Graphdiyne as a high-capacity lithium ion battery anode material

Using the first-principles calculations, we explored the feasibility of using graphdiyne, a 2D layer of sp and sp2 hybrid carbon networks, as lithium ion battery anodes. We found that the composite of the Li-intercalated multilayer ??-graphdiyne was C6Li7.31 and that the calculated voltage was suitable for the anode. The practical specific/volumetric capacities can reach up to 2719 mAh g-1/2032 mAh cm-3, much greater than the values of ???372 mAh g-1/???818 mAh cm -3, ???1117 mAh g-1/???1589 mAh cm-3, and ???744 mAh g-1 for graphite, graphynes, and ??-graphdiyne, respectively. Our calculations suggest that multilayer ??-graphdiyne can serve as a promising high-capacity lithium ion battery anode.open3

BlackVIP: Black-Box Visual Prompting for Robust Transfer Learning

With the surge of large-scale pre-trained models (PTMs), fine-tuning these models to numerous downstream tasks becomes a crucial problem. Consequently, parameter efficient transfer learning (PETL) of large models has grasped huge attention. While recent PETL methods showcase impressive performance, they rely on optimistic assumptions: 1) the entire parameter set of a PTM is available, and 2) a sufficiently large memory capacity for the fine-tuning is equipped. However, in most real-world applications, PTMs are served as a black-box API or proprietary software without explicit parameter accessibility. Besides, it is hard to meet a large memory requirement for modern PTMs. In this work, we propose black-box visual prompting (BlackVIP), which efficiently adapts the PTMs without knowledge about model architectures and parameters. BlackVIP has two components; 1) Coordinator and 2) simultaneous perturbation stochastic approximation with gradient correction (SPSA-GC). The Coordinator designs input-dependent image-shaped visual prompts, which improves few-shot adaptation and robustness on distribution/location shift. SPSA-GC efficiently estimates the gradient of a target model to update Coordinator. Extensive experiments on 16 datasets demonstrate that BlackVIP enables robust adaptation to diverse domains without accessing PTMs' parameters, with minimal memory requirements. Code: \url{https://github.com/changdaeoh/BlackVIP}Comment: Accepted to CVPR 202

Evaluation of Penalized and Nonpenalized Methods for Disease Prediction with Large-Scale Genetic Data

Owing to recent improvement of genotyping technology, large-scale genetic data can be utilized to identify disease susceptibility loci and this successful finding has substantially improved our understanding of complex diseases. However, in spite of these successes, most of the genetic effects for many complex diseases were found to be very small, which have been a big hurdle to build disease prediction model. Recently, many statistical methods based on penalized regressions have been proposed to tackle the so-called "large P and small N" problem. Penalized regressions including least absolute selection and shrinkage operator (LASSO) and ridge regression limit the space of parameters, and this constraint enables the estimation of effects for very large number of SNPs. Various extensions have been suggested, and, in this report, we compare their accuracy by applying them to several complex diseases. Our results show that penalized regressions are usually robust and provide better accuracy than the existing methods for at least diseases under consideration

NiFeOx decorated Ge-hematite/perovskite for an efficient water splitting system

To boost the photoelectrochemical water oxidation performance of hematite photoanodes, high temperature annealing has been widely applied to enhance crystallinity, to improve the interface between the hematite-substrate interface, and to introduce tin-dopants from the substrate. However, when using additional dopants, the interaction between the unintentional tin and intentional dopant is poorly understood. Here, using germanium, we investigate how tin diffusion affects overall photoelectrochemical performance in germanium:tin co-doped systems. After revealing that germanium is a better dopant than tin, we develop a facile germanium-doping method which suppresses tin diffusion from the fluorine doped tin oxide substrate, significantly improving hematite performance. The NiFeOx@Ge-PH photoanode shows a photocurrent density of 4.6mAcm(-2) at 1.23 V-RHE with a low turn-on voltage. After combining with a perovskite solar cell, our tandem system achieves 4.8% solar-to-hydrogen conversion efficiency (3.9mAcm(-2) in NiFeOx@Ge-PH/perovskite solar water splitting system). Our work provides important insights on a promising diagnostic tool for future co-doping system design. Germanium (Ge) has potential as a dopant suitable for the hematite-based photoelectrochemical water splitting system. Here, the authors report the fabrication of Ge doped porous hematite and demonstrate an efficient tandem system of Ge doped porous hematite and the perovskite solar cell

