Energetic and Kinetic Competition on the Stability of Pd Clusters: Ab Initio Molecular Dynamics Simulations.

Material stability is the focus on both experiments and calculations, which includes the energetic stability at the static state and the thermodynamic stability at the kinetic state. To show whether energetics or kinetics dominates on material stability, this study focuses on the Pd clusters, because of their observable magnetic moment in experiment. Energetically, the CALYPSO searching method and first-principles calculations find that Pd(C) is the ground state at 0 K while the static frequency calculations demonstrate that the icosahedron Pd(I) becomes more favorable on free energy as temperature increases.

Spin-polarized p-block antimony/bismuth single-atom catalysts on defect-free rutile TiO(110) substrate for highly efficient CO oxidation.

Developing high-loading spin-polarized p-block-element-based single-atom catalysts (p-SACs) upon defect-free substrates for various chemical reactions wherein spin selection matters is generally considered a formidable challenge because of the difficulty of creating high densities of underpinning stable defects and the delocalized electronic features of p-block elements. Here our first-principles calculations establish that the defect-free rutile TiO(110) wide-bandgap semiconducting anchoring support can stabilize and localize the wavefunctions of p-block metal elements (Sb and Bi) strong ionic bonding, forming spin-polarized -SACs. Cooperated by the underlying d-block Ti atoms a delicate spin donation-back-donation mechanism, the p-block single-atom reactive center Sb(Bi) exhibits excellent catalysis for spin-triplet O activation and CO oxidation in alignment with Wigner's spin selection rule, with a low rate-limiting reaction barrier of ∼0.

Centimeter-sized diamond composites with high electrical conductivity and hardness.

Achieving high-performance materials with superior mechanical properties and electrical conductivity, especially in large-sized bulk forms, has always been the goal. However, it remains a grand challenge due to the inherent trade-off between these properties. Herein, by employing nanodiamonds as precursors, centimeter-sized diamond/graphene composites were synthesized under moderate pressure and temperature conditions (12 GPa and 1,300 to 1,500 °C), and the composites consisted of ultrafine diamond grains and few-layer graphene domains interconnected through covalently bonded interfaces.

Synergetic Role of Thermal Catalysis and Photocatalysis in CO Reduction on Cu/MoS.

Effective activation of CO is a primarily challenging issue in CO reduction to value-added hydrocarbon chemicals, due to the large energy gap between the highest-occupied and lowest-unoccupied molecular orbitals (HOMO-LUMO). Here, we employ state-of-the-art first-principles calculations to explore the synergetic role of thermal catalysis and photocatalysis in CO reduction, on typical single-atom scale catalyst, i.e.

Synergetic Catalysis of Magnetic Single-Atom Catalysts Confined in Graphitic-CN/CeO(111) Heterojunction for CO Oxidization.

Magnetic single-atom catalysts (MSAC), due to the intrinsic spin degree of freedom, are of particular importance relative to other conventional SAC for applications in various catalytic processes, especially in those cases that involve spin-triplet O. However, the bottleneck issue in this field is the clustering of the SAC during the processes. Here using first-principles calculations we predict that Mn atoms can be readily confined in the interface of the porous g-CN/CeO(111) heterostructure, forming high-performance MSAC for O activation via a delicate synergetic mechanism of charge transfer, mainly provided by the p-block g-CN overlayer mediated by the d-block Mn active site, and spin selection, preserved mainly through active participation of the f-block Ce atoms and/or g-CN, which effectively promotes the CO oxidization.

Synergetic Charge Transfer and Spin Selection in CO Oxidation at Neighboring Magnetic Single-Atom Catalyst Sites.

Deciphering the precise physical mechanism of interaction between an adsorbed species and a reactive site in heterogeneous catalysis is crucial for predictive design of highly efficient catalysts. Here, using first-principles calculations we identify that the two-dimensional ferromagnetic metal organic framework of MnCH can serve as a highly efficient single-atom catalyst for spin-triplet O activation and CO oxidation. The underlying mechanism is via "concerted charge-spin catalysis", involving a delicate synergetic process of charge transfer, provided by the hosting Mn atom, and spin selection, preserved through active participation of its nearest neighboring Mn atoms for the crucial step of O activation.

Negative Differential Friction Predicted in 2D Ferroelectric In Se Commensurate Contacts.

At the macroscopic scale, the friction force (f) is found to increase with the normal load (N), according to the classic law of Da Vinci-Amontons, namely, f = µN, with a positive definite friction coefficient (μ). Here, first-principles calculations are employed to predict that, the static force f, measured by the corrugation in the sliding potential energy barrier, is lowered upon increasing the normal load applied on one layer of the recently discovered ferroelectric In Se over another commensurate layer of In Se . That is, a negative differential friction coefficient μ can be realized, which thus simultaneously breaking the classic Da Vinci-Amontons law.

