arXiv subjects

Shih-Yang Lin

Publications and source records attributed to Shih-Yang Lin.

At least 19 recordsLinked to original sources

arXiv2021

Essential properties of AlCl4-related graphite intercalation compounds of aluminum-ion-based battery cathodes

Up to now, many guest atoms/molecules/ions have been successfully synthesized into graphite to form the various compounds. For example, alkali-atom graphite intercalation compounds are verified to reveal the stage-n structures, including LiC6n and LiM8n [M=K. Rb and Cs; n=1, 2, 3; 4]. On the other side, AlCl4-ion/molecule ones are examined to show stage-4 and stage-3 cases at room and lower temperatures, respectively. Stage-1 and stage-2 configurations, with the higher intercalant concentrations, are unable to synthesize in experimental laboratories. This might arise from the fact that it is quite difficult to build the periodical arrangements along the longitudinal z and transverse directions simultaneously for the large ions or molecules. Our works are mainly focused on stage-1 and stage-2 systems in terms of geometric and electronic properties. The critical features, being associated with the atom-dominated energy spectra and wave function within the specific energy ranges, the active multi-orbital hybridization in distinct chemical bonds, and atom- & orbital-decomposed van Hove singularities, will be thoroughly clarified by the delicate simulations and analyses.

cond-mat.mtrl-sci↗

arXiv2020

Essential electronic properties on stage-1 Li/Li+-graphite-intercalation compounds for different concentrations

We use first-principles calculation within the density functional theory (DFT) to explore the electronic properties on stage-1 Li- and Li+-graphite-intercalation compounds (GIC) for different concentrations, LiCx/Li+Cx with x= 6,12,18,24,32 and 36. The essential properties, e.g. geometric structures, band structures and spatial charge distributions are determined by the hybridization of orbitals, the main focus of our works. The band structures/density of states/spatial charge distribution display that the Li-GIC possesses blue shift of fermi energy and just like metals, but the Li+-GIC still preserves as original graphite or so-call semimetal possessing the same densities of free electrons and holes. According to these properties, we find that there exists weak but significant van der Waals interactions between interlayer of graphite, and 2s-2pz hybridization between Li and C. There scarcely exists strong interactions between Li+-C. The dominant interaction between the Li and C is 2s-2pz orbital-orbital couple; the orbital-orbital couple is not significant in Li+ and C case but the dipole-diploe couple.

cond-mat.mtrl-sci↗

arXiv2019

Stacking-configuration-enriched essential properties in bilayer silicenes

The geometric, electronic and magnetic properties of silicene-related systems present the diversified phenomena through the first-principles calculations. The critical factors, the group-IV monoelements, buckled/planar structures, stacking configurations, layer numbers, and van der Waals interactions of bilayer composites are taken into account simultaneously. The developed theoretical framework is responsible for the concise physical and chemical pictures. The delicate evaluations and analyses are conducted on the optimal lattices, the atom- $\&$ spin-dominated energy bands, the atom-, orbital- $\&$ spin-projected vanHove singularities, and the magnetic moments. Most importantly, they achieve the decisive mechanisms, the buckled/planar honeycomb lattices, the multi-/single-orbital hybridizations, and the significant/negligible spin-orbital couplings. Furthermore, we investigate the stacking-configuration-induced dramatic transformations of the essential properties by the relative shift in bilayer graphene and silicene. The lattice constant, interlayer distance, the buckle height, and the total energy essentially depend on the magnitude and direction of the relative shift: AA $\rightarrow$ AB $\rightarrow$ AA$^{\prime}$ $\rightarrow$ AA. Apparently, sliding bilayer systems are quite different between silicene and graphene in terms of electronic properties, strongly depending on the buckled/planar honeycomb lattices, the multi-/single-orbital hybridizations, the dominant/observable interlayer hopping integrals, and the significant/negligible spin interactions. The predicted results can account for the up-to-date experimental measurements.

