POLISH JOURNAL OF CHEMISTRY
Volume 71 Number 12 December 1997
Pages 1643- 1901


Special issue dedicated to Prof. B. Baranowski on the occasion of his 70th birtday


CONTENTS

Page

1643 Professor Bogdan Baranowski
— Filipek S.
REVIEW ARTICLES
1647 Two Applications of Pressure Tuning Spectroscopy to Characterize the Triplet States of
Organic Molecules and Complexes in Solid Media
— Drickamer H.G., Dreger Z.A.,
Lang J.M. and Yang G.
1661 Fundamental Importance of High Pressure Studies of the Palladium-Platinum-Hydrogen System
— Lewis F.A.
1668 Approaches to Description of the Pattern Formation in Electrochemical Systems with Finite Dimensions
— Nechiporuk V., Winkler I., Babiuk D. and Korzhik V.
IRREVERSIBLE PROCESSES
1680 Kinetics of Active Transport in Biological Membranes: Role of Barrier Fluctuations
— Fulinski A.
1699 Chaotic and Periodic Oscillations During Anodic Dissolution of Copper at Potentiostatic Conditions
— Dolata M. and Kawczynski A.L.
1707 Irreversible Thermodynamics of Transport Across Charged Membranes. A Comparative Treatment
— Narebska A. and Koter S.
1718 Thermodynamic Description of Translational Energy Relaxation in Binary Mixtures of Dilute Gases
— Cukrowski A.S., Fort J. and Fritzsche S.
HIGH PRESSURE PHYSICAL CHEMISTRY
1725 Lattice Rearrangements in Pd-Rich Alloys at Moderately High Temperatures and Pressures
— Flanagan T.B., Noh H. and Clewley J.
1735 High Pressure Studies of the FCC Chromium Hydride
— Tkacz M.
1742 Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC) at High Pressures: Investigations of a Liquid Crystal and a Triglyceride up to 300 MPa
— Schmidt C., Ernst C., Masberg S., Meyer-Inci C., Becker H. and Schneider G.M.
1749 Solvent Effects on the Kinetics and Diastereoselectivity of the Intermolecular Hetero Diels- -Alder Reaction of an Enamino Ketone with Isopropenyl Methyl Ether under High Pressure
— Tietze L.F., Henrich M., Rothert I., Kuchta G. and Buback M.
1763 p,T-Dependence of Self-Diffusion in the Fluid One Phase Region of the System Tetradecane/Methane
— Tarassov I.N., Wappmann S. and Luedemann H.-D.
1777 Thermoelectric Power of (NiMn)-H and (NiCo)-H Systems
— Filipek S.M.
GENERAL PHYSICAL CHEMISTRY
1787 Phase Diagram of the Thallium(I) Telluride-Copper(I) Telluride System
— Zaleska E., Gawel W., Sztuba Z. and Josiak J.
1792 The Inelastic Neutron Scattering Spectrum of dhcp Iron Hydride
— Cornell K., Wipf H., Antonov V.E., Antonova T.E., Kolesnikov A.I., Ponyatovsky E.G. and Dorner B.
1797 On the High Temperature Phase Transitions in Dihydrogen Phosphates
— Ortiz E., Vargas R.A., Mellander B.E. and Lunden A.
1803 Low Temperature Heat Capacity and Magnetic Measurements of Uranium 3d-Metal Hydrides
— Drulis M.
1809 On the Electroreduction of 3-Nitrophtalic Acid and Nitrobenzoic Acids in Aqueous Media
— Romanowski S., Stroka J. and Galus Z.
1821 The Influence of the Preceding Chemical Reaction upon the Hydrogen Electrode Reaction in Molten Ethylammonium Chloride
— Kisza A. and Wiecek B.
1831 Alkylsilanes and Alkylcarbosilanes as Single-Source Precursors for the Formation of a-Si:C:H Thin-Film Materials by Atomic Hydrogen-Induced Chemical Vapour Deposition
—Walkiewicz- -Pietrzykowska A., Wrobel A.M. and Kryszewski M.
1841 Complementarity Relations for the Extreme Changes of Electron Dynamical Observables in the Hydrogen Atom
— Olszewski S.
1852 Crystal Structure and Phase Transitions of the Ferroelectric Antimony Sulfoiodide SbSI. Part II. Crystal Structure of SbSI in Phases I, II and III
— Lukaszewicz K., Pietraszko A., Stepien-Damm J. and Kajokas A.
1858 Phase Diagrams of the Tl2Te-MxTey Systems
— Zaleska E., Gawel W. and Sztuba Z.
1863 Determination of Hydrogen Diffusion in Metals by the Electrochemical Current Pulse Time-lag Technique
— Zuechner H., Barlag H. and Opara L.
1875 ANNUAL INDEXES
1875  - CONTENTS
1875   -- Review Articles
1875   -- Inorganic Chemistry
1876   -- Organic Chemistry
1879   -- Physical Chemistry
1882   -- Crystal and Molecular Structures
1883   -- Communications
1884   -- Book Reviews and IUPAC Recommendations
1885   - AUTHOR INDEX
1893   - SUBJECT INDEX



