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X-ray study of inner level shifts and band structure of TiC and related compounds
Vol.7, No.5
ABSTRACTS OF PAPERS TO APPEAR IN
Physics, University of California, Los Angeles, California 90024)
J.
PHYS. CHEM. SOLIDS
v
susceptibility measurements and Ned point. (Received 1 November 1968)
A detailed comparison of shock wave and static compression data for alkali metals reveals serious inconsistencies above 40 kbar. The reduction of shock wave results is reviewed, and the Bridgman high-pressure data on the alkali metals are described. It is shown that the most likely cause of this disagreement is inaccuracy in the static high-pressure data.
16.
(Received 26 August 1968)
14.
SECOND QUANTIZED FORMALISM FOR NON-ORTHOGONAL STATES D.J. Newman (Department of Physics, Queen Mary College, Mile End Road, London, E.1)
A simple method of manipulating annihilation and creation operators for non-orthogonal states is developed. This is applied in the context of crystal field theory to derive exact many electron matrix elements which are explicitly independent of.the choice of basis set and linked cluster in form. These are related to effective operators acting on fre’~-ionopen-shell states. (Received 2 December 1968)
15.
EXCHANGE CONSTANTS IN ORTHOFERRITES YFeO3 AND LuFeO3 G. Gorodetsky (Department of Electronics, The Meizmann Institute of Science, Rehovot, Israel)
The exchange interaction with nearest neighbors J1, next nearest neighbors J2, and the spectroscopic splitting factor g were determined for two orthoferrites YFeO3 and LuFeO3. A high temperature analysis of the paramagnetic susceptibility yielded the following results: For YFeO3, J1/k = —27’2 ±1°K,J2/k = —1’2 ±.2°K, g = 2.05 ±1; and for LuFeO3, J, / k = —24’2 ±1°K, J2/k = —1 ±.1°K,g = 2.00 ~ .05. Compatible values of ~1 were found from the low temperature
CHARGE TRANSFER IN TRANSITION METAL CARBIDES AND RELATED COMPOUNDS STUDIED BY ESCA Lam Ramqvist (The Axel Johnson Institute for Industrial Research, Nynäshamn, Sweden) Kjell Hamrin, Gunifla Johansson, Andems Fahiman and Carl Nordling (Institute of Physics, Uppsala University, Uppsala, Sweden)
Electron spectroscopic measurements of binding energy shifts of Cis electrons in Group 4b, 5b and 6b carbides and of core electrons in Ti and V compounds are presented. The results are discussed and compared with X-ray spectroscopic investigations and energy band calculations. It is shown that electrons are transferred from the metal to the carbon atoms when a carbide of this type is formed. (Received 3 December 1968)
17.
X-RAY STUDY OF INNER LEVEL SHIFTS AND BAND STRUCTURE OF TiC AND RELATED COMPOUNDS Lam Ramqvist (The Axel Johnson Institute for Industrial Research, Nyn~shamn,Sweden) Börje Ekstig, Elisabeth Källne and Erik Noreland (Institute of Physics, Uppsala University, Uppsala, Sweden) Roif Manne (Quantum Chemistry Group, Uppsala University, Uppsala, Sweden)
New measurements are presented of TiK absorption and emission spectra from TiC, TiN, TiO, TIB2, and Ti. It is shown that in all investigated compounds the number of Ti3d electrons is lower than in the pure metal. For the three cubic compounds the order of increasing ionicity is TiO, TiN, TiC. The results are discussed in conjunction with other X-ray and electron spectroscopical investigations and are shown to be in agreement with recent energy
vi
ABSTRACTS OF PAPERS TO APPEAR IN
band calculations using the self-consistent Augmented Plane Wave method.
COMPRESSIBILITY OF MOLECULAR ORGANIC COMPOUNDS T.C. Ehadra and G.C. Kennedy (Institute of Geophysics and Planetary Physics, University of California, Los Angeles)
The compressibility of a number of aromatic crystalline hydrocarbons, napthalene, anthracene, biphenyl, p-terphenyl, and substituted benzenes, p-dichlorobenzene and benzophenone have been measured to pressures of 35 kbars. Our new determinations of compressibility agree remarkably well with recent determinations to 12 kbars by Kabalkina. In general our results show compressions of from 10 to 25 per cent less than those reported by Bridgman. (Received 22 May 1968)
19.
