Abstract Strong interfacial bonding and homogenous dispersion have been found to be necessary conditions take full advantage of the extraordinary properties nanotubes for reinforcement composites. We developed a fully integrated nanotube composite material through use functionalized single‐walled carbon (SWNTs). The functionalization was performed via reaction terminal diamines with alkylcarboxyl groups attached SWNTs in course dicarboxylic acid acyl peroxide treatment. Nanotube‐reinforced...

The fundamental energy gap of a periodic solid distinguishes insulators from metals and characterizes low-energy single-electron excitations. But the in band-structure exact multiplicative Kohn-Sham (KS) potential substantially underestimates gap, major limitation KS density functional theory. Here we give simple proof new theorem: In generalized theory (GKS), band an extended system equals for approximate if GKS operator is continuous change delocalized when electron or hole added. Our...

Van der Waals interactions are ubiquitous in different materials yet not always described properly by current theories. Now, researchers have determined how to accurately and efficiently treat long-range together with other chemical bonds, new findings that important for studies of layered materials.

The origin of ferromagnetism in d;{0} semiconductors is studied using first-principles methods with ZnO as a prototype material. We show that the presence spontaneous magnetization nitrides and oxides sufficient holes an intrinsic property these first-row can be attributed to localized nature 2p states O N. find acceptor doping, especially doping at anion site, enhance much smaller threshold hole concentrations. quantum confinement effect also reduces critical concentration induce nanowires....

We report the energetics and properties of $\ensuremath{\beta}, \ensuremath{\alpha}$, R, $\ensuremath{\gamma}, \ensuremath{\lambda}$, $\ensuremath{\delta}$ polymorphs $\mathrm{MnO}{}_{2}$ within density functional theory, comparing performance recently introduced SCAN with that conventional exchange-correlation functionals experiment. find uniquely yields accurate formation energies across all polymorphs. explain superior based on its satisfaction known constraints appropriate to a semilocal...

Unlike the local density approximation (LDA) and generalized gradient (GGA), calculations with meta-generalized approximations (meta-GGA) are usually done according to Kohn-Sham (gKS) formalism. The exchange-correlation potential of gKS equation is nonmultiplicative, which prevents systematic comparison meta-GGA band structures those LDA GGA. We implement optimized effective (OEP) for periodic systems, allows us carry out in same KS manner as apply OEP several meta-GGAs, including new SCAN...

Abstract The question of material stability is fundamental importance to any analysis system properties in condensed matter physics and materials science. ability evaluate chemical stability, i.e., whether a stoichiometry will persist some environment, structure selection, i.e. what crystal adopt, critical the prediction synthesis, reactivity properties. Here, we demonstrate that density functional theory, with recently developed strongly constrained appropriately normed (SCAN) functional,...

The fluorination of purified HiPco single-wall carbon nanotubes to a stoichiometry CFx (x ⩽ 0.2) followed by pyrolysis the partially fluorinated up 1000 °C was found have “cut” range short lengths (average <50 nm). process monitored in-situ with TGA-FTIR. fluorine driven off nanotube structure in form COF2 and CF4. been characterized Raman, ATR-IR, EDAX, AFM measurements. Short bundles composed strongly interacting individual were sample. specific reactivities should lead novel applications...

The structural and energetic properties of layered materials propose a challenge to density functional theory with common semilocal approximations the exchange-correlation. By combining most-widely used generalized gradient approximation (GGA), Perdew--Burke--Ernzerhof (PBE), revised Vydrov--Van Voorhis non-local correlation (rVV10), both excellent 28 were recovered judicious parameter selection. We term resulting as PBE+rVV10L "L" denoting for materials. Such combination is not new,...

Using first-principles electronic structure calculations we find that the titanium vacancy and divacancy may be responsible for unexpected ferromagnetism in undoped anatase ${\text{TiO}}_{2}$. An isolated produces a magnetic moment of $3.5{\ensuremath{\mu}}_{B}$, an $2.0{\ensuremath{\mu}}_{B}$. The origin collective moments is holes introduced by or narrow nonbonding oxygen $2{p}_{\ensuremath{\pi}}$ band. At center divacancy, ${\text{O}}_{2}$ dimer forms during relaxation, which lowers total...

Next-generation thin film solar cell technologies require earth abundant photovoltaic absorber materials. Here we demonstrate an alternative approach to design of such materials, evaluating candidates grouped by constituent elements rather than underlying crystal structures. As example, evaluate thermodynamic stability, electrical transport, electronic structure, optical and defect properties Cu-Sn-S using complementary theory experiment. We conclude that Cu2SnS3 avoids many issues...

