Data-Efficient Multifidelity Training for High-Fidelity Machine Learning Interatomic Potentials.

Machine learning interatomic potentials (MLIPs) are used to estimate potential energy surfaces (PES) from calculations, providing near-quantum-level accuracy with reduced computational costs. However, the high cost of assembling high-fidelity databases hampers the application of MLIPs to systems that require high chemical accuracy. Utilizing an equivariant graph neural network, we present an MLIP framework that trains on multifidelity databases simultaneously.

Nitrogen Complex-Driven Vacancy Cluster in Group-III Nitrides.

A series of experiments have elucidated the primary defects in group-III nitride epilayers, identifying vacancy clusters due to cation migration at interfaces to mitigate strained lattice. While the occurrence of these defects is well-documented, the underlying electronic mechanisms driving vacancy agglomeration in nitrides and their alloys remain poorly understood. In this study, we uncovered a previously unreported ground state of two metal vacancies driven by the migration of kinetically unstable nitrogen atoms using an approach.

Ultrahigh Sensitivity for Thermographic Human-Machine Interface via Precious Metals Atomic Layer Deposition on V-MXene: Computational and Experimental Exploration.

Global healthcare based on the Internet of Things system is rapidly transforming to measure precise physiological body parameters without visiting hospitals at remote patients and associated symptoms monitoring. 2D materials and the prevailing mood of current ever-expanding MXene-based sensing devices motivate to introduce first the novel iridium (Ir) precious metal incorporated vanadium (V)-MXene via industrially favored emerging atomic layer deposition (ALD) techniques. The current work contributes a precise control and delicate balance of Ir single atomic forms or clusters on the V-MXene to constitute a unique precious metal-MXene embedded heterostructure (Ir-ALD@V-MXene) in practical real-time sensing healthcare applications to thermography with human-machine interface for the first time.

Why Te Doping Can Break the Traditional n-Type Doping Limit of Silicon.

We report a theoretical investigation of the impact of hyperdoping with chalcogens (Se and Te) and pnictogens (P and As) on free-carrier concentrations of Si, employing density functional theory calculations. Our results illustrate that isolated substitutional chalcogens in moderately doped Si function as deep donors that are difficult to ionize at room temperature, unlike isolated substitutional pnictogens. The pairing of substitutional defects is found to be energetically favorable for every dopant element, implying that the concentration of substitutional pairs can be significant in hyperdoped Si.

Enhanced thermal stability by short-range ordered ferroelectricity in KNaNbO-based piezoelectric oxides.

Industrial application of lead-free piezoelectric ceramics is prevented by intrinsic thermal instability. Herein, we propose a method to achieve outstanding thermal stability of converse piezoelectric constant () in lead-free potassium sodium niobate (KNN)-based ceramics by inducing a synergistic interaction between the grain size and polar configuration. Based on computational methods using phase-field simulations and first-principles calculations, the relationship between the grain size and polar configuration is demonstrated, and the possibility of achieving improved thermal stability in fine grains is suggested.

Native point defects in antiperovskite BaSbN: a promising semiconductor for photovoltaics.

We present a theoretical investigation on intrinsic defects of hexagonal antiperovskite BaSbN, a promising lead-free semiconductor for photovoltaics. Our hybrid functional calculations reveal that Ba, Sb and N vacancies, and N interstitials become major point defects in BaSbN. Conversely, other interstitials and antisites have large formation energies and their concentrations are controllable.

Hydrogen-Doping-Enabled Boosting of the Carrier Mobility and Stability in Amorphous IGZTO Transistors.

This study investigated the effect of hydrogen (H) on the performance of amorphous In-Ga-Zn-Sn oxide (-InGaZnSnO) thin-film transistors (TFTs). Ample H in plasma-enhanced atomic layer deposition (PEALD)-derived SiO can diffuse into the underlying -IGZTO film during the postdeposition annealing (PDA) process, which affects the electrical properties of the resulting TFTs due to its donor behavior in the -IGZTO. The -InGaZnSnO TFTs at the PDA temperature of 400 °C exhibited a remarkably higher field-effect mobility (μ) of 85.

CRTC3, a sensor and key regulator for melanogenesis, as a tunable therapeutic target for pigmentary disorders.

