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Resonant modes due to anion interstitials and anion vacancies in fluorites
Solid State Communications, Vol. 35, pp. i—viii. Pergamon Press Ltd. 1980. Printed in Great Britain.
Abstracts of Articles to be Published in The Journal of Physics and Chemistry of Solids J Phys. Chem. Solids (to be published)’ should be cited in references to material quoted from this section prior to the publication of the relevant article. 1.
fixed at 0.80 ±0.07. Estimates of dispersion
PREFERENTIAL ORDERING OF Mn and Fe ATOMS IN Y6(Fe1_~Mn~)23
corrections to the X-ray scattering factors for iron near the Fe K edge were obtained through observations of SR diffraction from a magnetite crystal. Results do not differ appreciably from predicted values in the range 6358—7105 eV, though the precision in estimates of the imaginary term is poor at the lower energies. Received 24 January 1980
WJ. James, Department of Chemistry and Graduate Center for Materials Research, University of Missouri Rolla, Rolla, MO 65401, U.S.A.; and W. B. Yelon, Department of Physics and Missouri University Research Reactor, University of Missouri Columbia, Columbia, MO 65201, U.S.A. —
—
3.
Neutron diffraction studies of the nonmagnetic compositional range of the Y6(Fe1_~Mn~)23 system reveal the presence of preferential ordering of Fe and Mn atoms on the four transition metal crystallographic sites. Throughout the entire compositional range of the ternary system, Mn atoms prefer to occupy the f2 site and Fe atoms thef1 site. Refinements of the data were carried out using the Rietveld profile method.
LOW TEMPERATURE THERMAL CONDUCTIVITY OF 0H AND 0D DOPED LIF SINGLE CRYSTALS
Kurt Guckelsberger, Centre d’Etudes Nucléaires de Grenoble, Department de Transfert et Conversion d.Energie, Service Basses Temperatures, 85 X, F-38041 Grenoble Cedex, France. Thermal conductivity measurements between 0.1 and 70K of OH and OW doped [IF indicates resonant phonon scattering at 0.86 cm’ for 0H’ and 0.43 cm for OW. Hydroxyl impurities
Received 12 November 1979 Revised 19 March 1980
‘
2.
DETERMINATION OF THE CATION SITEOCCUPATION PARAMETER IN A COBALT FERRITE FROM SYNCHROTRONRADIATION DIFFRACTION DATA H.L. Yakel, Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, TN 37830, U.S.A.
trapped at divalent impurity sites do not scatter phonons resonantly and it is shown that inhomogenous distribution of strong scattering centers modify thermal conductivity curves considerably. A simple tunneling model for the isotope shift suggests an effect similar to the “polaron” model of paraelastic centers. A relaxation time for phonon scattering by
Energy-tuned synchrotron radiation (SR) was used to collect Bragg diffraction intensity data from a single crystal of a cobalt ferrite (nominally Co Fe204). X-ray energies were chosenjust below the Fe and Co K absorption edges where large changes in anomalous dispersion enhance differences in scattering between the two metals. Observations were analyzed by leastsquares methods to determine the value of the parameter,X, that describes the distribution of cobalt and iron ions on the octahedral and tetrahedral sites of the cubic spine! structure. Refinements based on over 290 SR data gave X = 0.83 ±0,01 (83% of the cobalt ions located on octahedral sites). with only 30 specially selected SR data, this value could be
OW is derived, showing that the ground state may be understood in terms of a direct process, underlining that this system provides a connection between the theory of paraelectric/paraelastic impurities and Jahn—Teller systems. Received 26 September 1979 Revised 14 March 1980 4.
RESONANT MODES DUE TO ANION INTERSTITIALS AND ANION VACANCIES IN FLUORITES M.A.H. Nerenberg, T.M. Haridasan, J. Govindarjan and P.W.M. Jacobs, University of
i
ii
ABSTRACTS OF ARTICLES TO BE PUBLISHED IN J. PHYS. CHEM. SOLIDS Western Ontario, London, Ontario N6A 5B7, Canada.