ABSTRACTS


1647-1660

Two Applications of Pressure Tuning Spectroscopy
to Characterize the Triplet States of Organic
Molecules and Complexes in Solid Media

by H.G. Drickamer, Z.A. Dreger, J.M. Lang and G. Yang
School of Chemical Sciences, Dept. of Physics and Frederick Seitz Materials Research Laboratory,
University of Illinois at Champaign-Urbana, 600 S. Mathews St., Urbana, IL 61801-3792, USA

(Received April 7th, 1997)

Pressure tuning spectroscopy is a general and powerful tool for studying the effects of atomic or molecular interaction on electronic phenomena-broadly defined. In this paper we present a review of two studies of pressure effects on the triplet state of organic molecules in solid media.
In the first study we demonstrate the effect of compression on the photophysics and photochemistry of representative aromatic carbonyls. There are dramatic increases in phosphorescence and fluorescence efficiencies as well as strong perturbations on the reactivity.
In the second study we demonstrate the powerful effect of compression on inhibiting intracomplex motions of ligands for ruthenium organometallic complexes. This inhibition strongly effects the phosphorescence efficiency of the molecule.

1661-1667

Fundamental Importance of High Pressure Studies
of the Palladium-Platinum-Hydrogen System

by F.A. Lewis
School of Chemistry, The Queen's University of Belfast, Belfast BT9 5AG, Northern Ireland

(Received July 1st, 1997)

A short review is presented, which has been centred on results of measurements with a very extensive series of palladium/platinum alloys over a very wide range of hydrogen pressures extending up to 30 kbar (3 GPa). For the higher platinum content range of alloys, these studies have revealed that relationships at 25oC between hydrogen content (n = H/(Pd+Pt) atomic ratio) and incremental changes , of electrical resistivity, can be represented to a good approximation by a common curve of similar form to those of Nordheim types of relationship representative of resistivity-substitutional alloy composition relationships. Consideration of these interrelationships has led to interpretations (inclusive of hysteresis effects) of phase relationships of the palladium-hydrogen and lower platinum content regions of the palladium-platinum-hydrogen systems. Over the highest range of hydrogen pressures, values of hydrogen contents, n, have necessarily had to be derived from electrical resistivity measurements. Use, however, could have be made of correlating possibilities of interrelationships between , n and equilibrium hydrogen pressure, p, up to approximately 20 bar that are available from results of an allied series of electrode potential based experiments.

1668-1679

Approaches to Description of the Pattern Formation
in Electrochemical Systems with Finite Dimensions

by V. Nechiporuk, I. Winkler, D. Babiuk and V. Korzhik
Department of Physical Chemistry, Faculty of Chemistry, Chernovtsy State University,
Kotsybinsky Str., 2, Chernovtsy 274012, Ukraine

(Received June 27th, 1997; revised manuscript August 18th, 1997)

Some results regarding regularities of the Rayleigh-Benard type convection initiated in electrochemical systems both with finite or infinite electrodes are presented and gene-ralized. The influence of the electrolysis regime has also been taken into account. Similarity and distinction between convection in the electrochemical system with infinite electrodes and close phenomenon of the "pure" thermal convection initiation are commented. Break of the "continuous convective layer" is described for the electrochemical system with finite electrodes. The influence of lateral walls on the hydrodynamic stability of the electrolyte has been described. Region of regular convection occurrence has been drawn up on the parameter plane. A theoretical model, leading to a satisfactory agreement with experiment, has been proposed for the description of the bottom margin of the "convection area".

