Molecular Structure and Bonding in Plutonium Carbides: A Theoretical Study of PuC₃

Abstract

The most relevant species of plutonium tricarbide were characterized using theoretical methods. The global minimum is predicted to be a fan structure where the plutonium atom is bonded to a quasi-linear C 3 unit. A rhombic isomer, shown to be a bicyclic species with transannular C−C bonding, lies about 39 kJ/mol above the fan isomer. A linear PuCCC isomer and a three-membered ring CPuC 2 isomer were found to be higher in energy (150 and 195 kJ/ mol, respectively, above the predicted global minimum). The possible processes for the formation of these species are discussed, and the IR spectra were predicted to help in possible experimental detection. The nature of the Pu−C interaction has been analyzed in terms of a topological analysis of the electronic density, showing that Pu−C bonding is essentially ionic with a certain degree of covalent character. 51 out recently. 9−11 An important conclusion from these studies is 52 that the most stable species is not always observed in the 53 experiments. For example, the linear uranium dicarbide 54 observed in the experiments, 6,7 CUC, is not the lowest-lying 55 isomer of uranium dicarbide. The global minimum is predicted 56 to be a C 2v-symmetric (T-shape) U(C 2) isomer, with an energy 57 lying more than 240 kJ/mol lower than that of the linear 58 species. 7,9,10 Recent theoretical studies on uranium dicarbide 59 include the adsorption of the linear and T-shape uranium 60 dicarbide isomers on a graphene surface. 12 Other studies on 61 actinide carbides include a very recent work on NpC, NpC 2 , 62 and NpC 4. 13 63 On the other hand, little is known about the molecular 64 structure of small plutonium carbides. Datta et al. 5 observed 65 PuC n + ions through radio-frequency spark source mass 66 spectrometry studies, but no structural information is available 67 from these experiments. In a recent study by Pogany et al., 14 68 triangular PuC 2 was predicted from theoretical calculations to 69 lie about 381 kJ/mol below CPuC in energy. The molecular 70 structure of PuC 4 has also been theoretically studied in another 71 paper by Pogany et al., 15 which predicted a fan-type structure as 72 the most stable isomer. To the best of our knowledge, no 73 information is available for other plutonium carbides. In the 74 present work, a theoretical study of the next member in this 75 series is provided. The aim of the present work was to

A Systematic Theoretical Study of UC6: Structure, Bonding Nature, and Spectroscopy

“…In most cases, the T1 values do not indicate a strong multireference character of the wave functions, as shown in Table S4. Previous studies 10,22 on actinide carbide compounds have also shown that the results of multiconfigurational calculations are consistent with those of CCSD(T). Our results indicate that the CCSD(T) method predicted a different energy order in comparison to B3LYP.…”

“…The single-point energies were also calculated using coupled cluster theory with single and double excitations and a perturbative triples correction (CCSD­(T)) to obtain a more reasonable energy order for the different isomers. Previous works , have indicated that CCCD­(T) can predict energy order similarly to the multireference configuration interaction (MRCI), and these works have also shown that the spin–orbit coupling (SOC) produces low incremental energy difference. The SOC was not considered to evaluate the energy order for the different isomers in the present work.…”

Theoretical study of actinide monocarbides (ThC, UC, PuC, and AmC)

“…Yet, only four theoretical studies dealt with AnC molecules (UC, 19,20 NpC, 21 and PuC 22 ) until now, providing very limited information on their molecular properties. In contrast, the di-, 21,[23][24][25][26] tri-, 27,28 and tetracarbides 18,20,21,29 of Th, U, Np, Pu, and Am have been quite extensively explored by advanced quantum chemical calculations. The lack of reliable information on the monocarbides is the motivation to our present study in which we apply relativistic multireference and density functional theory (DFT) methods to elucidate the electronic structure and other molecular characteristics of the most important monocarbides (ThC, UC, PuC, and AmC).…”

12-Membered Ring Carbides with Stabilization of Actinide Atoms

“…23 The UC 3 and PuC 3 clusters from global-minimum searching results adopt fan-like structures via the bonding of actinides to the C 3 unit. 24,25 From then on, the actinide tetracarbide clusters (AnC 4 , An: Th, U, Np, Pu, and Am) and actinide hexacarbides (ThC n , UC 6 and PuC 6 , n = 1− 7) have been theoretically predicted to possess a planar sector structure in which actinide atoms are connected to fan-shaped C 4 and C 6 , respectively. 22,26−30 Although a series of gas-phase molecular species, like An m C n + (m = 2, n = 2−18, An = Th, U) have been produced by laser ionization of AnC 4 alloys, only An 2 C 3 and An 2 C 4 have been structurally assigned, 31 atom.…”

“…The ground states for actinide monocarbides have been predicted by relativistic multireference calculations as 3 Σ + , 4 H, 5 H, 7 F, and 3 Σ + for AnC (An: Th, U, Np, Pu, and Am), respectively. , The UC 2 was identified as being a linear CUC molecule and the bent ThC 2 are energetically favored . The UC 3 and PuC 3 clusters from global-minimum searching results adopt fan-like structures via the bonding of actinides to the C 3 unit. , From then on, the actinide tetracarbide clusters (AnC 4 , An: Th, U, Np, Pu, and Am) and actinide hexacarbides (ThC n , UC 6 and PuC 6 , n = 1–7) have been theoretically predicted to possess a planar sector structure in which actinide atoms are connected to fan-shaped C 4 and C 6 , respectively. ,− Although a series of gas-phase molecular species, like An m C n + ( m = 2, n = 2–18, An = Th, U) have been produced by laser ionization of AnC 4 alloys, only An 2 C 3 and An 2 C 4 have been structurally assigned, which contain An–C 2 bonds similar to those in U­(C 2 ) 2 and U­(C 2 ) 3 molecules produced by the reaction of the U atom and carbon atom . Hitherto, except that experiments in gas phase often result in fullerenes, ,− there are no other molecular actinide carbides reported.…”