Youhua Luo

Low-Energy Isomer Identification, Structural Evolution, and Magnetic Properties in Manganese-Doped Gold Clusters MnAun (n=1-16)

The size-dependent electronic, structural, and magnetic properties of Mn-doped gold clusters have been systematically investigated by using relativistic all-electron density functional theory with generalized gradient approximation. A number of new isomers are obtained for neutral MnAu(n) (n = 1-16) clusters to probe the structural evolution. The two-dimensional (2D) to three-dimensional (3D) transition occurs in the size range n = 7-10 with manifest structure competitions. From size n = 13 to n = 16, the MnAu(n) prefers a gold cage structure with Mn atom locating at the center. The relative stabilities of the ground-state MnAu(n) clusters show a pronounced odd-even oscillation with the number of Au atoms. The magnetic moments of MnAu(n) clusters vary from 3 μ(B) to 6 μ(B) with the different cluster size, suggesting that nonmagnetic Au(n) clusters can serve as a flexible host to tailor the dopants magnetism, which has potential applications in new nanomaterials with tunable magnetic properties.

Magnetic superatoms in VLi(n) (n = 1-13) clusters: a first-principles prediction.

We demonstrated a first-principles investigation to search for magnetic superatoms in the vanadium-doped lithium clusters VLi(n) (n = 1-13). The stabilities of VLi(n) clusters were determined through geometrical and electronic optimizations. It is found that the growth pattern of VLi(n) in 3-space follows adding a Li atom capped on VLi(n-1) clusters. All doped clusters show larger relative binding energies compared with pure Li(n+1) partners and display tunable magnetic properties. When n = 8-13, the VLi(n) clusters adopt a cage-like structure with an endohedral V atom and are identified as superatoms with their magnetic moments successively decreasing from 5 to 0 μB. The isolated VLi8 superatom is emphasized due to its robust magnetic moment as well as high structural and chemical stability analogue of a single Mn(2+) ion. Molecular orbitals analysis shows that VLi8 has an electronic configuration of 1S(2)1P(6)1D(5), exhibiting Hunds filling rule of maximizing the spin-like atoms. Electronic shell structures of 1S(2) and 1P(6) are virtually unchanged in Li9 cluster as the V atom substitutes for the embedded Li atom, indicating that the electron-shell-closing model is valid for explaining its structures and stabilities. The results show that the tailored magnetic building blocks for nanomaterials can be formed by seeding magnetic dopants into alkali metal cluster cages.

First-principles investigations of chirality in trimetallic alloy clusters: AlMnAun (n = 1-7).

Chirality, also called handedness, plays a crucial role in function ranging from biological self-assembly schemes, organic polymer functionalities, to optical material designs. In this Article, we demonstrated a first-principles investigation of chirality in magnetic AlMnAun(0/+1/-1) (n = 1-7) clusters. Optimized structures of the AlMnAun clusters exhibit configurational combinations between AlAun+1 and MnAun+1 clusters, indicating a subtle but equal competition between Au-Al and Au-Mn interactions in the alloy clusters. High magnetic moments are equal to or greater than 4μB in AlMnAun clusters due to the presence of the Mn dopant. Chirality turns up with the forms of right-handed and left-handed in stable AlMnAu5, AlMnAu6, and AlMnAu7 clusters. As a result, reflection symmetries are found in vibrational Raman and circular dichroism spectra of these chiral pairs. The present study shows that chiral magnetic clusters can be composed by doping two heteroatoms with one intrinsic magnetic dopant into small gold clusters.

Magnetic MoS2 pizzas and sandwiches with Mnn (n=1-4) cluster toppings and fillings: A first-principles investigation