1680-1698

Kinetics of Active Transport in Biological Membranes: Role of Barrier Fluctuations

by A. Fulinski
M. Smoluchowski Institute of Physics, Jagiellonian University,
Reymonta 4, PL-30-059 Krakow, Poland
E-mail: fulinski@jetta.if.uj.edu.plhttp://zfs.if.uj.edu.pl

(Received February 11th, 1997; revised manuscript April 3rd, 1997)

The role of barrier fluctuations in the membrane enzymatic processes, among others in the active transport of ions through cell membranes is examined. Membrane electric potential plays the role of a barrier height (activation energy) for enzymes embedded in the cell membrane. This barrier height can be modulated either by internal fluctuations or by superimposed from without external electrical fields, either random or periodic. Measurements of the changes in reaction yield, or in ionic currents, governed by these enzymes (ionic pumps) can be used as tools for determining the parameters describing enzymatic action. Barrier fluctuations can change considerably the yield, including the inversion of the direction of transmembrane currents.

1699-1706

Chaotic and Periodic Oscillations During Anodic
Dissolution of Copper at Potentiostatic Conditions

by M. Dolata and A.L. Kawczynski
Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland

(Received June 4h, 1997; revised manuscript July 31st, 1997)

Transient periodic and chaotic oscillations observed during anodic dissolution of copper under potentiostatic conditions are described and analyzed.

1707-1717

Irreversible Thermodynamics of Transport Across Charged Membranes. A Comparative Treatment

by A. Narebska and S. Koter
Faculty of Chemistry, Nicolaus Copernicus University, 7 Gagarin Street, PL-87100 Torun, Poland (Received July 7th, 1997; revised manuscript September 8th, 1997)

A comparative examination of the friction coefficients, fik, coupling coefficients, qik, and mobility indices of water, RT/cwrww, for the cation-exchange membranes, published from different laboratories, is presented. The counterion-coion-water and membrane network interactions have been discussed and general conclusions about the interrelat-
ions of the membrane morphology and properties have been drawn.

1718-1724

Thermodynamic Description of Translational Energy
Relaxation in Binary Mixtures of Dilute Gases

by A.S. Cukrowski1,2 , J. Fort3 and S. Fritzsche4
1Institute of Physical Chemistry, Polish Academy of Sciences,
ul. Kasprzaka 44/52, 01-224 Warsaw, Poland
2Pedagogical University, Faculty of Mathematical and Natural Sciences,
Institute of Chemistry, ul. Checinska 5, 25-020 Kielce, Poland
3Seccio de Fisica, Departament d'Enginyeria Industrial, Escola Politecnica Superior,
Universitat de Girona, Avda Lluis Santalo s/n, 17071 Girona, Catalonia, Spain
4Leipzig University, Faculty of Physics and Geosciences, Institute of Theoretical Physics,
Augustusplatz 9-11, D-04109 Leipzig, Germany

(Received July 3rd, 1997; revised manuscript September 11th, 1997)

An expression relating the phenomenological coefficient L to the relaxation time tau and temperatures is derived within the formalism of non-equilibrium thermodynamics. For the model of hard spheres the coefficient L is expressed by number densities of components, the molecular masses, the diameters of spheres, the correlation function and temperatures. The values of tau and L are calculated for binary mixtures of noble gases. It is shown that L (similarly to tau) is time dependent, because the temperatures of components change during the relaxation process. Such changes are smaller than 10 percent even for relatively large temperature differences.

