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Sheng-Li Zhang

Publications and source records attributed to Sheng-Li Zhang.

6 recordsLinked to original sources
arXiv2020

Borophosphene as a promising Dirac anode with large capacity and high-rate capability for sodium-ion batteries

Sodium-ion batteries (SIBs) have attracted a great deal of attention as potential low-cost energy storage alternatives to Lithium-ion batteries (LIBs) due to the intrinsic safety and great abundance of sodium on Earth. For developing competitive SIBs, highly efficient anode materials with large capacity and rapid ion diffusion are indispensable. In this study, a two-dimensional (2D) Dirac monolayer, that is borophosphene, is proposed to be a promising anode material for high performance SIBs on the basis of density functional theory calculations. The performances of Na adsorption and diffusion, maximum specific capacity, open circuit voltage, cyclical stability and electronic properties combined with Bader charge analysis are explored. It is found that the borophosphene can spontaneously adsorb Na atom with binding energy of -0.838 eV. A low diffusion energy barrier of 0.221 eV suggests rapid ion conductivity. More intriguingly, a maximum specific capacity of 1282 mAh/g can be achieved in borophosphene, which is one of the largest values reported in 2D anode materials for SIBs. A low average voltage of 0.367 V is estimated, implying a suitable voltage of the anode material. Metallic properties, tiny surface expansion, and good kinetic stability of sodiated borophosphene give rise to high electrical conductivity and favorable cyclability. These advantages above suggest the borophosphene can be used as a Dirac anode material for SIBs with excellent performances of large specific capacity, high-rate capability, and favorable cyclability.

cond-mat.mtrl-sci↗
arXiv2019

Borophosphene: a New Anisotropic Dirac Cone Monolayer with High Fermi Velocity and Unique Feature of Self-doping

Two-dimensional (2D) Dirac cone materials exhibit linear energy dispersion at the Fermi level, where the effective masses of carriers are very close to zero and the Fermi velocity is ultrahigh, only 2 ~ 3 orders of magnitude lower than the light velocity. Such the Dirac cone materials have great promise in high-performance electronic devices. Herein, we have employed the genetic algorithms methods combining with first-principles calculations to propose a new 2D anisotropic Dirac cone material, that is, orthorhombic boron phosphide (BP) monolayer named as borophosphene. Molecular dynamics simulation and phonon dispersion have been used to evaluate the dynamic and thermal stability of borophosphene. Because of the unique arrangements of B-B and P-P dimers, the mechanical and electronic properties are highly anisotropic. Of great interest is that the Dirac cone of the borophosphene is robust, independent of in-plane biaxial and uniaxial strains, and can also be observed in its one-dimensional (1D) zigzag nanoribbons and armchair nanotubes. The Fermi velocities are ~ 105 m/s, the same order of magnitude with that of graphene. By using a tight-binding model, the origin of the Dirac cone of borophosphene is analyzed. Moreover, a unique feature of self-doping can be induced by the in-plane biaxial and uniaxial strains of borophosphene and the Curvature effect of nanotubes, which is great beneficial to realizing high speed carriers (holes). Our results suggest that the borophosphene holds a great promise in high-performance electronic devices, which could promote the experimental and theoretical studies to further explore the potential applications of other 2D Dirac cone sheets.

cond-mat.mtrl-sci↗
arXiv2017

Enhanced visible light absorption in ZnO/GaN heterostructured nanofilms

ZnO/GaN alloys exhibit exceptional photocatalyst applications owing to the flexibly tunable band gaps that cover a wide range of the solar spectrum, and thus have attracted extensive attentions over the past few years. In this study, first-principles calculations were employed to investigate structural stabilities and electronic properties of (1-100) and (11-20) ZnO/GaN heterostructured nanofilms. The effects of nanofilm thickness and GaN ratio were explored. It was found that all studied heterostructured nanofilms were less stable than the corresponding pure ZnO film but more stable than pure GaN one, exhibiting a much thicker film with better stability. Electronic band structures displayed that both two types of (1-100) and (11-20) heterostructured nanofilms were semiconductors with band gaps strongly depending on the GaN ratios as well as the thicknesses. Of particular interesting is that the band gaps decreased firstly, and then increased with the increasing GaN ratio. Furthermore, electronic contribution to the valence band maximum and the conduction band minimum, and optical absorption were discussed. Our results of ZnO/GaN heterostructured nanofilms with spatial separation of electrons and holes, and flexibly tunable band gaps hold great promise for applications in visible-photovoltaic field.

cond-mat.mtrl-sci↗
arXiv2016

New localization mechanism and Hodge duality for $q-$form field

In this paper, we investigate the problem of localization and the Hodge duality for a $q-$form field on a $p-$brane with codimension one. By a general Kaluza-Klein (KK) decomposition without gauge fixing, we obtain two Schrödinger-like equations for two types of KK modes of the bulk $q-$form field, which determine the localization and mass spectra of these KK modes. It is found that there are two types of zero modes (the $0-$level modes): a $q-$form zero mode and a $(q-1)-$form one, which cannot be localized on the brane at the same time. For the $n-$level KK modes, there are two interacting KK modes, a massive $q-$form KK mode and a massless $(q-1)-$form one. By analyzing gauge invariance of the effective action and choosing a gauge condition, the $n-$level massive $q-$form KK mode decouples from the $n-$level massless $(q-1)-$form one. It is also found that the Hodge duality in the bulk naturally becomes two dualities on the brane. The first one is the Hodge duality between a $q-$form zero mode and a $(p-q-1)-$form one, or between a $(q-1)-$form zero mode and a $(p-q)-$form one. The second duality is between two group KK modes: one is an $n-$level massive $q-$form KK mode with mass $m_n$ and an $n-$level massless $(q-1)-$form mode; another is an $n-$level $(p-q)-$form one with the same mass $m_n$ and an $n-$level massless $(p-q-1)-$form mode. Because of the dualities, the effective field theories on the brane for the KK modes of the two dual bulk form fields are physically equivalent.

hep-th↗
arXiv2014

Localization of $q-$form fields on $AdS_{p+1}$ branes

In this paper, we investigate localization of a free massless $q-$form bulk field on thin and thick $AdS_{p+1}$ branes with codimension one. It is found that the zero mode of the $q-$form field with $q>(p+2)/2$ can be localized on the thin negative tension brane, which is different from the flat brane case given in [JHEP 10 (2012) 060]. For the thick $AdS_{p+1}$ branes, the $q-$form field with $q>(p+2)/2$ also has a localized zero mode under some conditions. Furthermore, we find that there are massive bound KK modes of the $q-$form field, which are localized on this type $p-$branes.

hep-th↗