The inorganic layered crystal (ILC) MoS2 in low dimensions is considered as one of the most promising and efficient semiconductors. To enable the magnetism and keep intrinsic crystal structures, we carried out a first-principles study of the magnetic and semiconductive monolayer MoS2 adsorbed with the Mnn (n = 1–4) clusters, and bilayer MoS2 intercalated with the same clusters. Geometric optimizations of the Mnn@MoS2 systems show the complexes prefer to have Mnn@MoS2(M) pizza and Mnn@MoS2(B) sandwich forms in the mono- and bi-layered cases, respectively. Introductions of the clusters will enhance complex stabilities, while bonds and charge transfers are found between external Mn clusters and the S atoms in the hosts. The pizzas have medium magnetic moments of 3, 6, 9, 4 μB and sandwiches of 3, 2, 3, 2 μB following the manganese numbers. The pizzas and sandwiches are semiconductors, but with narrower bandgaps compared to their corresponding pristine hosts. Direct bandgaps were found in the Mnn@MoS2(M) (n = 1,4) pizzas, and excitingly in the Mn1@MoS2(B) sandwich. Combining functional clusters to the layered hosts, the present work shows a novel material manipulation strategy to boost semiconductive ILCs applications in magnetics.

Transition Metal Adsorbed-Doped ZnO Monolayer: 2D Dilute Magnetic Semiconductor, Magnetic Mechanism, and Beyond 2D

As an improvement over organic or inorganic layered crystals, the synthetic monolayer ZnO(M) inherits semiconductivity and hostability from its bulk, yet it acts as a promising host for dilute magnetic semiconductors. Here, we report the electronic and magnetic properties of ZnO(M) doped with one 3d transition metal ion and simultaneously adsorbed with another 3d transition metal ion. Two sequences are studied, one where the dopant is fixed to Mn and the adsorbate is varied from Sc to Zn and another where the dopant and adsorbate are reversed. First-principles results show that the stable adsorbed−doped systems possess a lower bandgap energy than that of the host. System magnetic moments can be tuned to |5 – x|μB, where x refers to the magnetic moment of the individual 3d atom. An interplay between superexchange and direct exchange yields a ferromagnetic system dually adsorbed−doped with Mn. In addition to a novel material design route, the magnetic interaction mechanism is found beyond two dimensions, having been identified for its three-dimensional bulk and zero-dimensional cluster counterparts.

Unraveling Special Structures and Properties of Gold-Covered Gold-Core Cage on Au33-42 Nanoparticles.

New low-energy atomic structures and properties of medium-size gold nanoparticles (Au33-42) are studied, where the atomic positions of gold atoms are obtained on the basis of the generic formulation of shell and core concept. Hollow cage, tube-like, double-layered flat, fcc-like, and close-packed configurations are predicted. Relativistic density functional theory optimization indicated that low-symmetry stuffed configurations are all lower in energy than the others. Further analysis of the optimized structures of Au33-42 nanoparticles shows that these gold cores are all four-atom tetrahedral structures and similar to each other; only the number and positions of gold atoms at the surface of gold core are different. Compared with structure and electronic properties, Au33-42 nanoparticles have different structure stabilities and chemical activities. But they are all hybridizations of sp and d electrons. The obtained information forms the basis for future chemisorption studies to unravel the catalytic effects of gold nanoparticles.

Structural, electronic, and magnetic properties in FeAlAun (n=1-6) clusters: A first-principles study

The geometries, electronic and magnetic properties of the trimetallic clusters FeAlAun (n = 1-6) are systematically investigated using density functional theory (DFT). A number of new isomers are obtained to probe the structural evolutions. All doped clusters show larger relative binding energies than pure Aun+2 partners, indicating that doping with Fe and Al atoms can stabilize the Au-n clusters. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps, vertical ionization potentials and vertical electron affinities are also studied and compared with those of pure gold clusters. Magnetism calculations demonstrate that the magnetic moments of FeAlAun clusters each show a pronounced odd-even oscillation with the number of Au atoms.

Evolution of lithium clusters to superatomic Li3O

Accurate knowledge of the oxidation stages of lithium is crucially important for developing next-generation Li-air batteries. The intermediate oxidation stages, however, differ in the bulk and cluster forms of lithium. In this letter, using first-principles calculations, we predict several reaction pathways leading to the formation of Li3O+ superatoms. Experimental results based on time-of-flight mass spectrometry and laser ablation of oxidized lithium bulk samples agreed well with our theoretical calculations. Additionally, the highest occupied molecular orbital-lowest unoccupied molecular orbital gap of Li3O+ was close to the energy released in one of these reaction paths, indicating that the superatom could act as a candidate charge-discharge unit.