1725-1734

Lattice Rearrangements in Pd-Rich Alloys at
Moderately High Temperatures and Pressures

by T.B. Flanagan, H. Noh and J. Clewley
Department of Chemistry, University of Vermont, Burlington VT, 05405, USA
E-mail: flanagan@emba.uvm.edu

(Received June 5th, 1997)

Research on the hydrogen solubilities in three different forms of Pd3Mn are reviewed. These are the two ordered forms: L12, long-period superstructure (Al3Zr-type), and the disordered form. Similar to the hydrogen solubilities in Pd3Fe, studied earlier in Baranowski's laboratory, the ordered forms of Pd3Mn dissolve significantly more hydrogen than its disordered form. Dissolved H induces metal atom diffusion so that the disordered form of Pd3Mn orders at significantly lower temperatures than in vacuo. It orders in the presence of dissolved H to the L12 rather than the long-period superstructure (lps) form, which results from annealing in vacuo.
In the alloy system Pd-Rh, dissolved H is shown to enhance metal atom diffusion leading to phase separation in accord with the miscibility gap phase diagram. In the case of Pd-Pt alloys dissolved H can lead to phase separation via a ternary equilibrium; dissolved H is shown to enhance metal atom diffusion in this system.

1735-1741

High Pressure Studies of the FCC Chromium Hydride

by M. Tkacz
Institute of Physical Chemistry, Polish Academy of Sciences,
Kasprzaka 44/52, 01-224 Warsaw, Poland

(Received June 23rd, 1997)

The equilibrium pressure of hydrogen gas above solid face centered cubic (fcc) phase of chromium hydride has been determined at 150oC. As compared to the hexagonal close packed (hcp), chromium hydride plateau for the alpha + ß phase region has been found to be lower by about 500 bars and equal to 0.25 +/- 0.01 GPa. As a consequence, lower value of standard free energy of formation of the fcc chromium hydride has been calculated and a lower equilibrium pressure at normal temperature as well. One can also assume a lower hydrogen pressure necessary for a direct synthesis of the fcc hydride, as compared to the hcp phase. The search for possible pressure induced phase transition from the fcc to the hcp structure has been unsuccessful up to 37 GPa. The compressibility of the fcc hydride is similar to that of the hcp phase, showing pressure independence of the hydrogen volume in the metal lattice, and confirming the general rule observed in transition metal hydrides.

1742-1748

Differential Thermal Analysis (DTA) and Differential
Scanning Calorimetry (DSC) at High Pressures:
Investigations of a Liquid Crystal
and a Triglyceride up to 300 MPa

by C. Schmidt, C. Ernst, S. Masberg, C. Meyer-Inci,
H. Becker and G.M. Schneider
Ruhr-Universitaet Bochum, Lehrstuhl fuer Physikalische Chemie II, D-44780 Bochum, Germany
E-mail: gerhard.schneider@ruhr-uni-bochum.de

(Received July 3rd, 1997)

In this paper high-pressure differential thermal analysis (DTA) and differential scanning calorimetry (DSC) measurements up to 300 MPa are presented on a selected liquid crystal (4-n-decyloxy-4'-cyanobiphenyl, 10OCB) and triglyceride (1,2,3-tris-eicosano-yloxypropane, Triarachidin, AAA), respectively. In particular T(p) phase equilibrium data are given as well as transition enthalpy values as a function of pressure along the transition lines. For 10OCB a stable pressure-induced nematic phase has been detected at pressures above 34 MPa; for this substance the T(p) phase diagram was also determined by high-pressure polarization microscopy. For pure AAA a metastable phase is found at low pressures that transforms to the stable ß modification with increasing temperatures; at higher pressures only the melting of a solid phase could be detected, whereas for the substance saturated with helium both transitions could be observed in the whole experimental pressure range up to about 100 MPa by DTA and 200 MPa by DSC.

1749-1762

Solvent Effects on the Kinetics and Diastereoselectivity
of the Intermolecular Hetero Diels-Alder Reaction
of an Enamino Ketone with Isopropenyl
Methyl Ether under High Pressure

by L.F. Tietze1, M. Henrich1, I. Rothert1, G. Kuchta2 and M. Buback2
1Institut fuer Organische Chemie der Universitaet Goettingen,
Tammannstrasse 2, D-37077 Goettingen, Germany
2Institut fuer Physikalische Chemie der Universitaet Goettingen,
Tammannstrasse 6, D-37077 Goettingen, Germany

(Received July 14th, 1997)

