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Calculation of electrostatic fields in ionic crystals by a Bertaut method
vi
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
v2 to the ordering energy in the first coordination sphere Vi is discussed. In many respects the results are essentially different from those known earlier and are in agreement with experiment. This gives new opportunity to the classical ordering theory for a quantitative description of some binary systems. Received 3 June 1974
4.
CALCULATION OF ELECTROSTATIC FIELDS IN IONIC CRYSTALS BY A BERTAUT METHOD J.W. Weenk and H.A. Harwig, Inorganic Chemistry Department, State University Utrecht, Croesestraat 77A, Utrecht, The Netherlands.
A method to calculate the electrostatic field strength in ionic crystals is evaluated according to a model by Bertaut. Formulae for the self potential and the field strength at an ion site are derived. The practical use is demonstrated by calculations of field vectors in TiO 2 (rutile, anatase, brookite), idealized hexagonal perovskite, CdJ2, CdCI2, t3-Si02, PbCl2, PbBr2, PbFC1, PbFBr, Pb02, CdFeO3, KCuF3, BaNiO2, CsNiCI2, KFeS2, ZrO2, PbTiO3, AgCuS, Ag2S, CuF2, CuO, MoO3, Cr2O3, K2S208, MoO2, VF3 and Pb203. For 11 structures the results are compared with those obtained from potential calculations by the Ewald method, Received 8May 1974 Revised 30 October 1974
Vol. 16, No. 7
4 and Ag~’,Br0 substitutionalThe impurities Rb respectively. measurements were carried out at 78 K and 298 K. The defects diminish the integral intensity of the resonance signal and cause an increase of the line width and a shift of the line center. The magnitude of these effects depends on the temperature. Using the results of X-ray diffraction and Raman measurements made on the same samples, the observed perturbations of the chlorine-35 NQR signal can be interpreted satisfactorily by means of model of an elastically distorted lattice. Received 17 June 1974 Revised 20 December 1974
6.
X-RAY DIFFRACTION STUDIES OF IRRADIATED LITHIUM HYDRIDE: ORIENTED LITHIUM PRECIPITATES Gordon S. Smith, Lawrence Livermore Laboratory, University of California, Livermore, California 94550, U.S.A.
Single-crystal X-ray diffraction studies of gammairradiated LiH show the clear presence of metallic lithium precipitates. The lithium is in the normal b.c.c. form and is crystallographically oriented with respect to the matrix: {1lO}~II [111}UH and (1 OO>~11<11 °~LjH~ The absence of diffraction broadening is evidence that the Li particles are relatively large ~ 50 nm). X-ray diffraction measurements of the Li content of a heavily irradiated LiH crystal indicate that a substantial fraction of the “free” Li is present in the oriented precipitates. Received 26 November 1974
5.
INFLUENCE OF POINT DEFECTS ON THE NUCLEAR QUADRUPOLE RESONANCE 35C1 IN KCIO OF 3 AND NaCIO3 J. Pelzl, I-I. Vargas and D. Dautreppe, Department de Recherche Fondamentale, Centre d’Etudes Nucl~airesde Grenoble, BP 85 Centre de Tn, 38 041 Grenoble, Cedex, France, and H. Schulz, Fachbereich Physik, Freie Universität Berlin, Germany.
The nuclear quadrupole resonance of 35Cl was studies in 7-irradiated NaC1O 3 single crystals and in polycrystalline KC1O3 and NaClO3 doped with the
7.
CHARACTERISTICS OF THE H~Lj CENTER IN DETERMINED ELECTRON-IRRADIATED 4’ AS BY ESR NaF: Li TECHNIQUES William J. Plant, Naval Research Laboratory, Washington, D.C. 20375, U.S.A.
An ESR study shows that a center involving two fluorine interstitials is produced in NaF: LI4’ by electron irradiation near liquid nitrogen temperature. An angular dependence study of the ESR spectrum
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
v2 to the ordering energy in the first coordination sphere Vi is discussed. In many respects the results are essentially different from those known earlier and are in agreement with experiment. This gives new opportunity to the classical ordering theory for a quantitative description of some binary systems. Received 3 June 1974
4.
CALCULATION OF ELECTROSTATIC FIELDS IN IONIC CRYSTALS BY A BERTAUT METHOD J.W. Weenk and H.A. Harwig, Inorganic Chemistry Department, State University Utrecht, Croesestraat 77A, Utrecht, The Netherlands.
A method to calculate the electrostatic field strength in ionic crystals is evaluated according to a model by Bertaut. Formulae for the self potential and the field strength at an ion site are derived. The practical use is demonstrated by calculations of field vectors in TiO 2 (rutile, anatase, brookite), idealized hexagonal perovskite, CdJ2, CdCI2, t3-Si02, PbCl2, PbBr2, PbFC1, PbFBr, Pb02, CdFeO3, KCuF3, BaNiO2, CsNiCI2, KFeS2, ZrO2, PbTiO3, AgCuS, Ag2S, CuF2, CuO, MoO3, Cr2O3, K2S208, MoO2, VF3 and Pb203. For 11 structures the results are compared with those obtained from potential calculations by the Ewald method, Received 8May 1974 Revised 30 October 1974
Vol. 16, No. 7
4 and Ag~’,Br0 substitutionalThe impurities Rb respectively. measurements were carried out at 78 K and 298 K. The defects diminish the integral intensity of the resonance signal and cause an increase of the line width and a shift of the line center. The magnitude of these effects depends on the temperature. Using the results of X-ray diffraction and Raman measurements made on the same samples, the observed perturbations of the chlorine-35 NQR signal can be interpreted satisfactorily by means of model of an elastically distorted lattice. Received 17 June 1974 Revised 20 December 1974
6.
X-RAY DIFFRACTION STUDIES OF IRRADIATED LITHIUM HYDRIDE: ORIENTED LITHIUM PRECIPITATES Gordon S. Smith, Lawrence Livermore Laboratory, University of California, Livermore, California 94550, U.S.A.
Single-crystal X-ray diffraction studies of gammairradiated LiH show the clear presence of metallic lithium precipitates. The lithium is in the normal b.c.c. form and is crystallographically oriented with respect to the matrix: {1lO}~II [111}UH and (1 OO>~11<11 °~LjH~ The absence of diffraction broadening is evidence that the Li particles are relatively large ~ 50 nm). X-ray diffraction measurements of the Li content of a heavily irradiated LiH crystal indicate that a substantial fraction of the “free” Li is present in the oriented precipitates. Received 26 November 1974
5.
INFLUENCE OF POINT DEFECTS ON THE NUCLEAR QUADRUPOLE RESONANCE 35C1 IN KCIO OF 3 AND NaCIO3 J. Pelzl, I-I. Vargas and D. Dautreppe, Department de Recherche Fondamentale, Centre d’Etudes Nucl~airesde Grenoble, BP 85 Centre de Tn, 38 041 Grenoble, Cedex, France, and H. Schulz, Fachbereich Physik, Freie Universität Berlin, Germany.
The nuclear quadrupole resonance of 35Cl was studies in 7-irradiated NaC1O 3 single crystals and in polycrystalline KC1O3 and NaClO3 doped with the
7.
CHARACTERISTICS OF THE H~Lj CENTER IN DETERMINED ELECTRON-IRRADIATED 4’ AS BY ESR NaF: Li TECHNIQUES William J. Plant, Naval Research Laboratory, Washington, D.C. 20375, U.S.A.
An ESR study shows that a center involving two fluorine interstitials is produced in NaF: LI4’ by electron irradiation near liquid nitrogen temperature. An angular dependence study of the ESR spectrum