Stabilization of LiBH4 superionic phase by halide doping and H disordering

We performed first-principles density-functional theory calculations to investigate the structural properties and the effect of halide ion doping to the superionic-conducting, high-temperature phase and the effect of halide doping on the phase of LiBH4. It is computationally demonstrated that the superionic phase is stabilized owing to the halide doping with the large ions which fill the interlayer space of the superionic phase. The H-disordered phase is observed in the structure and is found to contribute to the stabilization of the superionic phase.close0

Visible light photoreactivity from hybridization states between carbon nitride bandgap states and valence states in Nb and Ti oxides

For better efficiency as photocatalysts, N-doping for visible light reactivity has been intensively studied in Lamellar niobic and titanic solid acids (HNb3O8, H2Ti4O9), and its microscopic structures have been debated in this decade. We calculate the layered solid acids' structures and bandgaps. Bandgap reduction by carbon nitride adsorption in interlayer space is observed computationally. It originates from localized nitrogen states which form delocalized top-valence states by hybridizing with the host oxygen states and can contribute to photo-current.close

Emergence of the giant out-of-plane Rashba effect and tunable nanoscale persistent spin helix in ferroelectric SnTe thin films

A non-vanishing electric field inside a non-centrosymmetric crystal transforms into a momentum-dependent magnetic field, namely, a spin???orbit field (SOF). SOFs are of great use in spintronics because they enable spin manipulation via the electric field. At the same time, however, spintronic applications are severely limited by the SOF, as electrons traversing the SOF easily lose their spin information. Here, we propose that in-plane ferroelectricity in (001)-oriented SnTe thin films can support both electrical spin controllability and suppression of spin dephasing. The in-plane ferroelectricity produces a unidirectional out-of-plane Rashba SOF that can host a long-lived helical spin mode known as a persistent spin helix (PSH). Through direct coupling between the inversion asymmetry and the SOF, the ferroelectric switching reverses the out-of-plane Rashba SOF, giving rise to a maximally field-tunable PSH. Furthermore, the giant out-of-plane Rashba SOF seen in the SnTe thin films is linked to the nano-sized PSH, potentially reducing spintronic device sizes to the nanoscale. We combine the two ferroelectric-coupled degrees of freedom, longitudinal charge and transverse PSH, to design intersectional electro-spintronic transistors governed by non-volatile ferroelectric switching within nanoscale lateral and atomic-thick vertical dimensions

Room-temperature ferromagnetism from an array of asymmetric zigzag-edge nanoribbons in a graphene junction

Room-temperature ferromagnetism in graphene layers with defects has been experimentally measured. Despite disagreement around the intrinsic origin of carbon magnetism, experimental evidence has supported the existence of paramagnetism or ferromagnetism in carbon materials. Convincing theoretical explanations, however, have not yet been proposed. In this work, density functional theory calculations were used to suggest a plausible explanation for this phenomenon as it is observed at the zigzag grain boundaries of a mismatched single-double-single-layer graphene junction. We identified asymmetric zigzag-edge graphene nanoribbons that display ferromagnetic properties in a graphene junction structure. Two ferromagnetic asymmetric zigzag graphene nanoribbons displayed antiferromagnetic coupling in a defect-free structure at the grain boundary. The introduction of a vacancy or N-substitutional defect was found to destroy the magnetism on one side only; the nanoribbon on the other side continued to display a large ferromagnetic exchange coupling. The ferromagnetic nanoribbon in the junction was ferromagnetically correlated with other nanoribbons in the two-dimensional junction array, yielding a Curie temperature well-above room temperature. Moreover, the ferromagnetic correlation was observed regardless of the arrangement of the magnetic layers, enabling ferromagnetic ordering within the graphene junction array

Mechanism of CO Oxidation on Pd/CeO2(100): The Unique Surface-Structure of CeO2(100) and the Role of Peroxide

Understanding the atomic mechanism of low-temperature CO oxidation on a heterogeneous catalyst is challenging. We performed density functional theory (DFT) calculations to identify the surface structure and reaction mechanism responsible for low-temperature CO oxidation on Pd/CeO2(100) surfaces. DFT calculations reveal the formation of a unique zigzag chain structure by the oxygen and Ce atoms of the topmost surface of CeO2(100) with Pd atoms located between the zigzag chains. O(2)adsorbed on such Pd atoms is stable in the presence of CO but plays a very important role in lowering the activation barrier for low-temperature CO oxidation by forming a square-planar PdO(4)structure and facilitating further O(2)adsorption.In-situRaman spectroscopy studies confirm the adsorbed oxygen species to be peroxides. The calculated activation barrier for CO oxidation, based on the mechanism suggested by these unique structures and peroxides, is 31.2 kJ/mol, in excellent agreement with our experimental results