The intermolecular hetero Diels-Alder reaction of enamino ketone 1 with isopropenyl methyl ether 2 leading to the diastereomeric products 3 and 4 is studied under high pressure up to 5 kbar and at temperatures between 30oC and 120oC. The kinetics are measured by on-line FT-IR spectroscopy up to 3 kbar. The ratio of the diastereomeric products is determined by HPLC-analysis. In order to gauge the influence of solvent properties on the kinetics and diastereoselectivity, the cycloaddition is carried out in dichloromethane, in acetonitrile and in a mixture of heptane/isodurene (2:1). Clear effects of solvent polarity on the rate coefficients as well as on the activation parameters are observed. To quantify the solvent influence on the activation volume, an estimate of the intrinsic (solvent-independent) contribution to the activation volume, V intr, is made

1763-1776

p,T-Dependence of Self-Diffusion in the Fluid
One Phase Region of the System Tetradecane/Methane

by I.N. Tarassov, S. Wappmann and H.-D. L<129>demann
University of Regensburg, Institute of Biophysics and Biophysical Chemistry, D-93040 Regensburg, Germany

(Received July 1st, 1997; revised manuscript August 11th, 1997)

High pressure self-diffusion coefficients and densities are reported for the binary system tetradecane/methane in a wide range of temperature at pressures up to 200 MPa. The experimental diffusion data of these mixtures are analyzed in the frame work of the rough hard sphere (RHS) model under application of hard sphere (HS) molecular dynamics simulations for binary mixtures of hard spheres obtained recently in our group. The rotation-translation coupling parameter A shows a weak temperature dependence, falling slightly when the temperature is lowered. The RHS-diameter for the lighter compound is identical to the value found for neat methane. The value for the RHS-diameter of tetradecane in the mixture is found slightly larger than in the neat tetradecane. Both diameter show a slight increase with falling temperature..

1777-1786

Thermoelectric Power of (NiMn)-H and
(NiCo)-H Systems

by S.M. Filipek
Institute of Physical Chemistry of the Polish Academy of Sciences,
ul. Kasprzaka 44, 01-224 Warsaw, Poland

(Received August 13th, 1997)

Thermoelectric power of Ni95Co5, Ni90Co10 and Ni90.7Mn9.3, Ni82.5Mn17.5 alloys was measured as a function of hydrogen pressure up to 1.7 GPa for nickel-cobalt and up to 1.0 GPa for nickel-manganese alloys. For the last alloys the change of thermopower during the hydride formation is positive and approaches the value characteristic for pure copper. The behavior of nickel-cobalt alloys was, unexpectedly, different from that of all other nickel alloys investigated so far. When 5 at.% of cobalt is dissolved in nickel the hydride forms at 25oC almost without change of thermopower. When the concentrat-
ion of cobalt increases to 10 at.% the hydride formation is accompanied by a large negative change of thermopower. A qualitative interpretation is proposed.

1787-1791

Phase Diagram of the Thallium(I)
Telluride-Copper(I) Telluride System

by E. Zaleska1, W. Gawel2, Z. Sztuba1 and J. Josiak2
1Department of Analytical Chemistry,
2Department of Inorganic Chemistry, University of Medicine, Szewska 38, 50-139 Wroclaw, Poland

(Received April 1st, 1997; revised manuscript June 2nd, 1997)

The phase diagram of the Tl2Te-Cu2Te system has been established by thermal analysis (cooling curve method) and differential thermal analysis. The results obtained are compared with those of electrochemical studies on the same system. In the system three compounds are formed (CuTl9Te5, Cu6Tl4Te5 and Cu9TlTe5).

1792-1796

The Inelastic Neutron Scattering Spectrum of
dhcp Iron Hydride

by K. Cornell1, H. Wipf1, V.E. Antonov2, T.E. Antonova2,
A.I. Kolesnikov2, E.G. Ponyatovsky2 and B. Dorner3
1Institut fuer Festkoerperphysik, Technische Hochschule Darmstadt,
Hochschulstrasse 6, D-64289 Darmstadt, Germany
2Institute of Solid State Physics, Russian Academy of Sciences,
142432 Chernogolovka, Moscow district, Russia
3Institute Laue-Langevin, B.P. 156, F-38042 Grenoble Cedex 9, France

(Received July 2nd, 1997)

The optic phonon modes of hydrogen in dhcp iron hydride (FeHx with x close to 1) were investigated by neutron spectroscopy. The optic phonons have energies between ~70 and ~140 meV. The average energy of the optic phonons is ~105 meV.