Although CREB phosphorylation is known to be essential in UVB/cAMP-stimulated melanogenesis, CREB null mice did not show identifiable pigmentation phenotypes. Here, we show that CREB-regulated transcription co-activator 3 (CRTC3) quantitatively regulates and orchestrates melanogenesis by directly targeting microphthalmia-associated transcription factor (MITF) and regulating the expression of most key melanogenesis-related genes. We analyzed CRTC3-null, KRT14-SCF transgenic, and their crossover mice.

Reversible Manipulation of Photoconductivity Caused by Surface Oxygen Vacancies in Perovskite Stannates with Ultraviolet Light.

Programmable optoelectronic devices call for the reversible control of the photocarrier recombination process by in-gap states in oxide semiconductors. However, previous approaches to produce oxygen vacancies as a source of in-gap states in oxide semiconductors have hampered the reversible formation of oxygen vacancies and their related phenomena. Here, a new strategy to manipulate the 2D photoconductivity from perovskite stannates is demonstrated by exploiting spatially selective photochemical reaction under ultraviolet illumination at room temperature.

First-Principles Calculations of Luminescence Spectra of Real-Scale Quantum Dots.

The luminescence line shape is an important feature of semiconductor quantum dots (QDs) and affects performance in various optical applications. Here, we report a first-principles method to predict the luminescence spectrum of thousands of atom QDs. In our approach, neural network potential calculations are combined with density functional theory calculations to describe exciton-phonon coupling (EPC).

Identification of Active Sites for CO Reduction on Graphene-Supported Single-Atom Catalysts.

Transition metal- and nitrogen-codoped graphene (referred to as M-N-G, where M is a transition metal) has emerged as an important type of single-atom catalysts with high selectivities and activities for electrochemical CO reduction (CO R) to CO. However, despite extensive previous studies on the catalytic origin, the active site in M-N-G catalysts remains puzzling. In this study, density functional theory calculations and computational hydrogen electrode model is used to investigate CO R reaction energies on Zn-N-G, which exhibits outstanding catalytic performance, and to examine kinetic barriers of reduction reactions by using the climbing image nudged elastic band method.

A band-gap database for semiconducting inorganic materials calculated with hybrid functional.

Semiconducting inorganic materials with band gaps ranging between 0 and 5 eV constitute major components in electronic, optoelectronic and photovoltaic devices. Since the band gap is a primary material property that affects the device performance, large band-gap databases are useful in selecting optimal materials in each application. While there exist several band-gap databases that are theoretically compiled by density-functional-theory calculations, they suffer from computational limitations such as band-gap underestimation and metastable magnetism.

Antiperovskite Oxides as Promising Candidates for High-Performance Ferroelectric Photovoltaics: First-Principles Investigation on BaAsO and BaSbO.

Owing to polarization-driven efficient charge carrier separation, ferroelectric semiconductors with narrow band gaps (∼1.3 eV) can constitute an ideal active layer for photovoltaics (PVs), as demonstrated in recent studies on lead halide perovskite solar cells. In this study, antiperovskite oxides with a composition of BaPnO (Pn = As or Sb) are proposed as promising candidates for high-performance ferroelectric PVs.

Fundamental Limit of the Emission Linewidths of Quantum Dots: An Ab Initio Study of CdSe Nanocrystals.

The emission linewidth of a semiconducting nanocrystal (NC) significantly affects its performance in light-emitting applications, but its fundamental limit is still elusive. Herein, we analyze the exciton-phonon coupling (EPC) from Huang-Rhys (HR) factors using ab initio calculations and compute emission line shapes of CdSe NCs. When surface traps are absent, acoustic modes are found to dominate EPC.

Enhancement of Photoluminescence Quantum Yield and Stability in CsPbBr Perovskite Quantum Dots by Trivalent Doping.

We determine the influence of substitutional defects on perovskite quantum dots through experimental and theoretical investigations. Substitutional defects were introduced by trivalent dopants (In, Sb, and Bi) in CsPbBr by ligand-assisted reprecipitation. We show that the photoluminescence (PL) emission peak shifts toward shorter wavelengths when doping concentrations are increased.

