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Electron spin resonance investigation of the structural phase transitions in Al urea6(ClO4)3 and Ga urea6(ClO4)3
iv
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
nitrogen centre previously reported, characterised by a 14N) = 7.5 G and A 4N) = hyperfine 11( 1(’ 5.0 G. Thistriplet centrewithA was accompanied by the common nitrogen centre in only one case. Other naturally occurring centres, apparently comprising two weakly coupled electrons in triplet states, were too poorly defmed to characterise fully. Received 19 May 1975 Revised 6August 1976 5
SELENIUM CRYSTALLIZATION INDUCED BY COROTRON CHARGING H.W. Pinsler and W.E. Brower, Xerox Corporation, Webster, NY 14580, U.S.A.
ur6(C104)3 and Ga ur6(C1O4)3 with T~= 300 K are studied by means of ESR on single crystals doped with the analogous Cr(III) compound. The transitions are antiferrodistortive and of the displacive type, the displacements resulting from the condensa.tion of aX 2 mode [k = (0 ~ ~)1of the dO4 ions. The ESR parameters have the same temperature dependence as the order parameters and can be described byD and E lØ~.The space group describing the structure changes from S~to S~,and the number of domains is multiplied by three. Above 300 K the crystals already consist of two domains, resulting from a ferrodistortive phase transition D~d S The actual transition temperature ofthe latter phase transition lies at some temperature above the decomposition temperature of the crystals. -~
Amorphous selenium films were exposed to corotron charging and simultaneous photo discharging. Corotron charging increased considerably the rate of crystal8 lization compared to photocrystaffization. This increase was manifested as a higher top surface nucleation rate m the corotron charged regions. An ion recombination mechanism is proposed to explain the enhanced crystallization due to corotron charging. • Received 4May 1976 • Revised 6 August 1976 6
PROPERTIES SUGGESTING H-TYPE CLUSTERS IN SOME METALLIC HYDRIDES D. Lupu and R.V. Bucur, Institute of Stable Isotopes, Cluj-Napoca, P.O. Box 243, Str. Donath 65-103, Romania.
The p—c—-T relationships for the hydrogen-rich phase of some metallic hydrides are calculated supposing the formation of H-type clusters in the metal lattice in equilibrium with the hydrogen gas. The experimental data for the hydride phase of LaNi5, Pd, Nb(HINb ~ 0.75) and U are consistent with this model. Other properties in literature which seem to support this model reported are discussed. Received5May 1976 7
ELECTRON SPIN RESONANCE INVESTIGATION OF THE PHASE TRANSITIONS INSTRUCTURAL Al urea 6(C104)3 AND Ga urea6(C104)3 LH.M. Mooy, Laboratory for Physical Chemistry, University of Amsterdam, Amsterdam, The Netherlands. Second order structural phase transitions in Al
Vol. 20, No.7
~.
Received 8 June 1976 THERMOCHEMISTRY OF AZIDE SALTS AND THE AZIDE ION USING DIRECT MINIMISATION CALCULATIONS FOR THE LATTICE ENERGY OF THE UNIVALENT AZIDE SALTS Harry Donald Brooke Jenkins and Kenneth Frank Pratt, School of Molecular Sciences, University ofWarwick, Coventry CV4 7AL, Warwickshire, U.K.
The opportunity to test a new equation for the computation of the lattice energy and at the same time examine a disparity in the literature data for the enthalpy of formation of the azide ion, ~H~(N~T)(z)was the motivation for this study. The results confirm our earlier calculation and show the new equation to be reliable. Thermodynamic data produced in the study take values: -
~Ht~(N3)(z) = 144 k~ z~H~~d(N~)(g) = 315 kJ moF’ —
or ~~~d(N3Xg) UPOT(NaN3) UPOT(KN 3) UPOT(RbN3) UPOT(CSN3) UPOT(T1N3)
= =
= =
= =
295 kJ mol_i 1 732 kJ moF —
659 kJ mol’ 637kJmoF’ 612 kJmoF’ 1 689 kJ moF
The lattice energies of azides whose enthalpies of formation are documented have been calculated as well as the enthalpy of formation of the azide radical. Received 28 April 1976
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
nitrogen centre previously reported, characterised by a 14N) = 7.5 G and A 4N) = hyperfine 11( 1(’ 5.0 G. Thistriplet centrewithA was accompanied by the common nitrogen centre in only one case. Other naturally occurring centres, apparently comprising two weakly coupled electrons in triplet states, were too poorly defmed to characterise fully. Received 19 May 1975 Revised 6August 1976 5
SELENIUM CRYSTALLIZATION INDUCED BY COROTRON CHARGING H.W. Pinsler and W.E. Brower, Xerox Corporation, Webster, NY 14580, U.S.A.
