a direct connection to the “non-diagonal Compton profile” obtained from coherent inelastic scattering by Schülke
Compton Spectroscopy and Chemical Bonding
Authors: Shukla A. , Barbiellini B. , Buslaps T. , Suortti P.
Published: August 2006

In this article we show with the help of two examples how Compton spectroscopy may be used to study the effect of chemical bonding in materials as diverse as a molecular crystal and a high temperature superconductor. Compton spectroscopy has a long history as an investigative method in condensed matter physics and in fact the realisation that the Compton profile is sensitive to the effects of chemical bonding dates back at least fifty years. In the seventies, through the efforts of Weyrich [1] and others [2,3], practical applications of this realisation were first achieved. We argue that such studies are more and more relevant thanks to the availability of synchrotron radiation and efficient computational tools.
The Spectral Momentum Density of Aluminium, Copper and Gold Measured by Electron Momentum Spectroscopy
Authors: Kheifets A. S. , Vos M. , Weigold E.
Published: August 2006

Electron momentum spectroscopy (EMS) gives direct information of the full energy-resolved electron momentum densities of occupied states (bands) in solids – single crystal, polycrystalline or amorphous. Here we present data from a new high energy EMS spectrometer using 50 keV incident and 25 keV outgoing electrons, on polycrystalline specimens of aluminium, copper and gold. The spectral momentum densities show very significant electron-electron correlation effects which are in good agreement with many-body Green´s function calculations.
Ultra-high Resolution Compton Scattering of Li Metal: Evaluation with Respect to the Correlation Corrected Occupation Number Density
Authors: Schülke W. , Sternemann C. , Kaprolat A. , Döring G.
Published: August 2006

Directional Compton profiles of Li metal measured with ultra-high momentum space resolution (0.02 a.u.) were analysed in terms of their reciprocal form factors
Electron Momentum Density Distribution in Cobalt Disilicide: Analysis by the Maximum Entropy Method
Authors: Bellin Ch. , Dobrzynski L. , Kouba H. , Loupias G. , Buslaps T. , Honkimäki V.
Published: August 2006

New cobalt disilicide high resolution Compton scattering measurements have been performed at ESRF (European Synchrotron radiation facility) in France. In a first step, experimental results are compared with calculated results, obtained from a self consistent linear muffin tin orbitals band structure calculations. The second step consists in studying three dimensional electron momentum density (EMD) distribution – 3D map – in CoSi
A Compton Scattering Study of Charge Transfer in Cr-Fe-Mn Alloys
Authors: Dobrzynski L. , Andrejczuk A. , Reniewicz H. , Szymanski K. , Zukowski E.
Published: August 2006

Compton profiles of polycrystalline Cr-Fe-Mn compounds were measured at room temperature using 60-keV gamma radiation from a
Investigations of Nuclear Quadrupole Interaction in BaMgAl10O17:Eu2+
Authors: Stephan M. , Schmidt P. C. , Mishra K. C. , Raukas M. , Ellens A. , Boolchand P.
Published: August 2006

Local environments of divalent europium ions in β-lattice of barium magnesium aluminate, BaMgAl
IR Multiple-Photon + UV Mutliphoton Laser Selective Fragmentation and Ionization of SF6 and CF2HCl Molecules
Authors: Lokhman V. N. , Ogurok D. D. , Ryabov E. A. , Letokhov V. S.
Published: August 2006

We have studied the formation mechanisms of the S