The resonant modes due to anion interstitials and anion vacancies in fluorites are computed on the basis of a Green’s function formalism. The Green’s functions are calculated on the basis of shell model fitted to the phonon dispersion curves of the respective crystals. The force constant changes are claculated by finding the relaxations of the different host atoms and then using the short range potential due to Catlow and Norgett. The calculated frequencies of the resonant mode due to anion interstitials in BaF 2 shows good agreement with the experimental results. The results are discussed in a comparative fashion for the three crystals CaF 2, SrF2 and BaF2 along with the possibility of their experimental detection. Received 13 August 1979 Revised 14 March 1980 5.
A NEUTRON DIFFRACTION STUDY OF H, Na—Y ZEOLITES Z. Jir~lk,Institute of Physics, Czech. Acad. Sci., Na Slovance 2, 18040 Praha 8, Czechoslovakia; S. Vratislav, Faculty of Nuclear Physics and Physical Engineering, Bfehov~7, 115 19 Praha 1, Czechoslovakia; and V. Bos~ek,The J. Heyrovsk~Institute of Physical Chemistry and Electrochemistry, Czech. Acad. Sci., M~chova7, 121 38 Praha 2, Czechoslovakia.
A series of Y-zeolites with different degrees of decationization has been studied by means of the neutron powder diffraction techniquein order to determine the distribution of cations and protons over various sites in the zeolite structure. The protons were found to form structural OH groups with the framework oxygen atoms. The observed occupancies of the proton sites are in agreement with conclusions based upon other methods. Received 1 August 1979 Revised 29 February 1980 6.
HEAT CAPACITY AND PHASE TRANSITION OF A FIVE-COORDiNATED ANTIFERROMAGNET, IODOBIS (N, N-DIEHTYLIDTHIOCARBAMATO) IRON(III), IN THE TEMPERATURE RANGE FROM 0.4 to 300K Masanori Yoshikawa, Michio Sorai, Hiroshi Suga and SyilzO Seki, Department of Chemistry, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan.
The heat capacity of iodobis (N, N-diethyldithiocarbamoto) iron(III) has been measured between 0.4 and
Vol. 35, No.4
300 K. A phase transition from an antiferromagnetic to a paramagnetic state was found at TN = 1.937 ±0.010K. and a Schottky-type anomaly arising from a zero-field single ion splitting was observed around 12 K. The total magnetic entropy and enthalpy, including the phase transition and the Schottky-type anomaly, are 11.36 JK1 moF1 and 134.5 J mol~ respectively. The entropy is approximately equal to R in 4( 11.53 JK’ moF1), confirming that the spin manifold is really a quartet. The entropy and enthalpy due to the phase transition are estimated 1 moF1 and (13.2 ±0.05) to be (5.57 ±0.01)JK JmoF1 respectively. The entropy and enthalpy ,
,
above TN are quite large, as in the case of the related compound chlorobis (N, N-diethyldithiocarbamato) iron(II1). This fact suggests that the present complex may be considered to have a two-dimensional type of magnetic structure from a thermodynamic point of view. A correlation diagram between the transition entropy and energy is proposed, this being a diagnostic for the determination of the magnetic dimensionality. Received 30 August 1979 Revised 19 March 1980 PRISE EN COMPTE DES CORRELATIONS DI~LECTRONIQUESDANS LES PETITS AMAS PAR LA M~THODEDE GUTZWILLER P. Joyes and S. Ortoli, [.aboratoire de Physique des Solids associé au CNRS, Université Paris-Sud 91405 Orsay, France. We apply a variational Gutzwiler method to the analysis of the influence of the electronic correlations on small aggregates properties. We first describe the general method then we check it by comparison to the results given by an “exact” solution of the Hubbard Hamiltonian for 4 or 5 atoms. We also examine the behaviour of the cluster stabilities when the number of atoms varies. One knows that, for U = 0, the stablest ions have an odd number of atoms but that this property disappears when U = o°. We obtain here, as expected, an intermediate result. Received 7 January 1980
8.
