First-Principles Study of Adsorption of Actinide Complexes on Borophene

Two- and three-dimensional materials can be used for the sensitive detection of adsorbates through charge-transfer mechanisms. Recently, a two-dimensional borophene material was synthesized in two distinct phases: line-defected planar and buckled. Here, we determine whether borophene can act as a competitive radioactive material sensor by using first-principles calculations to simulate the adsorption of actinide (uranium─U, neptunium─Np, and plutonium─Pu) complexes. Specific ligands are used (OH–, NO3–, CO32–) to generate model actinide complexes representing realistic environmental conditions. Various adsorption configurations are studied for each phase, and the corresponding adsorption energies, charge transfer, and electronic properties are reported. The calculated results reveal the presence of strong interactions due to the formation of a chemical bond between borophene and the oxo ligand of the adsorbate. Periodic trends are established, which indicate the strong affinity to Pu complexes in comparison to Np and U and that complexes containing carbonate bind more strongly overall. We find that the buckled phase engages in stronger adsorption than the planar phase; thus, in comparison to other 2D materials (silicene and germanene) and planar borophene, buckled borophene is a highly suitable candidate as a sensor for actinide complexes

Analytic gradients for state-averaged multiconfiguration pair-density functional theory

Analytic gradients are important for efficient calculations of stationary points on potential energy surfaces, for interpreting spectroscopic observations, and for efficient direct dynamics simulations. For excited electronic states, as are involved in UV–Vis spectroscopy and photochemistry, analytic gradients are readily available and often affordable for calculations using a state-averaged complete active space self-consistent-field (SA-CASSCF) wave function. However, in most cases, a post-SA-CASSCF step is necessary for quantitative accuracy, and such calculations are often too expensive if carried out by perturbation theory or configuration interaction. In this work, we present the analytic gradients for multiconfiguration pair-density functional theory based on SA-CASSCF wave functions, which is a more affordable alternative. A test set of molecules has been studied with this method, and the stationary geometries and energetics are compared to values in the literature as obtained by other methods. Excited-state geometries computed with state-averaged pair-density functional theory have similar accuracy to those from complete active space perturbation theory at the second-order

The OpenMolcas Web: A Community-Driven Approach to Advancing Computational Chemistry

The developments of the open-source OpenMolcas chemistry software environment since spring 2020 are described, with a focus on novel functionalities accessible in the stable branch of the package or via interfaces with other packages. These developments span a wide range of topics in computational chemistry and are presented in thematic sections: electronic structure theory, electronic spectroscopy simulations, analytic gradients and molecular structure optimizations, ab initio molecular dynamics, and other new features. This report offers an overview of the chemical phenomena and processes OpenMolcas can address, while showing that OpenMolcas is an attractive platform for state-of-the-art atomistic computer simulations

Starting grassroots initiatives to foster equity, diversity, and inclusivity in the Chemistry Department at the University of Alberta

Abstract: The University of Alberta Working for Inclusivity in Chemistry (UAWIC) group was formed in 2017 to increase equity, diversity, and inclusion in the Department of Chemistry. With the goals of fostering a community amongst department members and retaining a diverse graduate student population, UAWIC has created initiatives addressing equity, diversity and inclusivity, professional development, and promoted visibility of diversity within the department. Training students how to overcome systemic barriers and providing platforms to share experiences will help aspiring chemists prepare for future career paths and develop a network of mentors and colleagues

Multireference Methods for Calculating the Dissociation Enthalpy of Tetrahedral P4 to Two P2

The potential energy surface for the thermal decomposition of P4 → 2P2 was computed along the C2v reaction trajectory. Single-reference methods were not suitable for describing this complex bond-breaking process, so two multiconfigurational methods, namely, multistate complete active space second-order perturbation theory (MS-CASPT2) and multiconfiguration pair-density functional theory (MC-PDFT), were used with the aim of determining the accuracy and efficiency of these methods for this process. Several active spaces and basis sets were explored. It was found that the multiconfiguration pair-density functional theory method was up to 900 times faster than multistate complete active space second-order perturbation theory while providing similar accuracy