cond-mat.mtrl-sci↗

arXiv2019

Enrich properties of Li+-based battery anode: Li_4Ti_5O_12

The 3D ternary Li_4Ti_5O_12, the Li+-based battery anode, presents the unusual lattice symmetry (a triclinic crystal), band structure, charge density, and density of states, under the first-principles calculations. It belongs to a large direct-gap semiconductor of E_g^d~ 2,98 eV. The atom-dominated valence and conduction bands, the spatial charge distribution and the atom- and orbital-decomposed van Hove singularities are available in the delicate identifications of multi-orbital hybridizations in Li-O and Ti-O bonds. The extremely non-uniform chemical environment, which induce the very complicated hopping integrals, directly arise from the large bonding fluctuations and the highly anisotropic configurations. Also, the developed theoretical framework is very useful for fully understanding the cathodes and electrolytes of oxide compounds.

cond-mat.mtrl-sci↗

arXiv2019

Diversified properties of carbon substitutions in silicene

The theoretical framework, which is built from the first-principles results, is successfully developed for investigating emergent two-dimensional (2D) materials, as it is clearly illustrated by carbon substitution in silicene. Computer coding with the aid of VASP in conjunction with data analysis from the multi-orbital hybridizations [spin configurations] are thoroughly identified from the optimal honeycomb lattices, the atom-dominated energy spectra, and the spatial charge density distributions. The atom and orbital-decomposed van Hove singularities [the net magnetic moments], being very sensitive to the concentration and arrangements of guest atoms. All the binary 2D silicon-carbon compounds belong to the finite- or zero-gap semiconductors, corresponding to the thoroughly/strongly/slightly modified Dirac-cone structures near the Fermi level. Additionally, there are frequent {\pi} and {\sigma} band crossings, but less anti-crossing behaviors. Apparently, our results indicate the well-defined {\pi} and {\sigma} bondings.

physics.comp-ph↗

arXiv2019

Diverse quantization phenomena in layered materials

The diverse quantization phenomena in 2D condensed-matter systems, being due to a uniform perpendicular magnetic field and the geometry-created lattice symmetries, are the focuses of this book. They cover the diversified magneto-electronic properties, the various magneto-optical selection rules, the unusual quantum Hall conductivities, and the single- and many-particle magneto-Coulomb excitations. The rich and unique behaviors are clearly revealed in few-layer graphene systems with the distinct stacking configurations, the stacking-modulated structures, and the silicon-doped lattices, bilayer silicene/germanene systems with the bottom-top and bottom-bottom buckling structures, monolayer and bilayer phosphorene systems, and quantum topological insulators. The generalized tight-binding model, the static and dynamic Kubo formulas, and the random-phase approximation, are developed/modified to thoroughly explore the fundamental properties and propose the concise physical pictures. The different high-resolution experimental measurements are discussed in detail, and they are consistent with the theoretical predictions.

physics.comp-ph↗

arXiv2019

Fundamental properties of transition-metals-adsorbed graphene

The revealing properties of transition metal (T)-doped graphene systems are investigated with the use of the first-principles method. The detailed calculations cover the bond length, position and height of adatoms, binding energy, atom-dominated band structure, adatom-induced free carrier density as well as energy gap, spin-density distributions, spatial charge distribution, and atom-, orbital- and spin-projected density-of-states (DOS). The magnetic configurations are clearly identified from the total magnetic moments, spin-split energy bands, spin-density distributions and spin-decomposed DOS. Moreover, the single- or multi-orbital hybridizations in T-C, T-T, and C-C bonds can be accurately deduced from the careful analyses of the above-mentioned physical quantities. They are responsible for the optimal geometric structure, the unusual electronic properties, as well as the diverse magnetic properties. All the doped systems are metals except for the low-concentration Ni-doped ones with semiconducting behavior. In contrast, ferromagnetism is exhibited in various Fe/Co-concentrations but only under high Ni-concentrations. Our theoretical predictions are compared with available experimental data, and potential applications are also discussed.

