The Actinides: Electronic Structure and Related Properties

369 Pages·1974·8.24 MB·English

by  A.J. Freeman (Eds.)

M A T E R I A LS S C I E N CE A ND T E C H N O L O GY
EDITORS
ALLEN M. ALPER JOHN L. MARGRAVE A. S. NOWICK
GTE Sylvania Inc. Department of Chemistry Henry Krumb School
Precision Materials Group Rice University of Mines
Chemical & Metallurgical Houston, Texas Columbia University
Division New York, New York
Towanda, Pennsylvania
A. S. Nowick and B. S. Berry, ANELASTIC RELAXATION IN CRYSTALLINE SOLIDS,
1972
£. A. Nesbitt and J. H. Wernick, RARE EARTH PERMANENT MAGNETS, 1973
W. E. Wallace, RARE EARTH INTERMETALLICS, 1973
/. C. Phillips, BONDS AND BANDS IN SEMICONDUCTORS, 1973
H. Schmalzried, SOLID STATE REACTIONS, 1974
Λ H. Richardson and R. V. Peterson (editors), SYSTEMATIC MATERIALS ANALYSIS,
VOLUMES I AND II, 1974. Volume III in preparation
A.J. Freeman and J. B. Darby, Jr. (editors), THE ACTINIDES: ELECTRONIC STRUC­
TURE AND RELATED PROPERTIES, VOLUMES I AND II, 1974
In preparation
A. S. Nowick andJ. J. Burton (editors), DIFFUSION IN SOLIDS: RECENT DEVELOP­
MENTS
7. W. Matthews (editor), EPITAXIAL GROWTH
THE ACTINIDES
ELECTRONIC STRUCTURE AND RELATED PROPERTIES
Edited by A. J. FREEMAN
Department of Physics
Northwestern University
Evanston, Illinois
and
Argonne National Laboratory
Argonne, Illinois
J. B. DARBY, JR.
Materials Science Division
Argonne National Laboratory
Argonne, Illinois
VOLUME I
1974
ACADEMIC PRESS
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LIBRARY OF CONGRESS CATALOGING IN PUBLICATION DATA
Freeman, Arthur J
The actinides: electronic structure and related
properties.
(Materials science series)
Includes bibliographies.
1. Actinide elements. I. Darby, Joseph Branch,
Date joint author. II. Title.
QD172.A3F73 546'.4 73-18970
ISBN 0-12-266701-8 (v. 1)
PRINTED IN THE UNITED STATES OF AMERICA
List of Contributors
Numbers in parentheses indicate the pages on which the authors' contributions begin.
A. T. ALDRED (109), Materials Science Division, Argonne National
Laboratory, Argonne, Illinois
S.-K. CHAN (1), Max-Planck-Institut fur Biophysikalische Chemie,
Gottingen, Germany
B. D. DUNLAP (237), Solid State Sciences Division, Argonne National
Laboratory, Argonne, Illinois
F. Y. FRADIN (181), Materials Science Division, Argonne National
Laboratory, Argonne, Illinois
A. J. FREEMAN (51), Department of Physics, Northwestern University,
Evanston, Illinois
G. M. KALVIUS (237), Physik Department, Technische Universitat
Miinchen, Garching, Germany
D. D. KOELLING (51), Solid State Sciences Division, Argonne National
Laboratory, Argonne, Illinois
D. J. LAM (1, 109), Materials Science Division, Argonne National
Laboratory, Argonne, Illinois
G. H. LANDER (303), Materials Science Division, Argonne National
Laboratory, Argonne, Illinois
Μ. H. MUELLER (303), Materials Science Division, Argonne National
Laboratory, Argonne, Illinois
MICHAEL V. NEVITT (xvii), Office of the Director, Argonne National
Laboratory, Argonne, Illinois
ix
Preface
The last two decades have witnessed remarkable advances in our under
standing of the electronic structure and properties of a wide range of
materials. Sparked by the introduction and use of highly sophisticated experi
mental techniques, a mass of experimental knowledge has emerged that
challenged previous (and oftentimes simplified) theoretical models and
brought about a more unified view of electronic structure and behavior. First
the noble metals, then the transition metals and their compounds, and, more
recently, the rare earths have each enjoyed a period of research on their
electronic structure and properties that achieved a high degree of sophisti
cated understanding previously thought improbable. A similar period has
most recently arrived for actinide research—called, for many reasons and
only somewhat euphemistically, the "last frontier"—on the electronic struc
ture of materials. Until recently, the difficult problems of obtaining samples
of sufficient purity and overcoming problems associated with their radio
active nature have resulted in slow progress and limited understanding.
As is pointed out in the Historical Introduction, research on the electronic
structure of the actinides began in the 1940's with the onset of the Atomic
Age and has continued unabated by a small community of scientists who
have maintained, on an international scale, a continuous and well-documented
flow of new knowledge on the subject. However, it is only within the past
five years that the more intensive effort on experimental studies of a variety
of actinide metals and compounds has fostered intensive theoretical study of
the basic phenomena and has given rise to a more unified understanding of
their electronic properties. These volumes stem from the recognition that
these recent advances have been so pervasive that they require a unified
presentation in a single vehicle.