THE JAHN—TELLER INSTABILITY WITH ACCIDENTAL DEGENERACY A.M. Stoneham and M. Lannoo (Coordinated Science Laboratory, University of Illinois, Urbana, Illinois 61801)
With accidental degeneracy it is possible to get mixed distortions which involve both trigonal and tetragonal distortions. These have probably been observed for the negative vacancy in silicon, and possibly for the neutral vacancy in diamond. The theory is applied to both these
Vol.7, No.5
(Received 11 October 1968) (Revised 6 January 1969)
20.
IMPURITY HALIDE DIFFUSION IN SILVER CHLORIDE AND SILVER BROMIDE A.P. Batra and L. Slifkin (Department of Physics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina)
Using the standard microtome-sectioning technique, the diffusion of bromide and iodide tracers in silver chloride and of chloride and iodide tracers in silver bromide has been studied. In silver chloride both bromide and iodide ions diffuse with the same activation energy as that of the chloride ion. In silver bromide the Arrhenius plots are curved: whereas the iodide ion has the same temperature-dependent activation energy as does bromide, the chloride ion appears to have a rather higher value at high temperatures, with all three energies approaching the same value at low temperatures. These results are discussed in terms of vacancy mechanisms. (Received 9 December 1968)
21. The Jahn—Teller theorem predicts that orbitally degenerate complexes in solids can lower their energy by a distortion which lowers their symmetry. Exact degeneracy is not necessary for this instability; usually it suffices if the actual separation of the energy levels involved is less than the energy reduction which would result if they were exactly degenerate. We discuss various cases of accidental degeneracy in cubic and tetrahedral systems.
PHYS. CHEM. SOLIDS
cases, and it is compared with the earlier qualitative arguments of Watkins.
(Received 30 September 1968) (Revised 3 December 1968)
18.
J.
ANODIC GROWTH, DIELECTRIC BREAKDOWN, AND CARRIER TRANSPORT IN AMORPHOUS Si02 FILMS C.R. Fritzsche (Institut für Elektrowerkstoffe, Freiburg, Germany)
Dielectric breakdown has been studied in anodically grown Si02 and compared with the growth conditions. It is found that avalanche multiplication of electrons and ionic conductivity are closely related. This supports the impact ionization theory of anodization recently published. An improved theory is given which supplies equations for efficiency of anodization, growth at constant current, and current decay at constant voltage in excellent agreement with experimental results. The effective mass ratio of electrons to ions, the mean free time of the
ABSTRACTS OF PAPERS TO APPEAR IN
Physics, University of California, Los Angeles, California 90024)
J.
PHYS. CHEM. SOLIDS
v
susceptibility measurements and Ned point. (Received 1 November 1968)
A detailed comparison of shock wave and static compression data for alkali metals reveals serious inconsistencies above 40 kbar. The reduction of shock wave results is reviewed, and the Bridgman high-pressure data on the alkali metals are described. It is shown that the most likely cause of this disagreement is inaccuracy in the static high-pressure data.
16.
(Received 26 August 1968)
14.
SECOND QUANTIZED FORMALISM FOR NON-ORTHOGONAL STATES D.J. Newman (Department of Physics, Queen Mary College, Mile End Road, London, E.1)
A simple method of manipulating annihilation and creation operators for non-orthogonal states is developed. This is applied in the context of crystal field theory to derive exact many electron matrix elements which are explicitly independent of.the choice of basis set and linked cluster in form. These are related to effective operators acting on fre’~-ionopen-shell states. (Received 2 December 1968)
15.
EXCHANGE CONSTANTS IN ORTHOFERRITES YFeO3 AND LuFeO3 G. Gorodetsky (Department of Electronics, The Meizmann Institute of Science, Rehovot, Israel)
The exchange interaction with nearest neighbors J1, next nearest neighbors J2, and the spectroscopic splitting factor g were determined for two orthoferrites YFeO3 and LuFeO3. A high temperature analysis of the paramagnetic susceptibility yielded the following results: For YFeO3, J1/k = —27’2 ±1°K,J2/k = —1’2 ±.2°K, g = 2.05 ±1; and for LuFeO3, J, / k = —24’2 ±1°K, J2/k = —1 ±.1°K,g = 2.00 ~ .05. Compatible values of ~1 were found from the low temperature
CHARGE TRANSFER IN TRANSITION METAL CARBIDES AND RELATED COMPOUNDS STUDIED BY ESCA Lam Ramqvist (The Axel Johnson Institute for Industrial Research, Nynäshamn, Sweden) Kjell Hamrin, Gunifla Johansson, Andems Fahiman and Carl Nordling (Institute of Physics, Uppsala University, Uppsala, Sweden)
Electron spectroscopic measurements of binding energy shifts of Cis electrons in Group 4b, 5b and 6b carbides and of core electrons in Ti and V compounds are presented. The results are discussed and compared with X-ray spectroscopic investigations and energy band calculations. It is shown that electrons are transferred from the metal to the carbon atoms when a carbide of this type is formed. (Received 3 December 1968)
17.
