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Lutetium:High pressure polymorph and compression
Vol. 15, No.3
8.
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
STABILITY OF A15 TYPE PHASES L.D. Hartsough, Inorganic Materials Research Division, Lawrence Berkeley Laboratory and Department of Materials Science and Engineering, College of Engineering; University of California, Berkeley, California, U.S.A.
10.
LUTETIUM: HIGH PRESSURE POLYMORPH AND COMPRESSION Lin-gun Liu, Department of Geological Sciences, University of Rochester, Rochester, New York 14627, U.S.A.
Previous works dealing with the stability of the A15 phases are reviewed. Data for over 60 known A15 phases are used to develop criteria for stability which may be applied to hypothetical Al 5 phases. Occurrence of these phases is examined in terms of the valence bond concepts of the Engel—Brewer correlation and in its frequency with changes in electronic density of states. A15 is most favored when the “A” elements are V. Nb, or Cr, when radii of the constituent atoms differ by no more than 8 per cent, at compositions determined by electron concentration, and at relatively low temperatures. Composition and temperature of formation are predicted for several likely hypothetical A15 phases.
The effect of pressure on the lattice parameters of the h.c.p. phase of Lu has been studied up to 230 kbar at 23 ±3°Cby means of X.ray diffraction employing a diamond-anvil cell. The data fitted to the Birch equation yield an isothermal bulk modulus of 460 ±20 kbar with a pressure derivative of 2.8 ±0.5. The axial ratio (c/a) decreases nonlinearly with increasing pressure, the decrease being 2.4 per cent at 230 kbar. When the pressure exceeds 230 kbar, Lu transforms reversibly from the h.c.p. phase to the Sm-type structure. The transition occurs with increasing pressure in the range of 230 ±5 kbar. The lattice parameters of the Sm-type structure at about 231 kbar are a = 3.176 ±0.006A and c = 21.77 ± 0.04 A, and the volume change is —0.21 cm3/mol or —1.6 per cent of the volume of the h.c.p. phase.
Received 30 July 1973 Revised 19 March 1974
Received 9 October 1973 Revised 1 April 1974
9.
ON THE CHARGE DISTRIBUTION IN MANGANESE BORIDES STUDIED BY X-RAY PHOTOELECTRON AND EMISSION SPECTROSCOPY V.V. Nemoshkalenko, T.B. Sashkina, V.G. Aljeshin and A.I. Senkevich, Institute of Metal Physics, Kiev, USSR.
For the borides of the Mn—B system the values of binding energies of Mn 3p, 2P3/2’ 2p 112 and B ls core levels were measured on an electron spectrometer. Depending on boride composition the variation of inner level energies is very similar, showing a change of sign in the region of the monoboride phase. The same variation has been observed for some characteristics of X-ray emission spectra from these borides. An attempt is made to understand which of the chemical bonding factors are chiefly responsible for a regular concentration dependence of the X-ray and photoelectron spectra. Received 3 July 1973 Revised 3 April 1974
11.
vii
THERMAL IMPEDANCE ACROSS METALLIC AND SUPERCONDUCTING FOILS BELOW 1 K S.G. O’Hara and A.C. Anderson, Department of Physics and MaterialsofResearch Laboratory, University Illinois, Urbana, Illinois 61801, U.S.A. The thermal boundary resistance at the interface
between a metal and a dielectric has been investigated using thin foils to avoid the necessity of measuring temperature gradients. Measurements in the normal state are in good agreement with the acoustic mismatch concept of the boundary resistance when the effects of electron—phonon interaction in the metal are included. Since the electron—phonon interaction is reduced or absent in the superconducting state, a change in the boundary resistance is predicted by the acoustic mismatch model. Indeed the measurements in the superconducting state can be understood within the context of the model. However a quantitative interpretation is complicated by the presence of additional phonon scattering attributed to vibration dislocations. Received l9Janua,y 1974 Revised 5 April 1974
8.
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
STABILITY OF A15 TYPE PHASES L.D. Hartsough, Inorganic Materials Research Division, Lawrence Berkeley Laboratory and Department of Materials Science and Engineering, College of Engineering; University of California, Berkeley, California, U.S.A.
10.
LUTETIUM: HIGH PRESSURE POLYMORPH AND COMPRESSION Lin-gun Liu, Department of Geological Sciences, University of Rochester, Rochester, New York 14627, U.S.A.
Previous works dealing with the stability of the A15 phases are reviewed. Data for over 60 known A15 phases are used to develop criteria for stability which may be applied to hypothetical Al 5 phases. Occurrence of these phases is examined in terms of the valence bond concepts of the Engel—Brewer correlation and in its frequency with changes in electronic density of states. A15 is most favored when the “A” elements are V. Nb, or Cr, when radii of the constituent atoms differ by no more than 8 per cent, at compositions determined by electron concentration, and at relatively low temperatures. Composition and temperature of formation are predicted for several likely hypothetical A15 phases.
The effect of pressure on the lattice parameters of the h.c.p. phase of Lu has been studied up to 230 kbar at 23 ±3°Cby means of X.ray diffraction employing a diamond-anvil cell. The data fitted to the Birch equation yield an isothermal bulk modulus of 460 ±20 kbar with a pressure derivative of 2.8 ±0.5. The axial ratio (c/a) decreases nonlinearly with increasing pressure, the decrease being 2.4 per cent at 230 kbar. When the pressure exceeds 230 kbar, Lu transforms reversibly from the h.c.p. phase to the Sm-type structure. The transition occurs with increasing pressure in the range of 230 ±5 kbar. The lattice parameters of the Sm-type structure at about 231 kbar are a = 3.176 ±0.006A and c = 21.77 ± 0.04 A, and the volume change is —0.21 cm3/mol or —1.6 per cent of the volume of the h.c.p. phase.
Received 30 July 1973 Revised 19 March 1974
Received 9 October 1973 Revised 1 April 1974
9.
ON THE CHARGE DISTRIBUTION IN MANGANESE BORIDES STUDIED BY X-RAY PHOTOELECTRON AND EMISSION SPECTROSCOPY V.V. Nemoshkalenko, T.B. Sashkina, V.G. Aljeshin and A.I. Senkevich, Institute of Metal Physics, Kiev, USSR.
For the borides of the Mn—B system the values of binding energies of Mn 3p, 2P3/2’ 2p 112 and B ls core levels were measured on an electron spectrometer. Depending on boride composition the variation of inner level energies is very similar, showing a change of sign in the region of the monoboride phase. The same variation has been observed for some characteristics of X-ray emission spectra from these borides. An attempt is made to understand which of the chemical bonding factors are chiefly responsible for a regular concentration dependence of the X-ray and photoelectron spectra. Received 3 July 1973 Revised 3 April 1974
11.
vii
THERMAL IMPEDANCE ACROSS METALLIC AND SUPERCONDUCTING FOILS BELOW 1 K S.G. O’Hara and A.C. Anderson, Department of Physics and MaterialsofResearch Laboratory, University Illinois, Urbana, Illinois 61801, U.S.A. The thermal boundary resistance at the interface
between a metal and a dielectric has been investigated using thin foils to avoid the necessity of measuring temperature gradients. Measurements in the normal state are in good agreement with the acoustic mismatch concept of the boundary resistance when the effects of electron—phonon interaction in the metal are included. Since the electron—phonon interaction is reduced or absent in the superconducting state, a change in the boundary resistance is predicted by the acoustic mismatch model. Indeed the measurements in the superconducting state can be understood within the context of the model. However a quantitative interpretation is complicated by the presence of additional phonon scattering attributed to vibration dislocations. Received l9Janua,y 1974 Revised 5 April 1974