We report a linear-scaling random Green's function(rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projec...We report a linear-scaling random Green's function(rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H_(2)O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H_(2)O clusters at T = 0 K can reach an error of~ 1 me V per H_(2)O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.展开更多
Metal sulfide is considered as a potential anode for sodium-ion batteries(SIBs),due to the high theoretical capacity,strong thermodynamic stability and low-cost.However,their cycle capacity and rate performance are li...Metal sulfide is considered as a potential anode for sodium-ion batteries(SIBs),due to the high theoretical capacity,strong thermodynamic stability and low-cost.However,their cycle capacity and rate performance are limited by the excessive expansion rate and low intrinsic conductivity.Herein,heterogeneous hollow sphere NiS-Cu_(9)S_(5)/NC(labeled as(NiCu)S/NC)based on Oswald ripening mechanism was prepared through a simple and feasible methodology.From a structural perspective,the hollow structure provides an expansion buffer and raises the electrochemical active area.In terms of electron/ion during the cycles,Na^(+)storage mechanism is optimized by NiS/Cu_(9)S_(5)heterogeneous interface,which increases the storage sites and shortens the migration path of Na^(+).The formation of built-in electric field strengthens the electron/ion mobility.Based on the first principle calculations,it is further proved the formation of heterogeneous interfaces and the direction of electron flow.As the anode for SIBs,the synthesized(NiCu)S/NC delivers high reverse capacity(559.2 mA h g^(-1)at 0.5 A g^(-1)),outstanding rate performance(185.3 mA h g^(-1)at 15 A g^(-1)),long-durable stability(342.6 mA h g^(-1)at 4 A g^(-1)after 1500cycles,150.0 m A h g^(-1)at 10 A g^(-1)after 20,000 cycles with 0.0025%average attenuation rate).The matching cathode electrode Na_(3)V_(2)(PO_(4))_(3)/C is assembled with(NiCu)S/NC for the full-battery that achieves high energy density(253.7 W h kg^(-1))and reverse capacity(288.7 mA h g^(-1)).The present work provides a distinctive strategy for constructing electrodes with excellent capacity and stability for SIBs.展开更多
Twisted graphene multilayers exhibit strongly correlated insulating states and superconductivity due to the presence of ultraflat bands near the charge neutral point.In this paper,the response of ultraflat bands to la...Twisted graphene multilayers exhibit strongly correlated insulating states and superconductivity due to the presence of ultraflat bands near the charge neutral point.In this paper,the response of ultraflat bands to lattice relaxation and a magnetic field in twisted trilayer graphene(tTLG)with different stacking arrangements is investigated by using a full tight-binding model.We show that lattice relaxations are indispensable for understanding the electronic properties of tTLG,in particular,of tTLG in the presence of mirror symmetry.Lattice relaxations renormalize the quasiparticle spectrum near the Fermi energy and change the localization of higher energy flat bands.Furthermore,different from the twisted bilayer graphene,the Hofstadter butterfly spectrum can be realized at laboratory accessible strengths of magnetic field.Our work verifies tTLG as a more tunable platform than the twisted bilayer graphene in strongly correlated phenomena.展开更多
Twisted bilayer graphene(TBG)has taken the spotlight in the condensed matter community since the discovery of correlated phases.In this work,we study heterostructures of TBG and hexagonal boron nitride(hBN)using an at...Twisted bilayer graphene(TBG)has taken the spotlight in the condensed matter community since the discovery of correlated phases.In this work,we study heterostructures of TBG and hexagonal boron nitride(hBN)using an atomistic tight-binding model together with semi-classical molecular dynamics to consider relaxation effects.The hBN substrate has significant effects on the band structure of TBG even in the case where TBG and hBN are not aligned.Specifically,the substrate induces a large mass gap and strong pseudo-magnetic fields that break the layer degeneracy.Interestingly,such degeneracy can be recovered with a second hBN layer.Finally,we develop a continuum model that describes the tight-binding band structure.Our results show that a real-space tight-binding model in combination with semi-classical molecular dynamics is a powerful tool to study the electronic properties of moiréheterostructures,and to explain experimental results in which the effect of the substrate plays an important role.展开更多
Dodecagonal bilayer graphene quasicrystal has 12-fold rotational order but lacks translational symmetry which prevents the application of band theory.In this paper,we study the electronic and optical properties of gra...Dodecagonal bilayer graphene quasicrystal has 12-fold rotational order but lacks translational symmetry which prevents the application of band theory.In this paper,we study the electronic and optical properties of graphene quasicrystal with large-scale tight-binding calculations involving more than ten million atoms.We propose a series of periodic approximants which reproduce accurately the properties of quasicrystal within a finite unit cell.By utilizing the band-unfolding method on the smallest approximant with only 2702 atoms,the effective band structure of graphene quasicrystal is derived.The features,such as the emergence of new Dirac points(especially the mirrored ones),the band gap at M point and the Fermi velocity are all in agreement with recent experiments.The properties of quasicrystal states are identified in the Landau level spectrum and optical excitations.Importantly,our results show that the lattice mismatch is the dominant factor determining the accuracy of layered approximants.The proposed approximants can be used directly for other layered materials in honeycomb lattice,and the design principles can be applied for any quasi-periodic incommensurate structures.展开更多
基金financial support from the National Natural Science Foundation of China (Grant No. 12227901)the financial support from the National Natural Science Foundation of China (Grant Nos. 11974263 and 12174291)。
文摘We report a linear-scaling random Green's function(rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H_(2)O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H_(2)O clusters at T = 0 K can reach an error of~ 1 me V per H_(2)O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.