ur6(C104)3 and Ga ur6(C1O4)3 with T~= 300 K are studied by means of ESR on single crystals doped with the analogous Cr(III) compound. The transitions are antiferrodistortive and of the displacive type, the displacements resulting from the condensa.tion of aX 2 mode [k = (0 ~ ~)1of the dO4 ions. The ESR parameters have the same temperature dependence as the order parameters and can be described byD and E lØ~.The space group describing the structure changes from S~to S~,and the number of domains is multiplied by three. Above 300 K the crystals already consist of two domains, resulting from a ferrodistortive phase transition D~d S The actual transition temperature ofthe latter phase transition lies at some temperature above the decomposition temperature of the crystals. -~
Amorphous selenium films were exposed to corotron charging and simultaneous photo discharging. Corotron charging increased considerably the rate of crystal8 lization compared to photocrystaffization. This increase was manifested as a higher top surface nucleation rate m the corotron charged regions. An ion recombination mechanism is proposed to explain the enhanced crystallization due to corotron charging. • Received 4May 1976 • Revised 6 August 1976 6
PROPERTIES SUGGESTING H-TYPE CLUSTERS IN SOME METALLIC HYDRIDES D. Lupu and R.V. Bucur, Institute of Stable Isotopes, Cluj-Napoca, P.O. Box 243, Str. Donath 65-103, Romania.
The p—c—-T relationships for the hydrogen-rich phase of some metallic hydrides are calculated supposing the formation of H-type clusters in the metal lattice in equilibrium with the hydrogen gas. The experimental data for the hydride phase of LaNi5, Pd, Nb(HINb ~ 0.75) and U are consistent with this model. Other properties in literature which seem to support this model reported are discussed. Received5May 1976 7
ELECTRON SPIN RESONANCE INVESTIGATION OF THE PHASE TRANSITIONS INSTRUCTURAL Al urea 6(C104)3 AND Ga urea6(C104)3 LH.M. Mooy, Laboratory for Physical Chemistry, University of Amsterdam, Amsterdam, The Netherlands. Second order structural phase transitions in Al
Vol. 20, No.7
~.
Received 8 June 1976 THERMOCHEMISTRY OF AZIDE SALTS AND THE AZIDE ION USING DIRECT MINIMISATION CALCULATIONS FOR THE LATTICE ENERGY OF THE UNIVALENT AZIDE SALTS Harry Donald Brooke Jenkins and Kenneth Frank Pratt, School of Molecular Sciences, University ofWarwick, Coventry CV4 7AL, Warwickshire, U.K.
The opportunity to test a new equation for the computation of the lattice energy and at the same time examine a disparity in the literature data for the enthalpy of formation of the azide ion, ~H~(N~T)(z)was the motivation for this study. The results confirm our earlier calculation and show the new equation to be reliable. Thermodynamic data produced in the study take values: -
~Ht~(N3)(z) = 144 k~ z~H~~d(N~)(g) = 315 kJ moF’ —
or ~~~d(N3Xg) UPOT(NaN3) UPOT(KN 3) UPOT(RbN3) UPOT(CSN3) UPOT(T1N3)
= =
= =
= =
295 kJ mol_i 1 732 kJ moF —
659 kJ mol’ 637kJmoF’ 612 kJmoF’ 1 689 kJ moF
The lattice energies of azides whose enthalpies of formation are documented have been calculated as well as the enthalpy of formation of the azide radical. Received 28 April 1976