cond-mat.mtrl-sci↗

arXiv2018

Essential properties of Li/Li$^+$ graphite intercalation compounds

The essential properties of graphite-based 3D systems are thoroughly investigated by the first-principles method. Such materials cover a simple hexagonal graphite, a Bernal graphite, and the stage-1 to stage-4 Li/Li$^+$ graphite intercalation compounds. The delicate calculations and the detailed analyses are done for their optimal stacking configurations, bong lengths, interlayer distances, free electron $\&$ hole densities, Fermi levels, transferred charges in chemical bondings, atom- or ion-dominated energy bands, spatial charge distributions and the significant variations after intercalation, Li-/Li$^+$- $\&$ C-orbital-decomposed DOSs. The above-mentioned physical quantities are sufficient in determining the critical orbital hybridizations responsible for the unusual fundamental properties. How to dramatically alter the low-lying electronic structures by modulating the quest-atom/quest-ion concentration is one of focuses, e.g., the drastic changes on the Fermi level, band widths, and number of energy bands. The theoretical predictions on the stage-n-dependent band structures could be examined by the high-resolution angle-resolved photoemission spectroscopy (ARPES). Most important, the low-energy DOSs near the Fermi might provide the reliable data for estimating the free carrier density due to the interlayer atomic interactions or the quest-atom/quest-ion intercalation. The van Hove singularities, which mainly arise from the critical points in energy-wave-vector space, could be directly examined by the experimental measurements of scanning tunneling spectroscopy (STS). Their features should be very useful in distinguishing the important differences among the stage-$n$ graphite intercalation compounds, and the distinct effects due to the atom or ion decoration.

cond-mat.mtrl-sci↗

arXiv2018

Structure- and adatom-enriched essential properties of graphene nanoribbons

A systematic study is made on geometric, electronic and magnetic properties of one-dimensional graphene nanoribbons using the first-principles calculations. The feature-rich essential properties result from the various orbital hybridizations in chemical bonds and the edge-carbon- and adatom-induced spin states. Pristine nanoribbons, with honeycomb lattices, can exhibit the planar, curving, scrolling, folding, and stacking configurations. Adatom adsorptions on surface and edge, respectively, create the buckled structures and the non-hexagonal/non-planar edges. There exist six kinds of of spin-dependent electronic and magnetic properties, non-magnetic, ferromagnetic and anti-ferromagnetic metals, the non-magnetic semiconductors, and the anti-ferromagnetic semiconductors with/without the spin splitting. They are clearly illustrated by the energy gaps, the electron/hole densities, the net magnetic moment, the atom-dominated energy bands, the spatial charge distributions, the spin arrangements, and the orbital- and spin-projected density of states. The diverse essential properties are determined by the complicated relations among the finite-size confinement, edge structure, curvature effect, interlayer atomic interaction, spin configuration, and chemical adsorption. The theoretical predictions can provide the full information in potential applications, and part of them agree with the recent experimental measurements.

cond-mat.mes-hall↗

arXiv2017

Fluorination-Enriched Electronic and Magnetic Properties in Graphene Nanoribbons

The feature-rich electronic and magnetic properties of fluorine-doped graphene nanoribbons are investigated by the first-principles calculations. They arise from the cooperative or competitive relations among the significant chemical bonds, finite-size quantum confinement and edge structure. There exist C-C, C-F, and F-F bonds with the multi-orbital hybridizations. Fluorine adatoms can create the p-type metals or the concentration- and distribution-dependent semiconductors, depending on whether the $\pi$ bonding is seriously suppressed by the top-site chemical bonding. Furthermore, five kinds of spin-dependent electronic and magnetic properties cover the non-magnetic and ferromagnetic metals, the non-magnetic semiconductors, and the anti-ferromagnetic semiconductors with/without the spin splitting. The diverse essential properties are clearly revealed in the spatial charge distribution, the spin density, and the orbital-projected density of states.

cond-mat.mes-hall↗

arXiv2017

Geometric and electronic properties of graphene-related systems: Chemical bondings