X-RAY STUDY OF INNER LEVEL SHIFTS AND BAND STRUCTURE OF TiC AND RELATED COMPOUNDS Lam Ramqvist (The Axel Johnson Institute for Industrial Research, Nyn~shamn,Sweden) Börje Ekstig, Elisabeth Källne and Erik Noreland (Institute of Physics, Uppsala University, Uppsala, Sweden) Roif Manne (Quantum Chemistry Group, Uppsala University, Uppsala, Sweden)
New measurements are presented of TiK absorption and emission spectra from TiC, TiN, TiO, TIB2, and Ti. It is shown that in all investigated compounds the number of Ti3d electrons is lower than in the pure metal. For the three cubic compounds the order of increasing ionicity is TiO, TiN, TiC. The results are discussed in conjunction with other X-ray and electron spectroscopical investigations and are shown to be in agreement with recent energy
vi
ABSTRACTS OF PAPERS TO APPEAR IN
band calculations using the self-consistent Augmented Plane Wave method.
COMPRESSIBILITY OF MOLECULAR ORGANIC COMPOUNDS T.C. Ehadra and G.C. Kennedy (Institute of Geophysics and Planetary Physics, University of California, Los Angeles)
The compressibility of a number of aromatic crystalline hydrocarbons, napthalene, anthracene, biphenyl, p-terphenyl, and substituted benzenes, p-dichlorobenzene and benzophenone have been measured to pressures of 35 kbars. Our new determinations of compressibility agree remarkably well with recent determinations to 12 kbars by Kabalkina. In general our results show compressions of from 10 to 25 per cent less than those reported by Bridgman. (Received 22 May 1968)
19.
THE JAHN—TELLER INSTABILITY WITH ACCIDENTAL DEGENERACY A.M. Stoneham and M. Lannoo (Coordinated Science Laboratory, University of Illinois, Urbana, Illinois 61801)
With accidental degeneracy it is possible to get mixed distortions which involve both trigonal and tetragonal distortions. These have probably been observed for the negative vacancy in silicon, and possibly for the neutral vacancy in diamond. The theory is applied to both these
Vol.7, No.5
(Received 11 October 1968) (Revised 6 January 1969)
20.
IMPURITY HALIDE DIFFUSION IN SILVER CHLORIDE AND SILVER BROMIDE A.P. Batra and L. Slifkin (Department of Physics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina)
Using the standard microtome-sectioning technique, the diffusion of bromide and iodide tracers in silver chloride and of chloride and iodide tracers in silver bromide has been studied. In silver chloride both bromide and iodide ions diffuse with the same activation energy as that of the chloride ion. In silver bromide the Arrhenius plots are curved: whereas the iodide ion has the same temperature-dependent activation energy as does bromide, the chloride ion appears to have a rather higher value at high temperatures, with all three energies approaching the same value at low temperatures. These results are discussed in terms of vacancy mechanisms. (Received 9 December 1968)
21. The Jahn—Teller theorem predicts that orbitally degenerate complexes in solids can lower their energy by a distortion which lowers their symmetry. Exact degeneracy is not necessary for this instability; usually it suffices if the actual separation of the energy levels involved is less than the energy reduction which would result if they were exactly degenerate. We discuss various cases of accidental degeneracy in cubic and tetrahedral systems.
PHYS. CHEM. SOLIDS
cases, and it is compared with the earlier qualitative arguments of Watkins.
(Received 30 September 1968) (Revised 3 December 1968)
18.
J.
ANODIC GROWTH, DIELECTRIC BREAKDOWN, AND CARRIER TRANSPORT IN AMORPHOUS Si02 FILMS C.R. Fritzsche (Institut für Elektrowerkstoffe, Freiburg, Germany)
Dielectric breakdown has been studied in anodically grown Si02 and compared with the growth conditions. It is found that avalanche multiplication of electrons and ionic conductivity are closely related. This supports the impact ionization theory of anodization recently published. An improved theory is given which supplies equations for efficiency of anodization, growth at constant current, and current decay at constant voltage in excellent agreement with experimental results. The effective mass ratio of electrons to ions, the mean free time of the