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Temperature dependence of the infrared optical properties of LiF
iv
3.
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
A GALVANOMAGNETIC INVESTIGATION OF TiB2, NbB2 AND ZrB2 William Gordon Jr. and Stephen B. Soffer, Polytechnic Institute of Brooklyn, Brooklyn, New York 11201, U.S.A.
Low temperature measurements were made of the transverse magnetoresistivity and Hall coefficient of single crystals of nominal compositions TiB2, NbBZ and ZrB2 as a function of magnetic field strength. The data are compared to predictions of the two-band spherical Fermi surface model. For TiB2 and NbB2 predictions of the model can be made to conform reasonably well to the experimental results. Results for ZrB2 do not fit the model as well, perhaps, because of a larger deviation from stoichiometry. In spite of low resistance ratios (~ 100) the crystals exhibit behavior characteristic of intermediate field strengths (wr >0.1) at liquid helium temperatures. This implies that light mass carriers predominate. Received 21 January 1974
S. Isotani, W. Sano and J.A. Ochi, Instituto de Fisica da Universidade de São Paulo, C.P. 20516, São Paulo, Brasil. Far i.r. spectra of Ni(NO3)26NH3 were recorded above and below the order—disorder phase transition at T~= 243 K. The results are compared to the spectra of the isomorphous crystal NiC126NH3, which has no transition in the same temperature range. The antisymmetric stretching vibration of the ammonias shows a broken degeneracy below T~for Ni(NO3)2 6NH3. No broken degeneracy was observed in the nickel—nitrogen vibration of the INi(NH3)6I~ clusters. The discussion of our results lends support to the assumption that the phase transition is due to the collective freezing of the degrees of rotation of the~ammonias. Received 5 Feburary 1974 Revised 24 June 1974
6. 4.
TEMPERATURE DEPENDENCE OF THE INFRARED OPTICAL PROPERTIES OF LiF A.H. Kachare, G. Andermann and M.P. Soriaga, Department of Chemistry and Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii 96822, U.S.A.
Essentially distortion-free imaginary dielectric index spectra have been obtained for LiF from Kramers—Kronig (KK) dispersion analysis of infrared reflectance data at 300, 80 and 20°K.The frequency dependence of the damping function as well as the temperature dependence of the various dispersion parameters of the first transverse optic mode have been illustrated. The effective damping constant and the resonance frequency v0, are found to be in satisfactory agreement with the theoretical calculations.
Vol. 15, No. 8
COULOMBIC POTENTIAL LATTICE SUMS A. Redlack and J. Grindlay, Physics Department, University of Waterloo, Waterloo, Ontario, Canada.
An expression is derived for the electrostatic potential in an ellipsoidal crystalline system of point charges. The potential consists of two components: one, the intrinsic potential, is a periodic function of position and is independent of the shape and size of the ellipsoid; the other, the extrinsic potential, is a quadratic function of position and is a function of the shape and size of the ellipsoid. Ifthe charge repetition unit is electrically neutral, the size dependence vanishes and the quadratic dependence reduces to a linear dependence.
~,
Received 7 March 1974
5.
PHASE TRANSITION IN METAL HEXAMMINE COMPLEXES I. THE -
INFRARED SPECTRA OF Ni(NO3)26NH3
An infinite lattice electrostatic potential is defined and existence conditions obtained. It is shown that Madelung’s and Evjen’s potentials are special cases of the infinite lattice electrostatic potential whereas Ewald’s potential is equal to the intrinsic potential. The relationship between these three potentials is discussed. Received 11 Febn~ary1974
3.
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
A GALVANOMAGNETIC INVESTIGATION OF TiB2, NbB2 AND ZrB2 William Gordon Jr. and Stephen B. Soffer, Polytechnic Institute of Brooklyn, Brooklyn, New York 11201, U.S.A.
Low temperature measurements were made of the transverse magnetoresistivity and Hall coefficient of single crystals of nominal compositions TiB2, NbBZ and ZrB2 as a function of magnetic field strength. The data are compared to predictions of the two-band spherical Fermi surface model. For TiB2 and NbB2 predictions of the model can be made to conform reasonably well to the experimental results. Results for ZrB2 do not fit the model as well, perhaps, because of a larger deviation from stoichiometry. In spite of low resistance ratios (~ 100) the crystals exhibit behavior characteristic of intermediate field strengths (wr >0.1) at liquid helium temperatures. This implies that light mass carriers predominate. Received 21 January 1974
S. Isotani, W. Sano and J.A. Ochi, Instituto de Fisica da Universidade de São Paulo, C.P. 20516, São Paulo, Brasil. Far i.r. spectra of Ni(NO3)26NH3 were recorded above and below the order—disorder phase transition at T~= 243 K. The results are compared to the spectra of the isomorphous crystal NiC126NH3, which has no transition in the same temperature range. The antisymmetric stretching vibration of the ammonias shows a broken degeneracy below T~for Ni(NO3)2 6NH3. No broken degeneracy was observed in the nickel—nitrogen vibration of the INi(NH3)6I~ clusters. The discussion of our results lends support to the assumption that the phase transition is due to the collective freezing of the degrees of rotation of the~ammonias. Received 5 Feburary 1974 Revised 24 June 1974
6. 4.
TEMPERATURE DEPENDENCE OF THE INFRARED OPTICAL PROPERTIES OF LiF A.H. Kachare, G. Andermann and M.P. Soriaga, Department of Chemistry and Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii 96822, U.S.A.
Essentially distortion-free imaginary dielectric index spectra have been obtained for LiF from Kramers—Kronig (KK) dispersion analysis of infrared reflectance data at 300, 80 and 20°K.The frequency dependence of the damping function as well as the temperature dependence of the various dispersion parameters of the first transverse optic mode have been illustrated. The effective damping constant and the resonance frequency v0, are found to be in satisfactory agreement with the theoretical calculations.
Vol. 15, No. 8
COULOMBIC POTENTIAL LATTICE SUMS A. Redlack and J. Grindlay, Physics Department, University of Waterloo, Waterloo, Ontario, Canada.
An expression is derived for the electrostatic potential in an ellipsoidal crystalline system of point charges. The potential consists of two components: one, the intrinsic potential, is a periodic function of position and is independent of the shape and size of the ellipsoid; the other, the extrinsic potential, is a quadratic function of position and is a function of the shape and size of the ellipsoid. Ifthe charge repetition unit is electrically neutral, the size dependence vanishes and the quadratic dependence reduces to a linear dependence.
~,
Received 7 March 1974
5.
PHASE TRANSITION IN METAL HEXAMMINE COMPLEXES I. THE -
INFRARED SPECTRA OF Ni(NO3)26NH3
An infinite lattice electrostatic potential is defined and existence conditions obtained. It is shown that Madelung’s and Evjen’s potentials are special cases of the infinite lattice electrostatic potential whereas Ewald’s potential is equal to the intrinsic potential. The relationship between these three potentials is discussed. Received 11 Febn~ary1974