R.G. Haire

Bio: R.G. Haire is an academic researcher from Oak Ridge National Laboratory. The author has contributed to research in topics: Californium & Einsteinium. The author has an hindex of 8, co-authored 13 publications receiving 197 citations.

Absorption spectrophotometric and x-ray diffraction studies of the trichlorides of berkelium-249 and californium-249

Abstract: Absorption spectrophotometric and X-ray powder diffraction methods have been applied to a study of the trichlorides of /sup 249/Bk and /sup 248/Cf and their relationship through the ..beta.. decay of /sup 249/Bk. BkCl/sub 3/ has been prepared for the first time in the PuBr/sub 3/-type orthorhombic modification by quenching from the melt. Each of the crystal forms (UCl/sub 3/-type hexagonal and PuBr/sub 3/-type orthorhombic) of BkCl/sub 3/ and CfCl/sub 3/ has been characterized on the basis of its solid-state absorption spectrum. The orthorhombic forms of BkCl/sub 3/ and CfCl/sub 3/ are the high-temperature modifications with respect to the hexagonal phases, with the apparent transition temperatures near the melting points of BkCl/sub 3/ (876 K) and CfClnumber (818 K). Orthorhombic BkCl/sub 3/ transmutes to orthorhombic CfCl/sub 3/ and hexagonal BkCl/sub 3/ transmutes to hexagonal CfCl/sub 3/. Thus, it was found that both the oxidation state and the crystal structure of the parent /sup 249/Bk compound were retained by the daughter /sup 249/Cf compound through ..beta.. decay in the bulk phase solid state. 11 references, 5 figures.

Chemical consequences of radioactive decay. 1. Study of californium-249 ingrowth into crystalline berkelium-249 tribromide: a new crystalline phase of californium tribromide

Abstract: Spectrophotometric and x-ray powder diffraction methods have been applied to a study of the ingrowth of californium-249 by ..beta../sup -/ decay of berkelium-249 in crystalline /sup 249/BkBr/sub 3/. It was found that the Cf daughter grows in with the same oxidation state and crystal structure as the parent. Thus, six-coordinate BkBr/sub 3/ (AlCl/sub 3/-type monoclinic structure) generates six-coordinate CfBr/sub 3/, and eight-coordinate BkBr/sub 3/ (PuBr/sub 3/-type orthorhombic structure) generates eight-coordinate CfBr/sub 3/, a previously unknown form of CfBr/sub 3/. It was also found that the daughter Cf(III) in the BkBr/sub 3/ parent compound can be reduced to Cf(II) by treatment with H/sub 2/, as it can in pure CfBr/sub 3/. 5 figures.

Key Elements in the Structure and Function Relationship of the MgCl2/TiCl4/Lewis Base Ziegler−Natta Catalytic System

Abstract: We present a theoretical study of the basic interactions occurring at supported hetereogenous Ziegler−Natta catalytic systems. We first investigated the interaction between prototypes of each class of industrially relevant internal donors (1,3-diethers, alkoxysilanes, phthalates, succinates) and the MgCl2 support. Our analysis indicates that donors can be separated into two classes. 1,3-Diethers and alkoxysilanes belong to the former because they have a short spacer between the coordinating O atoms and coordinate preferentially to the same Mg atom of the (110) lateral cut. Conversely, phthalates and succinates belong to the latter class because they have a longer spacer between the coordinating O atoms and thus can adopt a variety of coordination modes. Indeed, they can coordinate to both the (100) and (110) lateral cuts. In the last part of this manuscript we report on the stereo- and regioselective behavior of possible active Ti species with and without two succinate molecules coordinated in the proximi...

Electronic structure and ionicity of actinide oxides from first principles

Abstract: The ground-state electronic structures of the actinide oxides $A\text{O}$, ${A}_{2}{\text{O}}_{3}$, and $A{\text{O}}_{2}$ ($A=\text{U}$, Np, Pu, Am, Cm, Bk, and Cf) are determined from first-principles calculations, using the self-interaction corrected local spin-density approximation. Emphasis is put on the degree of $f$-electron localization, which for $A{\text{O}}_{2}$ and ${A}_{2}{\text{O}}_{3}$ is found to follow the stoichiometry, namely, corresponding to ${A}^{4+}$ ions in the dioxide and ${A}^{3+}$ ions in the sesquioxides. In contrast, the ${A}^{2+}$ ionic configuration is not favorable in the monoxides, which therefore become metallic. The energetics of the oxidation and reduction in the actinide dioxides is discussed, and it is found that the dioxide is the most stable oxide for the actinides from Np onward. Our study reveals a strong link between preferred oxidation number and degree of localization which is confirmed by comparing to the ground-state configurations of the corresponding lanthanide oxides. The ionic nature of the actinide oxides emerges from the fact that only those compounds will form where the calculated ground-state valency agrees with the nominal valency expected from a simple charge counting.

Emergence of californium as the second transitional element in the actinide series

Abstract: A break in periodicity occurs in the actinide series between plutonium and americium as the result of the localization of 5f electrons. The subsequent chemistry of later actinides is thought to closely parallel lanthanides in that bonding is expected to be ionic and complexation should not substantially alter the electronic structure of the metal ions. Here we demonstrate that ligation of californium(III) by a pyridine derivative results in significant deviations in the properties of the resultant complex with respect to that predicted for the free ion. We expand on this by characterizing the americium and curium analogues for comparison, and show that these pronounced effects result from a second transition in periodicity in the actinide series that occurs, in part, because of the stabilization of the divalent oxidation state. The metastability of californium(II) is responsible for many of the unusual properties of californium including the green photoluminescence.

