Actinide Materials Research Supported by the Office of Basic Energy Sciences, U.S. Department of Energy
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Actinide Materials Research Supported by the Office of Basic Energy Sciences, U.S. Department of Energy Lester R. Morss Chemical Sciences, Geosciences, and Biosciences Division Office of Basic Energy Sciences (BES), U.S. Department of Energy (DOE) Washington, DC 20585, U.S.A. ABSTRACT The fundamental research topic in actinide chemistry and materials sciences is the role that the 5f electrons play in bond formation, which provides the central focus for DOE BESsupported actinide science. Structural systematics of the actinide metals, oxides, and other compounds as a function of atomic number are well established. Magnetic measurements have shown that the light actinide metals have delocalized 5f orbitals (i.e., the 5f electrons form bands), whereas the f electrons become localized at americium. Thus, the magnetic behavior of the first part of the actinide series resembles that of the d transition metals whereas the heavier actinides exhibit behavior similar to the rare earth metals. Spectroscopic results have established electronic energy levels, crystal field splitting, and near-neighbor coordination. The 5f orbitals participate in the band structure of materials that contain the light actinide metals and some of their intermetallic compounds, and perhaps in molecular compounds. Molecular-level information on the geometry and bonding in solids, at surfaces, and in clusters can now be obtained at BESsupported facilities. INTRODUCTION During the Manhattan Project, Glenn Seaborg elaborated the concept that the radioactive group of elements heavier than actinium represented a new “actinide series” that gradually filled the 5f subshell [1,2]. Fundamental understanding of the electronic properties of the transuranium elements during the 1940s was essential to the identification, characterization, separation, and utilization of these elements. The US Atomic Energy Commission (AEC), which came into being on January 1, 1947, was given the responsibility to carry out a diversified program of basic research “to assist in the acquisition of an ever expanding fund of theoretical and practical knowledge” in atomic, nuclear, and radiation physics, and in related disciplines of chemistry and applied mathematics. Even the earliest organization charts of the AEC showed a box entitled “Division of Research”[3]. An important part of the mission of the AEC was to continue to support the research, initiated during the wartime Manhattan Project, into the unique nature of the actinide elements. The Office of Science of the U.S. Department of Energy (DOE) now fulfills this fundamental research mission. Within the Office of Science, the Office of Basic Energy Sciences (BES) carries out programs of fundamental energy-related research in materials sciences and engineering, chemistry, geosciences, and molecular biosciences. As part of this mission, BES continues the tradition of over 60 years of support of research that has established the scientific principles behind the physical and chemical behavior of actinide elements and their co
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