Pressure-induced evolution of crystal and electronic structure of neptunium hydrides.

An extensive exploration of high-pressure phase diagrams of NpH ( = 1-10) compounds was performed by using swarm-intelligence-based CALYPSO structure searches. We propose five stable hydrogen-rich clathrate phases (4/-NpH, -NpH, 3̄-NpH, 6/-NpH, and 3̄-NpH) that are composed of unusual H cages with stoichiometries H, H, H, and H in which the H atoms are weakly covalently bonded to one another, with neptunium atoms occupying centers of the cages. The electronic structure analyses show that these predicted hydrogen-rich structures are all metallic phases, and Np-H and H-H bonds are formed by ionic and covalent bond interactions, respectively.

Intermediates of Carbon Monoxide Oxidation on Praseodymium Monoxide Molecules: Insights from Matrix-Isolation IR Spectroscopy and Quantum-Chemical Calculations.

Identifying reaction intermediates in gas-phase investigations will provide understanding for the related catalysts in fundamental aspects including bonding interactions of the reaction species, oxidation states (OSs) of the anchored atoms, and reaction mechanisms. Herein, carbon monoxide (CO) oxidation by praseodymium monoxide (PrO) molecules has been investigated as a model reaction in solid argon using matrix-isolation IR spectroscopy and quantum-chemical calculations. Two reaction intermediates, OPr(η-CO) and OPr(η-CO), have been trapped and characterized in argon matrixes.

Metallic and anti-metallic properties of hydrogen adsorbed AnO (An = Th, U, and Pu) surfaces.

The effect of atomic hydrogen adsorption on AnO2 (An = Th, U, and Pu) surfaces is studied in the framework of density functional theory and Hubbard-corrected density functional theory. Several adsorption coverages (1/3, 1/2, 2/3, and 1 monolayer) are considered. For the band insulator ThO2, surface metallicity induced by hydrogen adsorption is observed due to the electron donation of the hydrogen to the surface.

FBMF (M = V, Nb, and Ta) and FBMF (M = Nb and Ta): A Combined Matrix Isolation Infrared Spectroscopic and Quantum Chemical Investigation.

Through matrix isolation infrared spectrometry and quantum chemical calculations, the reactions of laser ablated V, Nb, and Ta with boron trifluoride were investigated in excess solid neon at 4 K. The possible reaction products FBMF, FBMF, and BMF (M = V, Nb, and Ta) were calculated at the B3LYP, BPW91, and CCSD(T) levels of theory. The B-M bond strength in FBMF molecules is confirmed by energy decomposition analysis-natural orbitals for chemical valence calculations, CASSCF calculation, and natural bond orbital analysis, which favors one σ bond and two half π bonds.

Pressure-Stabilized Zinc Trifluoride.

By combining the particle swarm optimization algorithm with first-principles calculation, the high-pressure phase diagram of Zn-F binary compounds was established. An unexpected stoichiometry of ZnF with space group is thermodynamically stable above 183 GPa. The new structure is fascinating with the appearance of Zn[F] units.

A first-principles study on hydrogen distributions in the α-U/UO interface.

We investigate the distribution preference of hydrogen in the α-U/UO interface by using the DFT+U method. We find that a monolayer of hydrogen atoms firstly assembles right in the interface between α-U and UO. Through detailed electronic state analysis, it is revealed that the formation of U-H bonds with uranium atoms at the UO side favors this hydrogen atom assembly.

Theoretical prediction of some layered PaO phases: structure and properties.

Density functional theory (DFT) was used to predict and study protactinium pentoxide (PaO), which presents a fluorite and layered protactinium oxide-type structure. Although the layered structure has been observed with the isostructural transition Nb and Ta metal pentoxides experimentally, the detailed structure and properties of the layered PaO are not clear and understandable. Our theoretical prediction explored some possible stable structures of the PaO stoichiometry according to the existing MO structures (where M is an actinide Np or transition Nb, Ta, and V metal) and replacing the M ions with protactinium ions.

Dependency of f states in fluorite-type XO (X = Ce, Th, U) on the stability and electronic state of doped transition metals.

Fluorite-type XO2 (X = Ce, Th, U) have versatile technological and industrial applications, and the behavior of impurities in the oxides is one of the engaging topics for their application. However, the fundamental behaviors of impurities are still lacking. Herein, we conduct a systematic first-principles DFT+U screening to find the trends of transition metal (TM) behaviors in the three dioxides in terms of energetics and electronic states, with a particular focus on the dependency of f electronic states of the hosts.