Mechanochemical synthesis of 0D and 3D cesium lead mixed halide perovskites

A simplified mechanochemical synthesis approach for Cs-containing mixed halide perovskite materials of lower and higher dimensionality (0D and 3D, respectively) is presented with stoichiometric control from their halide salts, CsX and PbX2 (X = Cl, Br, I). Excellent optical bandgap tunability through halide substitution is supported by property measurements and changes to the materials' structure. Complementary NMR and XRD methods, along with support from DFT calculations, reveal highly crystalline 0D and 3D solid solutions with a complex arrangement of [PbX6−xXx′]4− pseudooctahedra caused by halide distribution about the Pb centre.<br/

Theoretical Investigation of Single-Molecule-Magnet Behavior in Mononuclear Dysprosium and Californium Complexes

Early-actinide-based (U, Np, and Pu) single-molecule magnets (SMMs) have yet to show magnetic properties similar to those of highly anisotropic lanthanide-based ones. However, there are not many studies exploring the late-actinides (more than half-filled f shells) as potential candidates for SMM applications. We computationally explored the electronic structure and magnetic properties of a hypothetical Cf(III) complex isostructural to the experimentally synthesized Dy(dbm)3(bpy) complex (bpy = 2,2′-bipyridine; dbm = dibenzoylmethanoate) via multireference methods and compared them to those of the Dy(III) analogue. This study shows that the Cf(III) complex can behave as a SMM and has a greater magnetic susceptibility compared to other experimentally and computationally studied early-actinide-based (U, Np, and Pu) magnetic complexes. However, Cf spontaneously undergoes α-decay and converts to Cm. Thus, we also explored the isostructural Cm(III)-based complex. The computed magnetic susceptibility and g-tensor values show that the Cm(III) complex has poor SMM behavior in comparison to both the Dy(III) and Cf(III) complexes, suggesting that the performance of Cf(III)-based magnets may be affected by α-decay and can explain the poor performance of experimentally studied Cf(III)-based molecular magnets in the literature. Further, this study suggests that the ligand field is dominant in Cf(III), which helps to increase the magnetization blocking barrier by nearly 3 times that of its 4f congener

Alkali Tin Halides: Exploring the Local Structure of A2SnX6 (A = K, Rb; X = Cl, Br, I) Compounds Using Solid-State NMR and DFT Computations

Metal-halide perovskites have both interesting structural characteristics and strong potential for applications in devices such as solar cells and light-emitting diodes. While not true perovskites, A 2SnX 6 materials are relatives of traditional ABX 3 perovskites that commonly adopt the K 2PtCl 6 structure type. Herein, we use solid-state nuclear magnetic resonance (NMR) spectroscopy to explore the influence of group 1 (alkali metal) and group 17 (halogen) substitutions on octahedral tilting and spin-orbit (SO) coupling in A 2SnX 6 (A = K +, Rb +; X = Cl -, Br -, or I -) materials. For the monoclinic K 2SnBr 6 and tetragonal Rb 2SnI 6 compounds, the impact of static octahedral tilting on A-site environments is evident in the form of chemical shift anisotropy (CSA) and sizeable quadrupole coupling constants (C Qs) for 39K and 87Rb. Ultrahigh-field NMR analysis combined with periodic density functional theory (DFT) calculations enables successful determination of the relative orientation between the electric field gradient (EFG) and CSA tensors for 39K in K 2SnBr 6. The B-site polyhedral environments are probed throughout the compositional range via 119Sn NMR spectroscopy, demonstrating that the 119Sn chemical shift follows a normal halogen dependence (NHD). Quantum chemical modeling using scalar relativistic and SO DFT on cluster models shows that the NHD is driven by the SO term of the magnetic shielding. Consistent with SO heavy atom effects on NMR chemical shifts, the NHD can be explained in terms of the frontier molecular orbitals and the involvement of Sn and X atomic orbitals in Sn-X bonds. The importance of proper relativistic treatment of heavy atoms is also highlighted by comparing calculations of 119Sn chemical shifts at different levels of theory.</p