The actinides have their own unique position among the elements. This
arises from an unusual set of circumstances. In the transition elements, the
s and d valence electrons form conduction bands that are responsible for
their electric, magnetic, and optical properties. The rare earths are unique
in that their 4f electrons are so highly localized, that although they determine
the various exotic magnetic structures and properties of their metals, they
xi
xii PREFACE
have little effect on other chemical and physical behavior that arises from
the transition metal-like structure of their 5d and 6s valence electrons. The
5f electrons in actinide elements are not as well localized as the 4f's in rare
earths but do have energies that are close to those of the 6d and 7s
electrons. This produces, in actinide solids, the unusual condition of a strong
"competition" between the 5f electrons and the 6d and 7s electrons in
determining their electronic structure and properties. The contrast between
the results on the actinides and those on transition and rare-earth metals
makes clear that the 5f electrons are a unique species. Obviously much work
still lies ahead before one will fully understand the behavior of actinides in
detail. The present volumes will, it is hoped, stimulate and encourage con
tinued efforts toward this goal.
The present two-volume work is the first attempt to record and review,
in a comprehensive way, the pertinent information and the existing body of
knowledge on the electronic structure of the actinide elements, alloys, and
compounds from the beginning to the time of completion of the manu
script. Key topics closely allied and, to some extent, inseparable from
electronic structure have also been included. The work includes a critical
assessment of the existing knowledge of the topics reviewed within a frame
work that hopefully will be useful to scientists intimately involved in the
field as well as to the newcomer.
The pattern of the two volumes is as follows. Volume I begins with an
Historical Introduction on actinide research followed by a chapter on crystal-
field theory that discusses the behavior of 5f electrons in actinide compounds
when exposed to strong crystal-field interactions, with emphasis on the
strong intraatomic correlation between electrons. Chapter 2 describes the
present state of knowledge of the electronic energy band structure of the
actinide metals, as derived from energy band theory, with emphasis on the
importance of coulomb correlation in determining the itinerancy (in light
actinides) or localization (in the heavy actinides) of the 5f electrons. The
magnetic properties of the actinide compounds are related to their electronic
structure in Chapter 3. The experimental results, obtained primarily from
magnetic susceptibility data, are presented and used to characterize and
systematize the magnetic properties of ionic, covalent, and intermetallic
compounds. The remaining three chapters of Volume I analyze and critically
review the information on the microscopic electronic properties of metals
and compounds obtained from nuclear magnetic resonance, electron para
magnetic resonance, Mossbauer effect (or nuclear gamma resonance), nuclear
orientation, perturbed angular correlation, and neutron-scattering studies.
Chapter 4 presents Knight-shift and spin-lattice relaxation results that docu
ment our knowledge and understanding of the wide range of magnetic
behavior exhibited by the 5f electrons. The power and limitations of hyperfine
PREFACE xiii
interaction measurements by nuclear radiation in the actinides is brought
into sharp focus in Chapter 5, as is the increased understanding of 5f electron
behavior under various conditions. Finally, Chapter 6 reviews the unique
contribution made to date by slow neutron-scattering experiments and
suggests the increased understanding that the use of this technique will bring
to the actinides in the future.
Chapter I of Volume II (by H. L. Davis) demonstrates how electronic
band-structure calculations have contributed to the fundamental under­
standing of diverse physical properties of the AX compounds. In contrast to
the approach taken in Chapter 1, Volume I, this approach emphasizes a
degree of itinerancy for the 5f electrons of the lighter actinides. Many
electron effects are treated in Chapter 2 (by S. Doniach) using basic many-
body concepts to describe magnetism in the metals, dilute alloys, and inter­
metallic compounds. Optical experiments, as electronic structure probes, to
obtain mappings of the occupied and empty electronic density of states are
described in Chapter 3 (by B. W. Veal). The crystal chemistry of the actinide
compounds, as a linkage between electronic structure and crystal structure,
is treated in Chapter 4 (by D. J. Lam, J. B. Darby, Jr., and Μ. V. Nevitt) and
also includes a comprehensive list of compounds, as well as a description
and classification of crystal structure data. Transport properties and their
relation to electronic structure and magnetic effects are reviewed in Chapter 5
(by Μ. B. Brodsky, A. J. Arko, A. R. Harvey, and W. J. Nellis), and
magnetization studies are described in Chapter 6 (by W. J. Nellis and Μ. B.
Brodsky) for the pure metals, alloys, and compounds that exhibit metallic
behavior. The ultrasonic measurements, valuable in the studies of various
temperature and pressure-induced phase transformations in actinide
materials, is the subject of Chapter 7 (by E. S. Fisher). Volume II closes with
Chapter 8 (by W. P. Ellis) that describes the significant improvements in the
experimental techniques for studying surfaces and surface reactions and the
present status and future promise of surface science as a rapidly emerging
field of actinide research.
The authors are to be commended for the extensive effort expended in
gathering and presenting the information that appears in these volumes.