GROUND STATE PROPERTIES OF CsCoCl3 W.B. Euler and B.B. Garrett, Department of Chemistry, Florida State University, Tallahassee, FL 32306, U.S.A. The electronic spectra of CsCoCl3 are fit to a Hamiltonian that includes terms for interelectton repulsion, octahedral and trigonal crystal fields, and
Abstracts of Articles to be Published in The Journal of Physics and Chemistry of Solids J Phys. Chem. Solids (to be published)’ should be cited in references to material quoted from this section prior to the publication of the relevant article. 1.
fixed at 0.80 ±0.07. Estimates of dispersion
PREFERENTIAL ORDERING OF Mn and Fe ATOMS IN Y6(Fe1_~Mn~)23
corrections to the X-ray scattering factors for iron near the Fe K edge were obtained through observations of SR diffraction from a magnetite crystal. Results do not differ appreciably from predicted values in the range 6358—7105 eV, though the precision in estimates of the imaginary term is poor at the lower energies. Received 24 January 1980
WJ. James, Department of Chemistry and Graduate Center for Materials Research, University of Missouri Rolla, Rolla, MO 65401, U.S.A.; and W. B. Yelon, Department of Physics and Missouri University Research Reactor, University of Missouri Columbia, Columbia, MO 65201, U.S.A. —
—
3.
Neutron diffraction studies of the nonmagnetic compositional range of the Y6(Fe1_~Mn~)23 system reveal the presence of preferential ordering of Fe and Mn atoms on the four transition metal crystallographic sites. Throughout the entire compositional range of the ternary system, Mn atoms prefer to occupy the f2 site and Fe atoms thef1 site. Refinements of the data were carried out using the Rietveld profile method.
LOW TEMPERATURE THERMAL CONDUCTIVITY OF 0H AND 0D DOPED LIF SINGLE CRYSTALS
Kurt Guckelsberger, Centre d’Etudes Nucléaires de Grenoble, Department de Transfert et Conversion d.Energie, Service Basses Temperatures, 85 X, F-38041 Grenoble Cedex, France. Thermal conductivity measurements between 0.1 and 70K of OH and OW doped [IF indicates resonant phonon scattering at 0.86 cm’ for 0H’ and 0.43 cm for OW. Hydroxyl impurities
Received 12 November 1979 Revised 19 March 1980
‘
2.
DETERMINATION OF THE CATION SITEOCCUPATION PARAMETER IN A COBALT FERRITE FROM SYNCHROTRONRADIATION DIFFRACTION DATA H.L. Yakel, Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, TN 37830, U.S.A.
trapped at divalent impurity sites do not scatter phonons resonantly and it is shown that inhomogenous distribution of strong scattering centers modify thermal conductivity curves considerably. A simple tunneling model for the isotope shift suggests an effect similar to the “polaron” model of paraelastic centers. A relaxation time for phonon scattering by
Energy-tuned synchrotron radiation (SR) was used to collect Bragg diffraction intensity data from a single crystal of a cobalt ferrite (nominally Co Fe204). X-ray energies were chosenjust below the Fe and Co K absorption edges where large changes in anomalous dispersion enhance differences in scattering between the two metals. Observations were analyzed by leastsquares methods to determine the value of the parameter,X, that describes the distribution of cobalt and iron ions on the octahedral and tetrahedral sites of the cubic spine! structure. Refinements based on over 290 SR data gave X = 0.83 ±0,01 (83% of the cobalt ions located on octahedral sites). with only 30 specially selected SR data, this value could be
OW is derived, showing that the ground state may be understood in terms of a direct process, underlining that this system provides a connection between the theory of paraelectric/paraelastic impurities and Jahn—Teller systems. Received 26 September 1979 Revised 14 March 1980 4.
RESONANT MODES DUE TO ANION INTERSTITIALS AND ANION VACANCIES IN FLUORITES M.A.H. Nerenberg, T.M. Haridasan, J. Govindarjan and P.W.M. Jacobs, University of
i
ii
ABSTRACTS OF ARTICLES TO BE PUBLISHED IN J. PHYS. CHEM. SOLIDS Western Ontario, London, Ontario N6A 5B7, Canada.