This work presents a systematic review of the feature-rich essential properties in graphene-related systems using the first-principles method. The geometric and electronic properties are greatly diversified by the number of layers, the stacking configurations, the sliding-created configuration transformation, the rippled structures, and the distinct adatom adsorptions. The top-site adsorptions can induce the significantly buckled structures, especially for hydrogen and fluorine adatoms. The electronic structures consist of the carbon-, adatom- and (carbon, adatom)-dominated energy bands. There exist the linear, parabolic, partially flat, sombrero-shaped and oscillatory band, accompanied with various kinds of critical points. The semi-metallic or semiconducting behaviors of graphene systems are dramatically changed by the multi- or single-orbital chemical bondings between carbons and adatoms. Graphene oxides and hydrogenated graphenes possess the tunable energy gaps. Fluorinated graphenes might be semiconductors or hole-doped metals, while other halogenated systems belong to the latter. Alkali- and Al-doped graphenes exhibit the high-density free electrons in the preserved Dirac cones. The ferromagnetic spin configuration is revealed in hydrogenated and halogenated graphenes under certain distributions. Specifically, Bi nano-structures are formed by the interactions between monolayer graphene and buffer layer. Structure and adatom-enriched essential properties are compared with the measured results, and potential applications are also discussed.

physics.chem-ph↗

arXiv2016

Alkali-induced rich properties in graphene nanoribbons: Chemical bonding

The alkali-adsorbed graphene nanoribbons exhibit the feature-rich electronic and magnetic properties. From the first-principles calculations, there are only few adatom-dominated conduction bands, and the other conduction and valence bands are caused by carbon atoms. A lot of free electrons are revealed in the occupied alkali- and carbon-dependent conduction bands. Energy bands are sensitive to the concentration, distribution and kind of adatom and the edge structure, while the total linear free carrier density only relies on the first one. These mainly arise from a single $s-2p_z$ orbital hybridization in the adatom-carbon bond. Specifically, zigzag systems can present the anti-ferromagnetic ordering across two edges, ferromagnetic ordering along one edge and non-magnetism, being reflected in the edge-localized energy bands with or without spin splitting. The diverse energy dispersions contribute many special peaks in density of states. The critical chemical bonding and the distinct spin configuration could be verified from the experimental measurements.

cond-mat.mes-hall↗

arXiv2016

Feature-rich electronic properties of aluminum-doped graphenes

The electronic properties of aluminum-doped graphenes enriched by multi-orbital hybridizations are investigated using first-principles calculations. The feature-rich electronic structures exhibit the quasi-rigid red shifts of the carbon-created energy bands, the Al-dominated valence and conduction bands, and many free electrons in the conduction Dirac cone. These are directly reflected in the special structures of density of states (DOS). The Al- and alkali-induced high free carrier densities are almost the same. There exist certain important differences among the Al-, alkali- and halogen-doped grapehenes, such as, the buckled or planar graphene, the preserved or seriously distorted Dirac cone, the existence of the adatom-dominated valence bands, the free electrons or holes, the degenerate or splitting spin-related states, and the simple or complicated peaks in DOS. The similarities and differences mainly come from the diverse orbital hybridizations in adatom-C bonds, as indicated from the atom-dominated bands, the spatial charge distributions and the orbital-projected DOS.

cond-mat.mtrl-sci↗

arXiv2015

$\pi$-bonding-dominated energy gaps in graphene oxides

Chemical bondings of graphene oxides with oxygen concentration from 1\% to 50\% are investigated using first-principle calculations. Energy gaps are mainly determined by the competition of orbital hybridizations in C-C, O-O, and C-O bonds. They are very sensitive to the changes in oxygen concentration and distributions. There exists five types of $\pi$ bondings during the variation from the full to vanishing adsorptions, namely the complete termination, the partial suppression, the 1D bonding, the deformed planar bonding, and the well-behaved one. They can account for the finite and gapless characteristics, corresponding to the O-concentrations of $>$25\% and $<$3\%, respectively. The feature-rich chemical bondings dominate band structures and density of states, leading to diverse electronic properties.