Recent revisions of defect formation energy calculations based on bandgap corrected hybrid functionals have raised concerns about the validity earlier results standard density and reliability theoretical prediction electrical properties in semiconductor materials general. We show here that a close agreement between two types can be achieved by determining appropriate values for electronic atomic reference energies, thereby mitigating uncertainties associated with choice underlying functional.

We report that the refractive index of transition metal dichacolgenide (TMDC) monolayers, such as MoS2, WS2, and WSe2, can be substantially tuned by > 60% in imaginary part 20% real around exciton resonances using CMOS-compatible electrical gating. This giant tunablility is rooted dominance excitonic effects monolayers strong susceptibility excitons to influence injected charge carriers. The tunability mainly results from carriers broaden spectral width interband transitions facilitate...

Transition-metal oxides with partially filled $d$ shells are typically Mott or charge-transfer insulators notoriously poor transport properties due to large effective electron/hole masses carrier self-trapping. Employing band-structure calculations and ab initio small-polaron theory for MnO Fe${}_{2}$O${}_{3}$, we explore the potential of ${d}^{5}$ achieving desirable semiconducting properties, e.g., in solar energy applications. The quantification self-trapping energies trends coordination...

Discovery of novel semiconducting materials is needed for solar energy conversion and other optoelectronic applications. However, emerging low‐dimensional absorbers often have unconventional crystal structures unusual combinations optical absorption electrical transport properties, which considerably slows down the research development progress. Here, effect stronger weaker carrier collection 2D‐like absorber are studied using a high‐throughput combinatorial experimental approach,...

Adsorption of the molecule CO on metallic surfaces is an important unsolved problem in Kohn-Sham density functional theory (KS-DFT). We present a detailed study carbon monoxide adsorption fcc (111) $3d, 4d$, and $5d$ metals using nonempirical semilocal functionals for exchange-correlation energy: local-density approximation (LDA), two generalized gradient approximations or GGAs [Perdew-Burke-Ernzerhof (PBE) PBE solids (PBEsol)], meta-GGA [strongly constrained appropriately normed (SCAN)...

We study the electronic structures and magnetic properties of anatase TiO2 doped with 3d transition metals (V, Cr, Mn, Fe, Co, Ni), using first-principles total energy calculations based on density functional theory (DFT). Using a molecular-orbital bonding model, are well understood. A band coupling model d–d level repulsions between dopant ions is proposed to understand chemical trend ordering. Ferromagnetism found be stabilized in V-, Cr-, Co-doped samples if there no other carrier native...

By sequential growth of the core and shell different materials, ZnO/ZnS ZnO/MgO core/shell nanowire arrays are fabricated. Photoluminescence properties these samples with thicknesses studied in detail. The results indicate that ZnS thickness as a function treatment time will noticeably change photoluminescence intensity ZnO nanowires, whereas MgO not any more after it saturates surface dangling bonds core. Large-scale first-principles calculations that, unlike electrons holes which both...

Understanding the electronic structure and transport properties of doped PbSe for its thermoelectric applications is an urgent need. Using a first-principles approach, we first explore band structures with series impurities, including cation-site substitutional impurities (Na, K, Rb; Mg, Ca, Sr; Cu, Ag, Au; Zn, Cd, Hg; Ga, In, Tl; Ge, Sn; As, Sb, Bi) anion-site (P, Sb; O, S, Te). Then calculate density states (DOS) difference between samples pure host sample, which useful quantity to...

Abstract To accelerate the design and discovery of novel functional materials, here, p‐type transparent conducting oxides, an inverse approach is formulated, integrating three steps: i) articulating target properties selecting initial pool candidates based on “design principles”, ii) screening this by calculating “selection metrics” for each member, iii) laboratory realization more‐detailed theoretical validation remaining “best‐of‐class” materials. Following a principle that suggests using...

Significance We propose, and preliminarily confirm with experiments, a theoretical model to understand various structure–performance dependences of layered-structure birnessite as an oxygen evolution reaction (OER) catalyst. Besides the well-accepted importance Mn(III), we emphasize critical nonuniform distribution Mn(III) OER catalytic activity. Such contributes reduction overpotential by building internal potential step. further propose small polaron common concept link fields catalysis...

The design of thermoelectric materials often involves the integration point defects (alloying) as a route to reduce lattice thermal conductivity. Classically, defect scattering strength follows from simple considerations such mass contrast and presence induced strain fields (e.g. radius contrast, coordination changes). While can be easily calculated, associated by chemistry are not readily predicted poorly understood. In this work, we use classical first principles calculations provide...