We also wish to acknowledge the enthusiastic support and encouragement
of numerous associates at Argonne National Laboratory, including
Drs. B. R. T. Frost, Μ. V. Nevitt, N. L. Peterson, and P. G. Shewmon; and
the editorial assistance of Ms. M. F. Adams and the secretarial assistance
of Ms. B. L. Heramb.
Contents of Volume II
Band Structure of Actinide Compounds Possessing NaCl-Type Symmetry
H. L. Davis
Many Electron Effects in the Actinides
S. Doniach
Optical Properties and Electronic Structure of the Actinides
B. W. Veal
The Crystal Chemistry of Actinide Compounds
D. J. Lam, J. B. Darby, Jr., and Μ. V. Nevitt
Transport Properties
Μ. B. Brodsky, A. J. Arko, A. R. Harvey, and W. J. Nellis
Magnetic Properties
W. J. Nellis and Μ. B. Brodsky
Ultrasonic Waves in Actinide Metals and Compounds
E. S. Fisher
Surface Studies
Walton P. Ellis
XV
Historical Introduction*
MICHAEL V. NEVITT
ARGONNE NATIONAL LABORATORY
ARGONNE, ILLINOIS
A review of the historical aspects of research on the actinide metals
reveals that scientists provided, from the earliest years, a legacy of commit­
ment to the understanding of electronic structure. Availability of materials
and experimental difficulties limited the rate of generation of information,
especially during the decade and a half after the first discovery of man-made
elements, but the experimentalist and the theoretician showed no hesitancy
in seeking answers to difficult fundamental questions regarding electron
energies and electron-transport mechanisms.
As an early example of this commitment, we can cite Η. M. Finniston's
1957 comment (Coffinberry and Miner, 1961, p. 82) on the program of
basic research on plutonium in the United Kingdom:
Many of the peculiarities that are so evident in this metal are due to the electronic
characteristics of the plutonium atom, and a theoretical study of the electronic
structure of plutonium is being undertaken, as well as experimental researches that
will give better understanding of electronic behavior.
Initial work on the physical metallurgy of plutonium, the first trans­
uranium metal to be studied in detail, included in almost every laboratory
the measurement of physical properties related to electrons and electronic
energy levels. The following list indicates approximate starting times for
early metallurgical research, which included physical-properties studies
(Coffinberry and Miner, 1961, pp. 1-5), at some of the major research centers:
Canada: Chalk River, 1947
France: Fontenay-aux-Roses, 1956
Union of Soviet Socialist Republics: before 1955
* Work performed under the auspices of the U.S. Atomic Energy Commission.
xvii
xviii MICHAEL V. NEVITT
United Kingdom: AERE Harwell, 1946; AWRE Aldermaston, 1951
United States: Argonne National Laboratory, 1954; Los Alamos
Scientific Laboratory, 1944; Mound Laboratory, 1956.
A review of the progress in the study of the electronic structure of the
actinides is facilitated by the fact that the work has been conducted by a
relatively small community of scientists, who have been generally well
known to each other and who have maintained a stable, well-documented
international forum for summary reporting of their observations, conclu­
sions, speculations, and plans. The forum to which we refer is the series of
international conferences held in 1957,1960,1965, and 1970(Coffinberry and
Miner, 1961; Grison et al, 1961; Kay and Waldron, 1967; Miner, 1970) on
plutonium and, most recently, other actinides. These conferences and their
proceedings are in no sense complete accounts of the published work; how­
ever, they serve as valuable 5-yr markers in a brief historical review.
Looking back on 1960 as a milestone for a first decade of progress, we
may agree with Schonfeld in his statement at the second conference (Grison
et al, 1961, p. 91) that, "... plutonium metallurgy is coming of age (and)...
we are beginning to see serious efforts made to understand its many
pecularities." At the time of the second conference, the now familiar electrical-
resistivity anomaly in α-plutonium was mapped out by Lee et al (Grison
et al, 1961, pp. 39-50) and by Sandenaw and Olsen (Grison et al, 1961,
pp. 59-79). The low-temperature magnetic susceptibility of α-plutonium had
been determined [Lee et al (Grison et al, 1961, pp. 39-50) and Weil et al
(Grison et al, 1961, pp. 104-105)], although its modest temperature sen­
sitivity at low temperatures could not be related to the resistivity behavior.
This problem remains unsolved. Initial measurements of low-temperature
specific heat of plutonium metal were reported, but later work was required
to clarify experimental uncertainties. No unifying theory for the electronic
structure of any of the allotropic forms of plutonium had appeared, even in
embryonic form.
The need for high-purity samples was recognized, and an early indication
of the future availability of high-purity plutonium was provided by
Blumenthal and Brodsky (Grison et al, 1961, pp. 171-186). Knowledge of
alloying behavior as influenced by electronic factors was in an imperfect state,
with only broad generalizations in terms of valency and atomic size being
formulated by Waber and Gschneidner (Grison et al, 1961, pp. 109-134).
The next half decade, ending with the third conference (Kay and Waldron,
1967) was one in which significant advances were made in the range and
accuracy of electronic property measurements, but in which the scope of
interest in the synthetic elements had not extended significantly beyond
plutonium. An essentially smooth and reproducible temperature dependence