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An error in the calculation of the rotational barrier in molecular crystals
Vol. 25, No.8 9.
ABSTRACTS OF ARTICLES TO APPEAR IN J. PHYS. CHEM. SOLIDS
ESR STUDIES OF EUROPIUM IONS IN ALKALI CHLORIDES M4D BROMIDES
tivity. The extra lattice thermal resistivity due to the presence of the ortho hydrogen and para deuterium is
Minoru Sumita, Katsuyasu Kawano and Ryohei Nakata, University of Electro-Communications, Chofusi, Tokyo, Japan.
alSO calculated. Received 8 June 1976 Revised 28 October 1977
vii
ESR studies of europium ions in alkali chlorides and bromides were performed at room and liquid nitrogen 12. AN ERROR IN THE CALCULATION OF THE temperatures. There were first reported spin Hamiltonian ROTATIONAL BARRIER IN MOLECULAR CRYSTALS parameters for NaBr : Eu2~and RbBr: Eu2~crystals and also for coagulated europium ions in NaCl, KC1, KBr and William R. Busing, Chemistry Division, Oak RbBr crystals. The dependence of b° 2 and b~on the Ridge National Laboratory, P.O. Box X, Oak lattice constant,2~6was a, of host crystalswhile was discussed; a single Ridge, TN 37830, U.S.A. obtained, relations for b~ relation b2° x separately a were treated for Na, K and Rb halide series, In calculating the potential barrier to molecular respectively. From the relative values of b~and b~, rotation in crystals several authors have reported results displacements of the nearest neighbor anions surrounding which are too small because a factor of one half was the Eu2~.vacancypair were estimated to be 0.083a for included by mistake. NaCl and NaBr, 0.081a for KC1, 0.080a for KBr, 0.074a Received 14 November 1977 for RbC1 and 0.078a for RbBr. Received 29 August 1977 Revised 28 October 1977 10.
13.
PHOTOLUMINESCENCE OF SrS : Cu PHOSPHORS B.B. Laud, Department of Physics, University of Poona, Poona 411 007, India; and V.W. Kulkarni, Milind College of Science, Aurangabad-43 1002, India.
THE EFFECT OF UNCERTAINTY IN THE EIGENDATA OF THE PURE HOST LATTICE ON GREENS-FUNCTION CALCULATIONS J.W. de Geus and O.L.J. Gijzeman, Laboratory for Physical Chemistry, University of Amsterdam, Nieuwe Prinsengracht 126, Amsterdam, The Netherlands.
The effect of the uncertainty in the eigendata of KI on gapmode calculations using the Greens-function Results of the investigation on the spectral character- technique has been examined. Certain eigenfrequencies istics of PL of SrS Cu phosphors are presented. Probable calculated with the Shell-model could be compared with emitters for the three observed bands, viz. 4710 A, expenmental singularities in the induced acoustic spec5200 A and 5480 A, have been suggested. trum of KI containing impurities. Changing the theorReceived 9 September 1977 Revised 28 October 1977 11.
HEAT TRANSFER IN SOLID HD AT LOW TEMPERATURES K.S. Dubey, Department of Physics, College of Science, University of Basrah, Basrah, Iraq.
The lattice thermal conductivity of solid HD has been calculated in the temperature range 0.2—4 K. The important scatterers of phonons are found to be boundary walls of the crystal, isotopic impurities, phonons and molecules of ortho hydrogen and para deuterium. The presence of molecules of ortho hydrogen and para deuterium in solid HD which act as rotational impurities, are responsible for one and two phonon scattering processes in the system. The entirethermal study isconductivity based on the Callaway model of the lattice of an insulator. Excellent agreement is found between calculated and experimental values of phonon conduc-
etical eigenfrequencies to the experimental values for insertion in the isotopic substitution model, which was used as a testcase for Greens-function calculations, result’~din an appreciable shift (— 0.3 cmt) in a gapmode frequency. Received 11 October 1977 14.
GROUND STATE IN FeS A. Leclerc and M.G. Townsend, Department of Energy, Mines and Resources, Ottawa, Ontario, Canada.