1797-1802

On the High Temperature Phase Transitions
in Dihydrogen Phosphates

by E. Ortiz2, R.A. Vargas3, B.E. Mellander1 and A. Lunden1
1Physics and Engineering Physics, Chalmers University of Technology and Goeteborg University,
S-412 96 Goeteborg, Sweden 2Departamento de Fisica, Universidad del Atlantico, A.A.1890, Barranquilla, Colombia 3Departamento de Fisica, Universidad del Valle, A.A. 25360, Cali, Colombia

(Received July 3rd, 1997)

Thermal analysis and X-ray diffraction were used to study both the dynamic process of dehydration and the high-temperature phase transition at Tp in KH2PO4 and RbH2PO4. Our results show strong evidence that at Tp an onset of partial polymerization takes place rather than a polymorphic phase transition.

1803-1808

Low Temperature Heat Capacity and Magnetic
Measurements of Uranium 3d-Metal Hydrides

by M. Drulis
W. Trzebiatowski Institute for Low Temperature and Structure Research, Polish Academy of Sciences,
P.O.Box 937, 50-950 Wroclaw 2, Poland

(Received July 14th, 1997)

Specific heats and magnetic properties as a function of temperature and magnetic field for U6MH17 (M = Fe, Co, Mn and Ni) hydrides have been measured. These hydrides crystallize in the cubic Pm3n space group, like ß-UH3. The compounds are ferromagnets. The essential thermodynamic functions of the entropy S and energy E for magnetic heat contribution were evaluated. It was established, that 3d-metals change the magnitude of the magnetic anisotropy having, however a negligible influence on the magnetic transition temperature. The spin-reorientation transitions, suggested previously, were not confirmed.

1809-1820

On the Electroreduction of 3-Nitrophtalic Acid
and Nitrobenzoic Acids in Aqueous Media

by S. Romanowski1, J. Stroka2 and Z. Galus2
1University of Lodz, Department of Theoretical Chemistry, Pomorska 149/53, 90-236 Lodz, Poland
2University of Warsaw, Department of Chemistry, Pasteura 1, 02-093 Warsaw, Poland

(Received July 14th, 1997)

The electrochemical behaviour of 3-nitrophtalic (3-NPA) and nitrobenzoic acids on mercury electrodes has been investigated. By using chronovoltammetry and chronocoulometry with pulse time ranging from 4 to 100 msec, it was found that above pH 8 in the case of 3-nitrophtalic acid anion one 4-electron wave separates into 1-electron and 3-electron wave. Such behaviour was not observed in other nitrobenzene derivatives such as nitrobenzoic acids. The influence of pH, pulse time, reactant concentration and Lewis acids on the 3-NPA wave separation has been studied. Semi-empirical calculations of charge distribution for 3-NPA, nitrobenzoic acids and nitrobenzene, as well as their free radicals and dianions, have shown significantly higher electron density on nitro group of 3-NPA radical than on other species studied. This difference in electron density distribution may generate the non-typical electrochemical behaviour of 3-nitrophtalic acid.

1821-1830

The Influence of the Preceding Chemical Reaction
upon the Hydrogen Electrode Reaction in Molten
Ethylammonium Chloride

by A. Kisza and B. Wiecek
Faculty of Chemistry, University of Wroclaw, 50383 Wroclaw, Poland

(Received June 3rd, 1997; revised manuscript July 21st, 1997)

The impedance spectra of the hydrogen electrode reaction (HER) as a function of potential at several temperatures in pure molten ethylammonium chloride (EACl) were recorded. The recorded impedance spectra were worked out using an equivalent circuit approach and the theory of impedance of a quasi reversible electrode process preceded by a chemical (dissociation) reaction. This allows for the determination of the exchange current density, its activation energy, diffusion coefficient of the hydrogen cation and the forward and backward rate constants of the preceding dissociation of the ethylammonium cation.

