Density functional theory calculations and crystal structure predictions using the particle swarm optimization method have been combined to determine stable hydrides of lead under pressure. In contrast to other group-IVa hydrides, the stoichiometry PbH6 is the first hydride to become stable, at just under 1 Mbar. For two previously studied stoichiometries PbH4 and PbH8, new energetically favorable phases were identified to become stable around 2 Mbar. In all structures, the hydrogenic sublattices comprises negatively charged H δ− 2 molecules. Competitive PbH4 and PbH6 structures are layered. PbH6 features H2 molecules intercalated between hexagonal close packed Pb-layers, the stable phase of dense pure lead, thus offering a potentially straightforward route towards synthesis. In PbH8, the Pb lattice adapts a beta-Sn structure and hydrogen atoms form quasi-1D-chains. All structures were found to be metallic and to feature superconductivity in their respective stability range, with moderately high Tc in the range 60-100 K for PbH4 and PbH6, and 161-178 K for PbH8.

Binary boron-based compounds are expected to possess unique molecular architecture and chemical bonding. Here, we explore how incorporation of a valence isoelectronic Al atom into boron clusters containing from 10 to 20 atoms modifies the structures and properties of the initial clusters. The global minima structures of neutral and anionic Al-doped boron cluster in the size range from 10 to 20 have been identified using the Crystal structure AnaLYsis by Particle Swarm Optimization method. The states with the promising geometrical structures are reoptimized using density functional theory and tripleζ basis sets. It is found that the geometries of the ground states of the AlB n and AlB n − clusters possess planar, quasi-planar, and exohedral topologies. A nearly circular planar AlB 18 − cluster with C 2v symmetry and a large energy gap 2.98 eV has been discovered. The calculated photoelectron spectra of the anions are well in accord with the experimental spectra. The chemical-bonding analysis suggests that both large HLG and double π-aromaticity have much contribution to the electronic stability of AlB 18 − cluster. Our results elucidate the structural growth behavior of Al-doped boron clusters and enrich the growth pattern and chemical bonding nature of boron-based clusters.

The global-minimum structures of RuBn0/− (n = 9–20) clusters have been determined by the CALYPSO method combined with DFT calculations.

Beryllium-doped boron clusters display essential similarities to borophene (boron sheet) with a molecular structure characterized by remarkable properties, such as anisotropy, metallicity and high conductivity. Here we have determined low-energy structures of BeBn0/− (n = 10–20) clusters by utilizing CALYPSO searching program and DFT optimization. The results indicated that most ground states of clusters prefer plane or quasi-plane structures by doped Be atom. A novel unexpected fascinating planar BeB16− cluster with C2v symmetry is uncovered which possesses robust relative stability. Furthermore, planar BeB16− offers a possibility to construct metallo-borophene nano-materials. Molecular orbital and chemical bonding analysis reveal the peculiarities of BeB16− cluster brings forth the aromaticity and the strong interaction of B-B σ-bonds in boron network.

Doping of boron-based materials with transition metal atoms allows one to tune or modify the properties and structure of the materials. In this work, an extensive search for the global minima on potential energy surfaces of ScBn and ScB clusters has been performed using the CALYPSO method. The structural evolution of scandium doped boron clusters of this range is found to proceed in three steps; namely, the formation of half-sandwich type structures is followed by the formation of drum-like structures with the Sc atom located at the center and terminates with the cage-like structures. It is also found that highly symmetrical geometric structures are more common for the smaller size range of . The neutral ScB13 cluster is identified as magic on the basis of an analysis of relative stabilities in the ScBn series. Our analysis of chemical bonding has shown that the stability of this cluster is mainly due to the formation of several delocalized -bonding molecular orbitals composed of Sc 3d and B 2s atomic orbitals. These bonds appear to be responsible for the enhanced stability of ScB13 with respect to other Sc-doped boron clusters.

The coalescence of two Fe8N as well as the structure of the Fe16N2 cluster was studied using density functional theory with the generalized gradient approximation and a basis set of triple-zeta quality.

After reports of unusually low oxidation states of lanthanide elements in Ln−B clusters and their inverse sandwich geometrical topologies, the interest shifted from boride clusters doped with transition metal (TM) elements to the boride clusters doped with lanthanide atoms. In this work, the results obtained by a combined approach consisting of CALYPSO structure predictions and density functional theory (DFT) calculations for the neutral and anionic PrB n series, n = 7−16, are reported. A close agreement between our calculated vertical detachment energies and experimental data supports the accuracy of the results obtained. Contrary to the medium-size TM-doped medium boron clusters, which prefer three types of structural configurations, all lowest-energy states of the medium-size Pr-doped boron clusters have half-sandwich geometries. An interesting structural evolution pattern was found for both neutral and anionic PrB n clusters at n = 7, 10, 13, and 16, which includes quasi-planar B 7 units half-sandwiching the Pr atom. Unusual oxidation numbers of +2 and +1 were found for the Pr atom in the PrB 7 − and PrB 8 − anions, respectively. Chemical bonding analysis for the neutral PrB 7 and PrB 13 clusters revealed that their high stability stems from interactions between Pr 5d and B 2p orbitals. A stable tubular-shaped PrB 30 cluster is proposed as a promising building block for boron-based nanotubes.

Transition metal-doped electronic deficiency boron clusters have led to a vast variety of electronic bonding properties in chemistry and materials science. We have determined the ground state structures of PdB n 0/– (n = 10–20) clusters by performing CALYPSO search and density functional theory (DFT) optimization. The identified lowest energy structures for both neutral and anionic Pd-doped boron clusters follow the structure evolution from two dimensional (2D) planar configurations to 3D distorted Pd-centered drum-like or tubular structures. Photoelectron spectra are simulated by time-dependent DFT theoretical calculations, which is a powerful method to validate our obtained ground-state structures. More interestingly, two “magic” number clusters, PdB12 and PdB16, are found with enhanced stability in the middle size regime studied. Subsequently, molecular orbital and adaptive natural density partitioning analyses reveal that the high stability of the PdB16 cluster originates from doubly σ π aromatic and bonding interactions of d-type atomic orbitals of the Pd atom with tubular B16 units. The tubular C 8v PdB16 cluster, with robust relative stability, is an ideal embryo for forming finite and infinite nanotube nanomaterials.