The resonant modes due to anion interstitials and anion vacancies in fluorites are computed on the basis of a Green’s function formalism. The Green’s functions are calculated on the basis of shell model fitted to the phonon dispersion curves of the respective crystals. The force constant changes are claculated by finding the relaxations of the different host atoms and then using the short range potential due to Catlow and Norgett. The calculated frequencies of the resonant mode due to anion interstitials in BaF 2 shows good agreement with the experimental results. The results are discussed in a comparative fashion for the three crystals CaF 2, SrF2 and BaF2 along with the possibility of their experimental detection. Received 13 August 1979 Revised 14 March 1980 5.
A NEUTRON DIFFRACTION STUDY OF H, Na—Y ZEOLITES Z. Jir~lk,Institute of Physics, Czech. Acad. Sci., Na Slovance 2, 18040 Praha 8, Czechoslovakia; S. Vratislav, Faculty of Nuclear Physics and Physical Engineering, Bfehov~7, 115 19 Praha 1, Czechoslovakia; and V. Bos~ek,The J. Heyrovsk~Institute of Physical Chemistry and Electrochemistry, Czech. Acad. Sci., M~chova7, 121 38 Praha 2, Czechoslovakia.
A series of Y-zeolites with different degrees of decationization has been studied by means of the neutron powder diffraction techniquein order to determine the distribution of cations and protons over various sites in the zeolite structure. The protons were found to form structural OH groups with the framework oxygen atoms. The observed occupancies of the proton sites are in agreement with conclusions based upon other methods. Received 1 August 1979 Revised 29 February 1980 6.
HEAT CAPACITY AND PHASE TRANSITION OF A FIVE-COORDiNATED ANTIFERROMAGNET, IODOBIS (N, N-DIEHTYLIDTHIOCARBAMATO) IRON(III), IN THE TEMPERATURE RANGE FROM 0.4 to 300K Masanori Yoshikawa, Michio Sorai, Hiroshi Suga and SyilzO Seki, Department of Chemistry, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan.
The heat capacity of iodobis (N, N-diethyldithiocarbamoto) iron(III) has been measured between 0.4 and
Vol. 35, No.4
300 K. A phase transition from an antiferromagnetic to a paramagnetic state was found at TN = 1.937 ±0.010K. and a Schottky-type anomaly arising from a zero-field single ion splitting was observed around 12 K. The total magnetic entropy and enthalpy, including the phase transition and the Schottky-type anomaly, are 11.36 JK1 moF1 and 134.5 J mol~ respectively. The entropy is approximately equal to R in 4( 11.53 JK’ moF1), confirming that the spin manifold is really a quartet. The entropy and enthalpy due to the phase transition are estimated 1 moF1 and (13.2 ±0.05) to be (5.57 ±0.01)JK JmoF1 respectively. The entropy and enthalpy ,
,
above TN are quite large, as in the case of the related compound chlorobis (N, N-diethyldithiocarbamato) iron(II1). This fact suggests that the present complex may be considered to have a two-dimensional type of magnetic structure from a thermodynamic point of view. A correlation diagram between the transition entropy and energy is proposed, this being a diagnostic for the determination of the magnetic dimensionality. Received 30 August 1979 Revised 19 March 1980 PRISE EN COMPTE DES CORRELATIONS DI~LECTRONIQUESDANS LES PETITS AMAS PAR LA M~THODEDE GUTZWILLER P. Joyes and S. Ortoli, [.aboratoire de Physique des Solids associé au CNRS, Université Paris-Sud 91405 Orsay, France. We apply a variational Gutzwiler method to the analysis of the influence of the electronic correlations on small aggregates properties. We first describe the general method then we check it by comparison to the results given by an “exact” solution of the Hubbard Hamiltonian for 4 or 5 atoms. We also examine the behaviour of the cluster stabilities when the number of atoms varies. One knows that, for U = 0, the stablest ions have an odd number of atoms but that this property disappears when U = o°. We obtain here, as expected, an intermediate result. Received 7 January 1980
8.
GROUND STATE PROPERTIES OF CsCoCl3 W.B. Euler and B.B. Garrett, Department of Chemistry, Florida State University, Tallahassee, FL 32306, U.S.A. The electronic spectra of CsCoCl3 are fit to a Hamiltonian that includes terms for interelectton repulsion, octahedral and trigonal crystal fields, and