1831-1840

Alkylsilanes and Alkylcarbosilanes as Single-Source
Precursors for the Formation of a-Si:C:H Thin-Film
Materials by Atomic Hydrogen-Induced Chemical
Vapour Deposition

by A. Walkiewicz-Pietrzykowska, A.M. Wrobel and M. Kryszewski
Polish Academy of Sciences, Centre of Molecular and Macromolecular Studies,
Sienkiewicza 112, 90-363 Lodz, Poland

(Received June 3rd 1997; revised manuscript August 1st, 1997)

A number of alkylsilanes and alkylcarbosilanes of widely different molecular structure are characterized in terms of their ability to the formation of amorphous hydrogenated silicon-carbon (a-Si:C:H) film in atomic hydrogen-induced chemical vapour deposition (AHCVD). The compounds, containing only the Si-C bonds or four-membered carbosilane rings appear to be inactive, while those with the Si-Si or Si-H bonds are capable of the a-Si:C:H film-formation. The reactivity of the latter group of compounds in the AHCVD is characterized by the deposition yield parameter, determined at constant and variable feeding rates. Basing upon the reactivity data, the mechanism of the initiation step is proposed.

1841-1851

Complementarity Relations for the Extreme Changes of Electron Dynamical Observables
in the Hydrogen Atom

by S. Olszewski
Institute of Physical Chemistry of the Polish Academy of Sciences,
Kasprzaka 44/52, 01-224 Warsaw, Poland

(Received June 20th, 1997; revised manuscript August 4th, 1997)

Extreme changes of electron dynamical observables in the hydrogen atom are examined. It is found that these changes calculated for the fundamental electron observables (position, momentum, time period and energy) can be combined into products whose values are not much different than the Planck constant h. A similar property is demonstrated for the rotation angle and orbital angular momentum of an electron enclosed in a spherical cavity. Extreme changes calculated for the observables being a function of electron position and momentum can be also combined into products, which are formally similar to expressions obtained for the commutators of the observables.

1852-1857

Crystal Structure and Phase Transitions of the
Ferroelectric Antimony Sulfoiodide SbSI. Part II.
Crystal Structure of SbSI in Phases I, II and III

by K. Lukaszewicz1, A. Pietraszko1, J. Stepien-Damm1 and A. Kajokas2
1Institute of Low Temperature and Structure Research, Polish Academy of Sciences,
Okolna 2, 50-950 Wroclaw, Poland, E-mail: KL@highscreen.int.pan.wroc.pl
2Department of Physics, University of Vilnius, Sauletekio al. 9/3, 2054 Vilnius, Lithuania

(Received June 26th, 1997; revised manuscript August 8th, 1997)

Crystal structure of antimony sulfoiodide SbSI has been determined in all three phases: ferroelectric, antiferroelectric and paraelectric. In the ferroelectric phase III crystals of SbSI are polar in the space group Pna21 in agreement with previous reports. Above the Curie point at 298 K SbSI in phase II becomes antiferroelectric in the space group P212121 and alternating arrangement of polar double chains parallel to [001]. Only above the high temperature phase transition at 410 K, the crystals of SbSI become centrosymmetric in the space group Pnam.

1858-1862

Phase Diagrams of the Tl2Te-MxTey Systems

by E. Zaleska, W. Gawel1 and Z. Sztuba
Department of Analytical Chemistry, Department of Inorganic Chemistry 1,
Wroclaw University of Medicine, 50-139 Wroclaw, ul. Szewska 38, Poland

(Received July 2nd, 1997; revised manuscript September 10th, 1997)

Results of phase studies of Tl2Te-MxTey systems are presented, obtained by DTA, TA, concentration cell EMF and X-ray diffraction methods. Factors influencing the formation of ternary compounds are discussed.

1863-1875

Determination of Hydrogen Diffusion in Metals by the
Electrochemical Current Pulse Time-lag Technique

by H. Zuechner, H. Barlag and L. Opara
Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet, D-48149 Muenster, Germany

(Received August 12th, 1997; revised manuscript September 16th, 1997)

Correct diffusion measurements using electrochemical time-lag methods must be carried out under careful consideration of the experimental boundary conditions. Additionally, the interpretation of the measured data requires an exact knowledge of the sample composition, structure and the hydrogen concentration.
Considering these basic requirements, the current pulse technique yields reliable data for the hydrogen diffusion in metals and alloys with high solubilities, from extremely low to high hydrogen concentrations, as well as with low solubilities. This is mainly demonstrated on measurements on the PdxAg1-x system.

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