The Physics of Actinide Compounds

218 Pages·1983·9.11 MB·English

by  Paul Erdös

The Physics of
Actinide Compounds
PHYSICS OF SOLIDS AND LIQUIDS
Editorial Board: Josef T. Devreese • University of Antwerp, Belgium
Roger P. Evrard • University of Liege, Belgium
Stig Lundqvist • Chalmers University of Technology, Sweden
Gerald D. Mahan • Indiana University, Bloomington, Indiana
Norman H. March • University of Oxford, England
SUPERIONIC CONDUCTORS
Edited by Gerald D. Mahan and Walter L. Roth
HIGHLY CONDUCTING ONE-DIMENSIONAL SOLIDS
Edited by Jozef T. Devreese, Roger P. Evrard, and Victor E. van Doren
ELECTRON SPECTROSCOPY OF CRYSTALS
V. V. Nemoshkalenko and V. G. Aleshin
MANY- PARTICLE PHYSICS
Gerald D. Mahan
THE PHYSICS OF ACTINIDE COMPOUNDS
Paul Erdos and John M. Robinson
THEORY OF THE INHOMOGENEOUS ELECTRON GAS
Edited by S. Lundqvist and N. H. March
A Continuation Order Plan is available for this series. A continuation order wiII
bring delivery of each new volume immediately upon publication. Volumes are
biIIed only upon actual shipment. For further information please contact the
publisher.
The Physics of
Actinide Compounds
Paul ErdOs
University of Lausanne
Lausanne, Switzerland
and
John M. Robinson
Indiana University-Purdue University at Fort Wayne
Fort Wayne, Indiana
PLENUM PRESS • NEW YORK AND LONDON
Library of Congress Cataloging in Publication Data
Erdos, Paul, date -
The physics of actinide compounds.
(Physics of solids and liquids)
Bibliography: p.
Includes index.
1. Actinide elements. I. Robinson, John M., date - . II. Title. III. Series.
QD172.A3E73 1983 546'.4 83c2331
ISBN-13: 978-1-4613-3583-2 e-ISBN-13: 978-1-4613-3581-8
DOl: 10.1007/978-1-4613-3581-8
© 1983 Plenum Press, New York
Sotfcover reprint ofthe hardcover lst edition 1983
A Division of Plenum Publishing Corporation
233 Spring Street, New York, N.Y. 10013
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted,
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
Preface
The authors' aim is to present a review of experimental and theoretical research
that has been done to establish and to explain the physical properties of actinide
compounds. The book is aimed at physicists and chemists. It was thought
useful to collect a large selection of diagrams of experimental data scattered
in the literature. Experiment and theory are presented separately, with cross
references.
Not all work has been included: rather, typical examples are discussed.
We apologize to all researchers whose work has not been quoted. Since we
report on an active field of research, clearly the data and their interpretation
are subject to change.
We benefitted greatly from discussions with many of our colleagues,
particularly with Drs. G. H. Lander and W. Suski. The help of Mrs. C. Bovey and
Ch. Lewis in the preparation of the manuscript, and the artwork and photo
graphic work of Ms. Y. Magnenat and E. Spielmann of the Institute of Experi
mental Physics of the University of Lausanne, are gratefully acknowledged. Our
particular thanks are due to Ms. J. Ubby for her skillful and patient editorial
work.
We express our thanks to the Swiss National Science Foundation and the
Herbette Foundation of the University of Lausanne, who promoted the
cooperation of the authors.