Crystal chemical incorporation of high level waste species in aluminotitanate-based ceramics: Valence, location, radiation damage, and hydrothermal durability

Abstract: A compilation is made of the crystallographic mechanisms whereby (simulated) radwaste species are incorporated in the “synroc” phases zirconolite, perovskite, hibonite, and “hollandite.” From these data and consideration of the crystal chemical criteria of valence and effective ionic radii, the most probable host phases for transuranic isotopes are identified. The distinction is drawn between incorporation of radwaste species as dilute homogeneous, continuous solid solutions and as heterogeneous, noncontinuous solid solutions. It is shown that compositional variations at the nanometer level are frequently accompanied by the generation of new interstices within extended defects, which are suitable for the location of radwaste. Nuclides that are unstable towards beta and gamma decay lead to transmutation-induced changes in stoichiometry. Crystallochemical mechanisms that minimize structural disruption during the formation of radiogenic species are discussed. Thermally promoted recovery of metamict phases, which were rendered aperiodic by direct atomic displacements of alpha-recoil nuclei, are examined in terms of recrystallization via the hierarchial arrangement of space groups. An evaluation is made of the hydrothermal durability of synroc phases under conditions likely to be experienced by the wasteform should the repository be breached by groundwaters shortly after disposal.

Characterization of berkelium(III) dipicolinate and borate compounds in solution and the solid state

Abstract: INTRODUCTION Developing the chemistry of late actinides is hindered by the lack of availability of isotopes, the need for specialized research facilities, and the nuclear instability of the elements. Berkelium represents one of the last elements that can be prepared on a milligram scale in nuclear reactors. However, its only available isotope, 249 Bk, has a half-life of only 320 days, which has greatly curtailed the expansion of its chemistry and fundamental exploration of how large relativistic and spin-orbit coupling effects alter its electronic structure. Furthermore, data gathered from Bk(III) in aqueous media suggest that its coordination may be different from that of earlier actinides. However, a single-crystal structure of a berkelium compound has remained elusive, leaving unanswered whether these structural changes occur in the solid state. RATIONALE This work focuses on characterizing two distinct berkelium compounds on the milligram scale. In particular, the goal was to obtain crystals of these compounds that could be used in structure determinations and physical property measurements. Two compounds were selected: a coordination complex of dipicolinate and a borate. Dipicolinate complexation occurs with most other lanthanides and actinides in the +3 oxidation state, facilitating comparisons across the series to discern periodic trends. In the borate family, the structural frameworks are hypersensitive to the nature of the bonding at the metal center and are rearranged accordingly. Modeling the experimental data using a variety of computational techniques allows us to deconvolute the role of covalent bonding and spin-orbit coupling in determining the electronic properties of berkelium. RESULTS Experiments with milligram quantities of 249 Bk were choreographed for 6 months before the arrival of the isotope because the total quantity used in the studies was 13 mg, which corresponds to a specific activity of 21 Ci. Although this isotope is a low-energy β emitter, it decays to 249 Cf at a rate of about 1.2% per week, and the latter produces hard γ radiation that represents a serious external hazard. In addition, the samples described in this work undergo about 10 12 decays per second. This rapid decomposition necessitated the development of techniques for swiftly preparing and encapsulating samples and for collecting all structural and spectroscopic data within 24 hours of crystal formation. After this preparation, the single-crystal structures of Bk(III)tris(dipicolinate) and Bk(III) borate were determined. The latter compound has the same topology as that of californium(III) (Cf) and contains an eight-coordinate BkO 8 unit. This reduction in coordination number is consistent with previous solution-phase x-ray absorption measurements and indicates that a drop in coordination number in the actinide series from nine to eight begins at berkelium. The magnetic and optical properties of these samples were also measured. The red luminescence from Bk(III) was similar in nature to that of curium(III) and is primarily based on an f - f transition. The ingrowth of the broad green luminescence from Cf(III), which is caused by a ligand-to-metal charge transfer, was shown to be distinct in nature from that originating from Bk(III). Ligand-field, density functional theory, and wave-function calculations were used to understand the spectroscopic features and revealed that the single largest contributor to the unexpected electronic properties of Bk(III) is spin-orbit coupling. This effect mixes the first excited state with the ground state and causes a large deviation from a pure Russell-Saunders state. The reduction in the measured magnetic moment for these samples from that calculated for an f 8 electron configuration is primarily attributable to this multiconfigurational ground state. CONCLUSION The crystallographic data indicate that Bk(III) shares more structural similarities with Cf(III) than with Cm(III). However, ligand-field effects are more similar between Bk(III) and Cm(III). Terbium (Tb), in the lanthanide series, represents the closest analog of Bk because the trivalent cations possess 4 f 8 and 5 f 8 configurations, respectively. Spin-orbit coupling in Bk(III) creates mixing of the first excited state ( 5 G 6 ) with the ground state. In contrast, the ground state of the Tb(III)tris(dipicolinate) contains negligible contributions of this type. An overall conclusion from this study is that spin-orbit coupling plays a large role in determining the ground state of late actinide compounds.