Highly efficient catalytic properties of Sc and Fe single atoms stabilized on a honeycomb borophene/Al(111) heterostructure via a dual charge transfer effect.

Theoretical design and experimental fabrication of highly efficient single-atom catalysts (SACs) containing isolated metal atoms monodispersed on appropriate substrates have surged to the forefront of heterogeneous catalysis in recent years. Nevertheless, the instability of SACs, i.e.

Strain induced spin-splitting and half-metallicity in antiferromagnetic bilayer silicene under bending.

Searching for half-metals in low dimensional materials is not only of scientific importance, but also has important implications for the realization of spintronic devices on a small scale. In this work, we show theoretically that simple bending can induce spin-splitting in bilayer silicene. For bilayer silicene with Bernal stacking, the monolayer has a long range ferromagnetic spin order and between the two monolayers, the spin orders are opposite, giving rise to an antiferromagnetic configuration for the ground state of the bilayer silicene.

Thermal Stability of Ag Clusters Studied by Ab Initio Molecular Dynamics Simulations.

Identification of the geometric structures of silver clusters is of great importance in future nanotechnologies due to their superior properties. Nevertheless, some ground-state structures are still in academic debate, partly because the experiments and theoretical calculations are not performed at the same temperatures. For example, silver clusters usually have compact configurations.

Unconventional deformation potential and half-metallicity in zigzag nanoribbons of 2D-Xenes.

Realization of half-metallicity (HM) in low dimensional materials is a fundamental challenge for nano spintronics and a critical component for developing alternative generations of information technology. Using first-principles calculations, we reveal an unconventional deformation potential for zigzag nanoribbons (NRs) of 2D-Xenes. Both the conduction band minimum (CBM) and valence band maximum (VBM) of the edge states have negative deformation potentials.

Formation of Bloch Flat Bands in Polar Twisted Bilayers without Magic Angles.

The existence of Bloch flat bands of electrons provides a facile pathway to obtain exotic quantum phases owing to strong correlation. Despite the established magic angle mechanism for twisted bilayer graphene, understanding of the emergence of flat bands in twisted bilayers of two-dimensional polar crystals remains elusive. Here, we show that due to the polarity between constituent elements in the monolayer, the formation of complete flat bands in twisted bilayers is triggered as long as the twist angle is less than a certain critical value.

Strain Engineering of a Defect-Free, Single-Layer MoS Substrate for Highly Efficient Single-Atom Catalysis of CO Oxidation.

Single-atom catalysts (SACs) are of great scientific and technical importance due to their low cost, high site density, and high specificity to enhance chemical reactions. Nevertheless, a major issue that severely limits the practical exploration of SACs is their instability, i.e.

Twist-driven separation of -type and -type dopants in single-crystalline nanowires.

The distribution of dopants significantly influences the properties of semiconductors, yet effective modulation and separation of -type and -type dopants in homogeneous materials remain challenging, especially for nanostructures. Employing a bond orbital model with supportive atomistic simulations, we show that axial twisting can substantially modulate the radial distribution of dopants in Si nanowires (NWs) such that dopants of smaller sizes than the host atom prefer atomic sites near the NW core, while dopants of larger sizes are prone to staying adjacent to the NW surface. We attribute such distinct behaviors to the twist-induced inhomogeneous shear strain in NW.

Interplay between the spin-selection rule and frontier orbital theory in O2 activation and CO oxidation by single-atom-sized catalysts on TiO2(110).

Exploration of the catalytic activity of low-dimensional transition metal (TM) or noble metal catalysts is a vital subject of modern materials science because of their instrumental role in numerous industrial applications. Recent experimental advances have demonstrated the utilization of single atoms on different substrates as effective catalysts, which exhibit amazing catalytic properties such as more efficient catalytic performance and higher selectivity in chemical reactions as compared to their nanostructured counterparts; however, the underlying microscopic mechanisms operative in these single atom catalysts still remain elusive. Based on first-principles calculations, herein, we present a comparative study of the key kinetic rate processes involved in CO oxidation using a monomer or dimer of two representative TMs (Pd and Ni) on defective TiO2(110) substrates (TMn@TiO2(110), n = 1, 2) to elucidate the underlying mechanism of single-atom catalysis.

Sub-surface alloying largely influences graphene nucleation and growth over transition metal substrates.

Sub-surface alloying (SSA) can be an effective approach to tuning surface functionalities. Focusing on Rh(111) as a typical substrate for graphene nucleation, we show strong modulation by SSA atoms of both the energetics and kinetics of graphene nucleation simulated by first-principles calculations. Counter-intuitively, when the sub-surface atoms are replaced by more active solute metal elements to the left of Rh in the periodic table, such as the early transition metals (TMs), Ru and Tc, the binding between a C atom and the substrate is weakened and two C atoms favor dimerization.