From a Mössbauer study of oriented single crystals of Fe 0 9%S and Fe0 93S at temperatures above the Néel transition (‘ 598 K), we have determined the sign of the quadruple splitting thereby confirming that the 5E. ground state is Received 23 August 1977 Revised 18 November 1977
ABSTRACTS OF ARTICLES TO APPEAR IN J. PHYS. CHEM. SOLIDS
ESR STUDIES OF EUROPIUM IONS IN ALKALI CHLORIDES M4D BROMIDES
tivity. The extra lattice thermal resistivity due to the presence of the ortho hydrogen and para deuterium is
Minoru Sumita, Katsuyasu Kawano and Ryohei Nakata, University of Electro-Communications, Chofusi, Tokyo, Japan.
alSO calculated. Received 8 June 1976 Revised 28 October 1977
vii
ESR studies of europium ions in alkali chlorides and bromides were performed at room and liquid nitrogen 12. AN ERROR IN THE CALCULATION OF THE temperatures. There were first reported spin Hamiltonian ROTATIONAL BARRIER IN MOLECULAR CRYSTALS parameters for NaBr : Eu2~and RbBr: Eu2~crystals and also for coagulated europium ions in NaCl, KC1, KBr and William R. Busing, Chemistry Division, Oak RbBr crystals. The dependence of b° 2 and b~on the Ridge National Laboratory, P.O. Box X, Oak lattice constant,2~6was a, of host crystalswhile was discussed; a single Ridge, TN 37830, U.S.A. obtained, relations for b~ relation b2° x separately a were treated for Na, K and Rb halide series, In calculating the potential barrier to molecular respectively. From the relative values of b~and b~, rotation in crystals several authors have reported results displacements of the nearest neighbor anions surrounding which are too small because a factor of one half was the Eu2~.vacancypair were estimated to be 0.083a for included by mistake. NaCl and NaBr, 0.081a for KC1, 0.080a for KBr, 0.074a Received 14 November 1977 for RbC1 and 0.078a for RbBr. Received 29 August 1977 Revised 28 October 1977 10.
13.
PHOTOLUMINESCENCE OF SrS : Cu PHOSPHORS B.B. Laud, Department of Physics, University of Poona, Poona 411 007, India; and V.W. Kulkarni, Milind College of Science, Aurangabad-43 1002, India.
THE EFFECT OF UNCERTAINTY IN THE EIGENDATA OF THE PURE HOST LATTICE ON GREENS-FUNCTION CALCULATIONS J.W. de Geus and O.L.J. Gijzeman, Laboratory for Physical Chemistry, University of Amsterdam, Nieuwe Prinsengracht 126, Amsterdam, The Netherlands.
The effect of the uncertainty in the eigendata of KI on gapmode calculations using the Greens-function Results of the investigation on the spectral character- technique has been examined. Certain eigenfrequencies istics of PL of SrS Cu phosphors are presented. Probable calculated with the Shell-model could be compared with emitters for the three observed bands, viz. 4710 A, expenmental singularities in the induced acoustic spec5200 A and 5480 A, have been suggested. trum of KI containing impurities. Changing the theorReceived 9 September 1977 Revised 28 October 1977 11.
HEAT TRANSFER IN SOLID HD AT LOW TEMPERATURES K.S. Dubey, Department of Physics, College of Science, University of Basrah, Basrah, Iraq.
The lattice thermal conductivity of solid HD has been calculated in the temperature range 0.2—4 K. The important scatterers of phonons are found to be boundary walls of the crystal, isotopic impurities, phonons and molecules of ortho hydrogen and para deuterium. The presence of molecules of ortho hydrogen and para deuterium in solid HD which act as rotational impurities, are responsible for one and two phonon scattering processes in the system. The entirethermal study isconductivity based on the Callaway model of the lattice of an insulator. Excellent agreement is found between calculated and experimental values of phonon conduc-
etical eigenfrequencies to the experimental values for insertion in the isotopic substitution model, which was used as a testcase for Greens-function calculations, result’~din an appreciable shift (— 0.3 cmt) in a gapmode frequency. Received 11 October 1977 14.
GROUND STATE IN FeS A. Leclerc and M.G. Townsend, Department of Energy, Mines and Resources, Ottawa, Ontario, Canada.
From a Mössbauer study of oriented single crystals of Fe 0 9%S and Fe0 93S at temperatures above the Néel transition (‘ 598 K), we have determined the sign of the quadruple splitting thereby confirming that the 5E. ground state is Received 23 August 1977 Revised 18 November 1977