Contents
list of Tables xi
CHAPTER 1. Introduction 1
CHAPTER 2. Survey of Experimental Data 7
2.1. Experimental Techniques ........................... 7
2.1.1. Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 .2. Neutron Diffraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.3. Nuclear Magnetic Resonance. . . . . . . . . . . . . . . . . . . . . . 9
2.1.4. Mossbauer Resonance .......................... 9
2.1.5. Muon Spin Rotation (~SR) . . . . . . . . . . . . . . . . . . . . . .. 11
2.1.6. Other Experimental Techniques. . . . . . . . . . . . . . . . . . .. 12
2.2. NaCI-Type Metallic Actinide Compounds ..... .'. . . . . . . . . .. 13
2.2.1. General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13
2.2.2. Uranium Monophosphide . . . . . . . . . . . . . . . . . . . . . . .. 16
2.2.3. Uranium Monoarsenide ......................... 22
2.2.4. Uranium Mononitride .......................... 26
2.2.5. Uranium Antimonide . . . . . . . . . . . . . . . . . . . . . . . . . .. 31
2.2.6. Uranium Monochalcogenides . . . . . . . . . . . . . . . . . . . . .. 33
2.2.7. Neptunium Carbide . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36
2.2.8. Neptunium Monopnictides .... . . . . . . . . . . . . . . . . . . . 38
2.2.9. Plutonium Compounds. . . . . . . . . . . . . . . . . . . . . . . . .. 42
2.2.10. Solid Solutions of Uranium Monopnictides and Mono-
chalcogenides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 44
2.3. UX2"Type and UXY-Type Tetragonal Uranium Compounds. . . .. 51
2.4. A3X4-Type Metallic Actinide Compounds. . . . . . . . . . . . . . . .. 58
2.5. Intermetallic Actinide Compounds ..................... 62
2.5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 62
2.5 .2. AX2-Type Intermetallics . . . . . . . . . . . . . . . . . . . . . . . .. 63
2.5.3. AX3-Type Intermetallics . . . . . . . . . . . . . . . . . . . . . . . .. 69
2.5.4. Miscellaneous Intermetallics ...................... 72
vii
viii CONTENTS
2.6. Actinide Oxides ................................. , 74
2.6.1. Uranium Dioxide ............................. 76
2.6.2. U0 -Th0 Solid Solutions ...................... , 79
2 2
2.6.3. Other Uranium Oxides ......................... , 81
2.604. Neptunium Dioxide ........................... , 83
2.6.5. Intermetallic Oxides ........................... 85
2.7. Actinide Halides ................................. 86
2.7.1. Uranium Triiodide ............................ , 86
2.7.2. Other Actinide Halides. . . . . . . . . . . . . . . . . . . . . . . . .. 90
2.8. Other Compounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 91
29. Spectroscopic Data on Actinide Ions ................... , 92
CHAPTER 3. Survey of Theory 99
3.1. Localized Electron Theories ......................... , 99
3.1.1. Assumptions of the Crystal-Field Model .............. 99
3.1.2. Crystal-Field Theory . . . . . . . . . . . . . . . . . . . . . . . . . .. 103
3.1.2a. Mathematical Formulation .................... 105
3.1.2b. The Coulomb Hamiltonian .................... 106
3.1.2c. The Spin-Orbit Hamiltonian .................. , 108
3.1 .2d. The Crystal-Field Hamiltonian . . . . . . . . . . . . . . . . .. 111
3.1 .2e. Point Symmetry .......................... , 113
3.1 .2f. Matrix Elements of JC cf' ..................... , 115
3.1 .2g. The Zeeman Hamiltonian .. . . . . . . . . . . . . . . . . . .. 117
3.1.2h. Thermodynamic Averages. . . . . . . . . . . . . . . . . . . .. 117
3.1 .2i. Shielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 120
3.1 .2j. Comments on the Crystal-Field Theory . . . . . . . . . . .. 121
3.1.3. Interionic Interactions ......................... , 123
3.1.3a. Heisenberg Exchange . . . . . . . . . . . . . . . . . . . . . . .. 123
3.1 .3b. Anisotropic Exchange ....................... 124
3.1.3c. Electric Multipole Interactions ................. , 125
3.1.3d. Biquadratic Exchange. . . . . . . . . . . . . . . . . . . . . . .. 125
3.1.3e. RKKY Exchange .......................... , 125
3.1.3f. Coqblin-Schrieffer Exchange . . . . . . . . . . . . . . . . . .. 129
3.1.4. Theories of First-Order Transitions Based on Localized
Models .................................... 133
3.1Aa. Biquadratic Exchange. . . . . . . . . . . . . . . . . . . . . . .. 133
3.1Ab. Allen's Theory of U02 •.••.•••.•.••••••.•••. , 135
3.1Ac. Theories of Np02 .......................... 142
3.1.4d. The Long-Wang Theory of UP .................. 144
3.1Ae. Blume's Level-Crossing Theory. . . . . . . . . . . . . . . . .. 146