Electronic Structure and Chemical Bonding of [AmO(HO) ].

Systematic americyl-hydration cations were investigated theoretically to understand the electronic structures and bonding in [(AmO)(HO) ] ( = 1-6). We obtained the binding energy using density functional theory methods with scalar relativistic and spin-orbit coupling effects. The geometric structures of these species have been investigated in aqueous solution via an implicit solvation model.

Metallization and positive pressure dependency of bandgap in solid neon.

The metallization of neon remains a controversial problem as there is no consensus in theoretical simulations and no experimental verification. In this work, the insulator-to-metal transition in fcc solid neon at high pressure was revisited with a coupling of the all-electron full-potential linear augmented-plane wave (FP-LAPW) method and the GW correction to avoid the potential unreliability of pseudopotential under high pressure and correct the inaccurate energy gaps caused by local density or generalized gradient approximation of the exchange-correlation. This FP-LAPW + GW calculation predicts that the bandgap closes at a density of 88.

Phase Segregation, Transition, or New Phase Formation of Plutonium Dioxide: The Roles of Transition Metals.

As impurities are virtually impossible to exclude from Pu oxides in realistic environments, understanding the roles of impurities is crucial for the applications and designs of Pu oxides. Here we perform a systematic first-principles DFT + U calculation to find the trends of transition-metal (TM) behaviors in PuO in terms of energetics, atomic properties, oxidation states, and electronic structures. The results show that group IV-B elements Ti, Zr, and Hf are energetically and electronically favorable in PuO and render the possibilities of forming Pu-TM-O ternary phases.

Unraveling the highest oxidation states of actinides in solid-state compounds with a particular focus on plutonium.

The nature and extent of the highest oxidation state (HOS) in solid-state actinide compounds are still unexplored compared with those of small molecules, and there is burgeoning interest in studying the actinide-ligand bonding nature in the condensed state. A comprehensive understanding of the electronic structure and unraveling the possibility of a HOS are of paramount importance in solid-state actinide chemistry. Here, we report the physical OS of the early to middle actinides (Th → Cm) in solid-state compounds via a more rigorous quantum mechanical definition of OS under the DFT+U theoretical frameworks for the first time.

Theoretical studies on the oxidation states and electronic structures of actinide-borides: AnB (An = Th-Cm) clusters.

As B12 clusters exhibit significant structural stability due to double aromaticity, metal doped-B12 clusters often prefer a half sandwich structure. Herein, we report a systematic theoretical study on the geometric and electronic structures, and chemical bonding of the half sandwich AnB12 (An = Th to Cm) clusters to explore the stability and extent of covalency of the An-B bonds of these actinide borides. We have shown that in the gas-phase clusters, the significant stability of AnB12 is determined by electrostatic and orbital interactions between the An 5f6d7s orbitals and π-type molecular orbitals from B 2p orbitals of the B12 unit.

Correction: Insights into the enhanced Ce[triple bond, length as m-dash]N triple bond in the HCe[triple bond, length as m-dash]N molecule.

Correction for 'Insights into the enhanced Ce[triple bond, length as m-dash]N triple bond in the HCe[triple bond, length as m-dash]N molecule' by Zhen Pu et al., Phys. Chem.

Ammonia Activation by Ce Atom: Matrix-Isolation FTIR and Theoretical Studies.

The activation of ammonia by cerium atom has been investigated in solid argon using infrared spectroscopy and density functional theoretical calculations. The results reveal that the spontaneous formation of CeNH complex on annealing is the initial step in the reactions of cerium atoms with ammonia. The CeNH complexes rearrange to generate the inserted HCeNH molecules on irradiation.

Stability and optical properties of plutonium monoxide from first-principle calculation.

The resolution of questions about the existence of condensed plutonium monoxide (PuO) has long been hindered by lack of thermochemical data. Here we perform first-principles calculation to investigate the reaction PuO + Pu → 3 PuO and find that PuO is thermodynamically unstable under ambient pressure. We also find that pressure could stabilize PuO by strengthening the hybridization between Pu-5f/6d and O-2p states.

Insights into the enhanced Ce[triple bond, length as m-dash]N triple bond in the HCe[triple bond, length as m-dash]N molecule.

Herein, an experimental study of the vibrational spectra of HCeN was carried out in solid argon, followed by theoretical investigations of molecular structures and the nature of Ce[triple bond, length as m-dash]N bond. The absorption band at 937.7 cm with the 1.