基金financial supported by the National Natural Science Foundation of China(51572202)the National Nature Science Foundation of Jiangsu Province(BK20221259)Duozhu Technology(Wuhan)Co.,Ltd.
文摘Metal sulfide is considered as a potential anode for sodium-ion batteries(SIBs),due to the high theoretical capacity,strong thermodynamic stability and low-cost.However,their cycle capacity and rate performance are limited by the excessive expansion rate and low intrinsic conductivity.Herein,heterogeneous hollow sphere NiS-Cu_(9)S_(5)/NC(labeled as(NiCu)S/NC)based on Oswald ripening mechanism was prepared through a simple and feasible methodology.From a structural perspective,the hollow structure provides an expansion buffer and raises the electrochemical active area.In terms of electron/ion during the cycles,Na^(+)storage mechanism is optimized by NiS/Cu_(9)S_(5)heterogeneous interface,which increases the storage sites and shortens the migration path of Na^(+).The formation of built-in electric field strengthens the electron/ion mobility.Based on the first principle calculations,it is further proved the formation of heterogeneous interfaces and the direction of electron flow.As the anode for SIBs,the synthesized(NiCu)S/NC delivers high reverse capacity(559.2 mA h g^(-1)at 0.5 A g^(-1)),outstanding rate performance(185.3 mA h g^(-1)at 15 A g^(-1)),long-durable stability(342.6 mA h g^(-1)at 4 A g^(-1)after 1500cycles,150.0 m A h g^(-1)at 10 A g^(-1)after 20,000 cycles with 0.0025%average attenuation rate).The matching cathode electrode Na_(3)V_(2)(PO_(4))_(3)/C is assembled with(NiCu)S/NC for the full-battery that achieves high energy density(253.7 W h kg^(-1))and reverse capacity(288.7 mA h g^(-1)).The present work provides a distinctive strategy for constructing electrodes with excellent capacity and stability for SIBs.
基金supported by the National Natural Science Foundation of China(Grant Nos.11774269,and 12047543)the National Key R&D Program of China(Grant No.2018FYA0305800)+1 种基金the Natural Science Foundation of Hubei ProvinceChina(Grant No.2020CFA041)。
文摘Twisted graphene multilayers exhibit strongly correlated insulating states and superconductivity due to the presence of ultraflat bands near the charge neutral point.In this paper,the response of ultraflat bands to lattice relaxation and a magnetic field in twisted trilayer graphene(tTLG)with different stacking arrangements is investigated by using a full tight-binding model.We show that lattice relaxations are indispensable for understanding the electronic properties of tTLG,in particular,of tTLG in the presence of mirror symmetry.Lattice relaxations renormalize the quasiparticle spectrum near the Fermi energy and change the localization of higher energy flat bands.Furthermore,different from the twisted bilayer graphene,the Hofstadter butterfly spectrum can be realized at laboratory accessible strengths of magnetic field.Our work verifies tTLG as a more tunable platform than the twisted bilayer graphene in strongly correlated phenomena.
基金This work is supported by the National Science Foundation of China(Grant No.11774269 and No.12047543)IMDEA Nanociencia acknowledges support from the“Severo Ochoa"Programme for Centres of Excellence in R&D(Grant No.SEV-2016-0686)+2 种基金P.A.P and F.G.acknowledge funding from the European Commission,within the Graphene Flagship,Core 3,grant number 881603the grant NMAT2D(Comunidad de Madrid,Spain)S.Y.acknowledges funding from the National Key R&D Program of China(Grant No.2018YFA0305800).
文摘Twisted bilayer graphene(TBG)has taken the spotlight in the condensed matter community since the discovery of correlated phases.In this work,we study heterostructures of TBG and hexagonal boron nitride(hBN)using an atomistic tight-binding model together with semi-classical molecular dynamics to consider relaxation effects.The hBN substrate has significant effects on the band structure of TBG even in the case where TBG and hBN are not aligned.Specifically,the substrate induces a large mass gap and strong pseudo-magnetic fields that break the layer degeneracy.Interestingly,such degeneracy can be recovered with a second hBN layer.Finally,we develop a continuum model that describes the tight-binding band structure.Our results show that a real-space tight-binding model in combination with semi-classical molecular dynamics is a powerful tool to study the electronic properties of moiréheterostructures,and to explain experimental results in which the effect of the substrate plays an important role.
基金This work is supported by the National Key R&D Program of China(Grant No.2018FYA0305800)China Postdoctoral Science Foundation(Grant No.2018M632902)MIK acknowledges a support by the JTC-FLAGERA Project GRANSPORT.
文摘Dodecagonal bilayer graphene quasicrystal has 12-fold rotational order but lacks translational symmetry which prevents the application of band theory.In this paper,we study the electronic and optical properties of graphene quasicrystal with large-scale tight-binding calculations involving more than ten million atoms.We propose a series of periodic approximants which reproduce accurately the properties of quasicrystal within a finite unit cell.By utilizing the band-unfolding method on the smallest approximant with only 2702 atoms,the effective band structure of graphene quasicrystal is derived.The features,such as the emergence of new Dirac points(especially the mirrored ones),the band gap at M point and the Fermi velocity are all in agreement with recent experiments.The properties of quasicrystal states are identified in the Landau level spectrum and optical excitations.Importantly,our results show that the lattice mismatch is the dominant factor determining the accuracy of layered approximants.The proposed approximants can be used directly for other layered materials in honeycomb lattice,and the design principles can be applied for any quasi-periodic incommensurate structures.