cond-mat.mtrl-sci↗

arXiv2015

Magnetoelectronic and optical properties of nonuniform graphene nanoribbons

The electronic and optical properties of nonuniform bilayer graphene nanoribbons are worth investigating as they exhibit rich magnetic quantization. Based on our numerical results, their electronic and optical properties strongly depend on the competition between magnetic quantization, lateral confinement, and stacking configuration. The results of our calculations lead to four categories of magneto-electronic energy spectra, namely monolayer-like, bilayer-like, coexistent, and irregular quasi-Landau-level like. Various types of spectra described in this paper are mainly characterized by unusual spatial distributions of wave functions in the system under study. In our paper, we demonstrate that these unusual quantized modes lead to the appearance of such diverse magneto-optical spectra. Moreover, the investigation of the density of states in our model leads to the appearance of many prominent symmetric and weakly asymmetric peaks. The almost well-behaved quasi-Landau levels exhibit high-intensity peaks with specific selection rules, and the distorted energy subbands present numerous low-intensity peaks without any selection rules.

physics.comp-ph↗

arXiv2015

Configuration- and concentration-dependent electronic properties of hydrogenated graphene

The electronic properties of hydrogenated graphenes are investigated with the first-principles calculations. Geometric structures, energy bands, charge distributions, and density of states (DOS) strongly depend on the different configurations and concentrations of hydrogen adatoms. Among three types of optimized periodical configurations, only in the zigzag systems the band gaps can be remarkably modulated by H-concentrations. There exist middle-gap semiconductors, narrow-gap semiconductors, and gapless systems. The band structures exhibit the rich features, including the destruction or recovery of the Dirac-cone structure, newly formed critical points, weakly dispersive bands, and (C,H)-related partially flat bands. The orbital-projected DOS are evidenced by the low-energy prominent peaks, delta-function-like peaks, discontinuous shoulders, and logarithmically divergent peaks. The DOS and spatial charge distributions clearly indicate that the critical bondings in C-C and C-H is responsible for the diversified properties.

cond-mat.mtrl-sci↗

arXiv2015

Chemical Bondings Induced Rich Electronic Properties of Oxygen Absorbed Few-layer Graphenes

Electronic properties of graphene oxides enriched by the strong chemical bondings are investigated using first-principle calculations. They are very sensitive to the changes in the number of graphene layer, stacking configuration, and distribution of oxygen. The feature-rich electronic structures exhibit the destruction or distortion of Dirac cone, opening of band gap, anisotropic energy dispersions, O- and (C,O)-dominated energy dispersions, and extra critical points. All the few-layer graphene oxides are semi-metals except for the semiconducting monolayer ones. For the former, the distorted Dirac-cone structures and the O-dominated energy bands near the Fermi level are revealed simultaneously. The orbital-projected density of states (DOS) have many special structures mainly coming from a composite energy band, the parabolic and partially flat ones. The DOS and spatial charge distributions clearly indicate the critical bondings in O-O, C-O and C-C bonds, being responsible for the diversified properties.

cond-mat.mtrl-sci↗

arXiv2015

H-Si bonding-induced unusual electronic properties of silicene: a method to identify hydrogen concentration

Hydrogenated silicenes possess peculiar properties owing to the strong H-Si bonds, as revealed by an investigation using first principles calculations. The various charge distributions, bond lengths, energy bands, and densities of states strongly depend on different hydrogen configurations and concentrations. The competition of strong H-Si bondings and weak sp3 hybridization dominate the electronic properties. Chair configurations belong to semiconductors, while the top configurations show a nearly dispersionless energy band at the Fermi level. Both two systems display H-related partially flat bands at middle energy, and recovery of low-lying \pi bands during the reduction of concentration. Their densities of states exhibit prominent peaks at middle energy, and the top systems have a delta-funtion-like peak at E=0. The intensity of these peaks are gradually weakened as the concentration decreases, providing an effective method to identify the H-concentration in scanning tunneling spectroscopy experiments.

cond-mat.mtrl-sci↗