3.1.4f. A Theory of UI3 . • . . . . • . . . • . . . . . . . . . . . . . . .. 147
3.2. Theories Involving Itinerant Electrons .................. , 148
CONTENTS ix
3.2.1. Band Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 149
3.2.1a. Introduction .............................. 149
3.2.1 b. Actinide Metals. . . . . . . . . . . . . . . . . . . . . . . . . . .. 150
3.2.1c. NaCI-Type Actinide Compounds ................ 152
3.2.2. Spin-Fluctuation Models. . . . . . . . . . . . . . . . . . . . . . . .. 155
3.2.3. Electron Delocalization Model. . . . . . . . . . . . . . . . . . . .. 157
3.3. A Theory Intermediate to the Localized and Band Models. . . . .. 164
3.4. Similarities between Mixed-Valence Rare Earths and Metallic
Actinide Compounds ........................ . . . . .. 169
APPENDIX A. Irreducible Tensor Operators ............ 171
APPENDIX B. Magnetic Structures. . . . . . . . . . . . . . . . . . . .. 175
References ........................................ 185
Author Index 199
Subject Index 207
List of Tables
1. The Three Groups of Magnetic Elements, and a List of the Actinide
Elements Together with Their Electronic Configurations outside the
[RnJ Core 2
2. The Major Classes of Actinide Compounds 3
3. Compounds of the Type AX, with the NaCl Structure 14
4. Tetragonal Conductor or Semiconductor Compounds of the Type
AX2 and AXY 52
5. A3X4-Type Compounds of Body-Centered Cubic Structure 59
6. Intermetallic Actinide Compounds of the Type AX2 64
7. Intermetallic Actinide Compounds of the Type AX3 65
8. Selected Properties of Actinide Oxides 75
9. Listing of Actinide Halides 86
10. D2d Spectroscopic Parameters of If+ 93
11. Crystal-Field Parameters and Mean Radii of Actinides 95
12. Observed and Calculated Crystal-Field Splittings of the Ground State
of Np3+ in LaCh 96
13. Slater Integrals Fi and Spin-Orbit Coupling Parameter A for Trivalent
Actinides in LaC13 Host 97
14. Comparison of Experimental and Theoretical Values of the Slater
Integrals Fi and Spin-Orbit Coupling Constant for U3+ Ions in LaCh 97
15. Composition of the Eigenstates of the Lowest-Lying Manifold of
Crystal-Field States of the U3+ Ion, as Observed in LaCl3 Host 109
16. Sternheimer Shielding Factors for Uranium Ions 112
17. General Form of the Crystal-Field Potential for Electrons with I ~ 3 114
18. Anisotropic Interaction Constants for Ce3+ Pairs in LaCl3 and LaBr3 124
19. Theoretical Parameters and Predictions of Allen's Theory of U02 141
20. Parameters of Several Theories of Actinide Spin-Fluctuation Systems 156
xi
CHAPTER 1
Introduction
Most research into the magnetic properties of crystalline solids in the
last forty years has been focused on the iron-group transition metals, the rare
earth metals (such as gadolinium), and the vast number of compounds of these
metals with other elements. It is for the most part only in the last fifteen years
that the third group of magnetic elements, the actinides, have come under
experimental and theoretical investigation (see Table 1). The actinides are
elements with atomic number greater than 89, of which D, Np, and Pu are the
best-known examples. They have many radioactive isotopes requiring special
care in handling. The compounds of actinide elements include metals, semi
conductors, and insulators and fall into the eight broad classes listed in Table 2.
These materials are usually either ferromagnetically or antiferromagnetically
ordered at low temperatures.
Interest in actinide compounds has been stimulated by the observation
of some quite unusual magnetic, electronic, and thermodynamic properties,
the most striking of which are first-order magnetic phase transitions found in
materials belonging to classes one, six, and eight of Table 2. These transitions
involve discontinuous changes in the ordered magnetic moment per actinide
ion as a function of temperature, and some examples are shown schematically
in Fig. 1. The behavior in parts (B) and (C) of Fig. 1 obviously contrasts strongly
with the "normal" Brillouin curve of part (A) observed most often in the iron
and rare earth group compounds where the ordered moment vanishes con
tinuously as T is raised through the Neel temperature TN or the Curie tempera
ture Te. These transitions are associated with the following properties:
«
1). At a certain temperature T' TN or Te), the ordered moment a per
actinide ion decreases continuously by -10% with increasing T. Examples
of compounds exhibiting this "moment-jump" transition are the metals up,l
DAs,2,3 and NpC.4