Effects of the Heterointerface on the Growth Characteristics of a Brownmillerite SrFeO Thin Film Grown on SrRuO and SrTiO Perovskites.

Manipulation of the heterointerfacial structure and/or chemistry of transition metal oxides is of great interest for the development of novel properties. However, few studies have focused on heterointerfacial effects on the growth characteristics of oxide thin films, although such interfacial engineering is crucial to determine the growth dynamics and physical properties of oxide heterostructures. Herein, we show that heterointerfacial effects play key roles in determining the growth process of oxide thin films by overcoming the simple epitaxial strain energy.

Suppression of Brown Adipocyte Autophagy Improves Energy Metabolism by Regulating Mitochondrial Turnover.

The high abundance of mitochondria and the expression of mitochondrial uncoupling protein 1 (UCP1) confer upon brown adipose tissue (BAT) the unique capacity to convert chemical energy into heat at the expense of ATP synthesis. It was long believed that BAT is present only in infants, and so, it was not considered as a potential therapeutic target for metabolic syndrome; however, the discovery of metabolically active BAT in adult humans has re-stimulated interest in the contributions of BAT metabolic regulation and dysfunction to health and disease. Here we demonstrate that brown adipocyte autophagy plays a critical role in the regulation BAT activity and systemic energy metabolism.

Unveiling Electrochemical Reaction Pathways of CO Reduction to C Species at S-Vacancies of MoS.

Although C species such as CO and CH constitute the majority of CO reduction (CO  R) products on known catalysts, recent experiments showed that 1-propanol with two C-C bonds is produced as the main CO  R product on MoS single crystals in aqueous electrolytes. Herein, the CO  R mechanism on MoS is investigated by using first-principle calculations. Focusing on S-vacancies (V ) as the catalytic site, potential free-energy pathways to various CO  R products are obtained by means of a computational hydrogen electrode model.

Hydrogen Evolution Reaction at Anion Vacancy of Two-Dimensional Transition-Metal Dichalcogenides: Ab Initio Computational Screening.

The catalytic activity for the hydrogen evolution reaction (HER) at the anion vacancy of 40 2D transition-metal dichalcogenides (TMDs) is investigated using the hydrogen adsorption free energy (Δ G) as the activity descriptor. While vacancy-free basal planes are mostly inactive, anion vacancy makes the hydrogen bonding stronger than clean basal planes, promoting the HER performance of many TMDs. We find that ZrSe and ZrTe have similar Δ G as Pt, the best HER catalyst, at low vacancy density.

An origin of unintentional doping in transition metal dichalcogenides: the role of hydrogen impurities.

We theoretically elucidate the origin of unintentional doping in two-dimensional transition-metal dichalcogenides (TMDs), which has been consistently reported by experiment, but which still remains unclear. Our explanation is based on the charge transfer between TMDs and the underlying SiO in which hydrogen impurities with a negative-U property pin the Fermi level of the SiO as well as adjacent TMD layers. Using first-principles calculations, we obtain the pinning point of the Fermi level from the charge transition level of the hydrogen in the SiO, ε(+/-), and align it with respect to the band-edge positions of monolayer TMDs.

Light-Induced Peroxide Formation in ZnO: Origin of Persistent Photoconductivity.

The persistent photoconductivity (PPC) in ZnO has been a critical problem in opto-electrical devices employing ZnO such as ultraviolet sensors and thin film transistors for the transparent display. While the metastable state of oxygen vacancy (V) is widely accepted as the microscopic origin of PPC, recent experiments on the influence of temperature and oxygen environments are at variance with the V model. In this study, using the density-functional theory calculations, we propose a novel mechanism of PPC that involves the hydrogen-zinc vacancy defect complex (2H-V).

Impaired macrophage autophagy induces systemic insulin resistance in obesity.

Obesity-induced insulin resistance and diabetes are significantly associated with infiltrates of inflammatory cells in adipose tissue. Previous studies recognized the involvement of autophagy in the regulation of metabolism in multiple tissues, including β-cells, hepatocytes, myocytes, and adipocytes. However, despite the importance of macrophages in obesity-induced insulin resistance, the role of macrophage autophagy in regulating insulin sensitivity is seldom addressed.