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Interatomic forces in the B.C.C. transition metals
ii
ABSTRACTS OF ARTICLES TO BE PUBLISHED IN THE J. PHYS. CHEM. SOLIDS Vol. 37, No. 8
an effect of the structural misalignments usually present in natural samples of graphite.
Received lOMareh 1980 Revised 18 August 1980 5.
STATIC AND DYNAMIC DISORDERED STATES IN VO2+-DOPED BaC12" 2H20 CRYSTALS M. Suhara and K. Iikawa, Department of Chemistry, Faculty of Science, Kanazawa University, Kanazawa 920, Japan
From the EPR investigation, two different crystalline states were found in the VO 2+ ion-doped BaCl2" 2H20 crystal. One is a dynamic disordered state, where the trapped VO 2+ ion exhibits hindered rotational motion in a wide temperature region. This state is transformed to a static disordered state even at ambient temperature. The orientation of the doped ion reveals random distribution in the lattice sites. Such polymorphism does not come from phase transition of the host crystal, but from the existence of the metastable state of the VO 2+ ion trapped in the lattice. The absence of the phase transition of pure BaC12" 2H20 was confirmed by the measurement of 137BaNQR and by differential thermal analysis.
Received 27 May 1980 Revised 26 September 1980 6.
HIGH PRESSURE PHASE TRANSITION IN PbSnTe T. Suski and J. Karpiriski, "UNIPRESS", High Pressure Research Center, Polish Academy of Sciences, Warszawa, Sokotowska 29, Poland; and K.L.I. Kobayashi, K.F. Komatsubara, Central Research Laboratory, Hitachi Ltd., Kokubunji, Tokyo 185, Japan
The high pressure structural phase transition in the alloy series Pbl_xSnxTe has been investigated using resistivity and Hall coefficient measurements. With increasing of tin content the critical pressure decreases linearly and the phase transition becomes less drastic. The anomalous behavior of the resistivity in the phase transition region is explained by band structure changes. It is suggested that the high pressure phase transition in Pbl-xSnxTe is a metallic-covalent transition.
Received 14March 1980 .
ON THE BEHAVIOR OF Nd a÷ IN LaCla D. Neogy and A. Chatterji, Solid State Research Laboratory, Department of Physics, Burdwan University, Burdwan 713 104, West Bengal, India
Various properties of Nd a+ : LaC13 which are influenced strongly by the crystalline electric field (CF) have been studied in the intermediate coupling scheme. A satisfactory correlation among the diverse observed properties has been achieved with the CF of Crosswhite et al. The hitherto uncertain lattice contribution to the electric field gradient (EFG) at the nuclear site has been established quite precisely. Some interesting features in the magnetic and thermal behavior of Nd 3÷ are also predicted.
Received 5 July 1980 8.
INTERATOMIC FORCES IN THE B.C.C. TRANSITION METALS C.C. Matthai, PA. Grout and N.H. March, Theoretical Chemistry Department 1 South Parks Road, Oxford
Using information obtained from X-ray scattering data, a model for the charge density in the transition metals is constructed. In this model the charge density is given by the sum of the charges situated at the ionic and bond centre sites. Within this framework, expressions for the second order elastic constants and the phonon frequencies in the cubic transition metals are obtained. These quantities have been calculated with and without the bond charge contributions for iron. The comparison with the experimental results shows that the introduction of bond charges, and hence angularity in the forcefields, in iron leads to distinctly better agreement with experiment. From a study of the elastic constants of the other b.c.c, transition metals some observations as to the nature of the angular force fields are made.
Received 2 July 1980 Revised 26 September 1980 9.
THE SOLUTION OF HYDROGEN IN TaV2 James F. Lynch, Brookhaven National Laboratory, Department of Energy and Environment, Upton, NY 11973, U.S.A.
TaV2 may be prepared as a random b.c.c, alloy or as a (C-15) Laves phase. The behavior of hydrogen dissolved in b.c.c. TaV2 is significantly different than that exhibited by hydrogen dissolved in (C-15)TaV2. The b.c.c. TaV2/H2 system is similar to pure vanadium/H2; in the region of hydrogen solid solution, the electronic contribution to the thermodynamics of solution is negligible and the system exhibits apparent H - H attractive interactions. A non-stoichiometric f.c.c, dihydride is formed at pH 2 = 10 atm, T = 273 K. (C-15)TaV2 does not form a hydride phase; hydrogen is continuously absorbed into solid solution to a maximum hydrogen content HIM 0.60. The solid solution of hydrogen in (C-15)TaV2 exhibits trends which are typical of intermetaUic/H2
ABSTRACTS OF ARTICLES TO BE PUBLISHED IN THE J. PHYS. CHEM. SOLIDS Vol. 37, No. 8
an effect of the structural misalignments usually present in natural samples of graphite.
Received lOMareh 1980 Revised 18 August 1980 5.
STATIC AND DYNAMIC DISORDERED STATES IN VO2+-DOPED BaC12" 2H20 CRYSTALS M. Suhara and K. Iikawa, Department of Chemistry, Faculty of Science, Kanazawa University, Kanazawa 920, Japan
From the EPR investigation, two different crystalline states were found in the VO 2+ ion-doped BaCl2" 2H20 crystal. One is a dynamic disordered state, where the trapped VO 2+ ion exhibits hindered rotational motion in a wide temperature region. This state is transformed to a static disordered state even at ambient temperature. The orientation of the doped ion reveals random distribution in the lattice sites. Such polymorphism does not come from phase transition of the host crystal, but from the existence of the metastable state of the VO 2+ ion trapped in the lattice. The absence of the phase transition of pure BaC12" 2H20 was confirmed by the measurement of 137BaNQR and by differential thermal analysis.
Received 27 May 1980 Revised 26 September 1980 6.
HIGH PRESSURE PHASE TRANSITION IN PbSnTe T. Suski and J. Karpiriski, "UNIPRESS", High Pressure Research Center, Polish Academy of Sciences, Warszawa, Sokotowska 29, Poland; and K.L.I. Kobayashi, K.F. Komatsubara, Central Research Laboratory, Hitachi Ltd., Kokubunji, Tokyo 185, Japan
The high pressure structural phase transition in the alloy series Pbl_xSnxTe has been investigated using resistivity and Hall coefficient measurements. With increasing of tin content the critical pressure decreases linearly and the phase transition becomes less drastic. The anomalous behavior of the resistivity in the phase transition region is explained by band structure changes. It is suggested that the high pressure phase transition in Pbl-xSnxTe is a metallic-covalent transition.
Received 14March 1980 .
ON THE BEHAVIOR OF Nd a÷ IN LaCla D. Neogy and A. Chatterji, Solid State Research Laboratory, Department of Physics, Burdwan University, Burdwan 713 104, West Bengal, India
Various properties of Nd a+ : LaC13 which are influenced strongly by the crystalline electric field (CF) have been studied in the intermediate coupling scheme. A satisfactory correlation among the diverse observed properties has been achieved with the CF of Crosswhite et al. The hitherto uncertain lattice contribution to the electric field gradient (EFG) at the nuclear site has been established quite precisely. Some interesting features in the magnetic and thermal behavior of Nd 3÷ are also predicted.
Received 5 July 1980 8.
INTERATOMIC FORCES IN THE B.C.C. TRANSITION METALS C.C. Matthai, PA. Grout and N.H. March, Theoretical Chemistry Department 1 South Parks Road, Oxford
Using information obtained from X-ray scattering data, a model for the charge density in the transition metals is constructed. In this model the charge density is given by the sum of the charges situated at the ionic and bond centre sites. Within this framework, expressions for the second order elastic constants and the phonon frequencies in the cubic transition metals are obtained. These quantities have been calculated with and without the bond charge contributions for iron. The comparison with the experimental results shows that the introduction of bond charges, and hence angularity in the forcefields, in iron leads to distinctly better agreement with experiment. From a study of the elastic constants of the other b.c.c, transition metals some observations as to the nature of the angular force fields are made.
Received 2 July 1980 Revised 26 September 1980 9.
THE SOLUTION OF HYDROGEN IN TaV2 James F. Lynch, Brookhaven National Laboratory, Department of Energy and Environment, Upton, NY 11973, U.S.A.
TaV2 may be prepared as a random b.c.c, alloy or as a (C-15) Laves phase. The behavior of hydrogen dissolved in b.c.c. TaV2 is significantly different than that exhibited by hydrogen dissolved in (C-15)TaV2. The b.c.c. TaV2/H2 system is similar to pure vanadium/H2; in the region of hydrogen solid solution, the electronic contribution to the thermodynamics of solution is negligible and the system exhibits apparent H - H attractive interactions. A non-stoichiometric f.c.c, dihydride is formed at pH 2 = 10 atm, T = 273 K. (C-15)TaV2 does not form a hydride phase; hydrogen is continuously absorbed into solid solution to a maximum hydrogen content HIM 0.60. The solid solution of hydrogen in (C-15)TaV2 exhibits trends which are typical of intermetaUic/H2