The COVID-19 pandemic has underscored the critical need for rapid and accurate diagnostic tools.Current methods,including Polymerase Chain Reaction and rapid antigen tests(RAT),have limitations in speed,sensitivity,an...The COVID-19 pandemic has underscored the critical need for rapid and accurate diagnostic tools.Current methods,including Polymerase Chain Reaction and rapid antigen tests(RAT),have limitations in speed,sensitivity,and the requirement for specialized equipment and trained personnel.Nanotechnology,particularly upconversion nanoparticles(UCNPs),offer a promising alternative due to their unique optical properties.UCNPs can convert low-energy near-infrared light into higher-energy visible light,making them ideal for use as optical probes in single molecule detection and point of care applications.This study,initiated in early 2020,explores the opportunity of using highly doped UCNPs(40%Yb^(3+)/4%Er^(3+))in lateral flow assay(LFA)for the early diagnosis of COVID-19.The UCNPsbased LFA testing demonstrated a minimum detection concentration of 100 pg/mL for SARS-CoV-2 antigen and 10^(5)CCID_(50)/mL for inactivated virus.Clinical trials,conducted in Malaysia and Western Australia independently,showed that the technique was at least 100 times more sensitive than commercial RAT kits,with a sensitivity of 100%and specificity of 91.94%.The development process involved multidisciplinary collaborations,resulting in the Virulizer device,an automated strip reader for point-of-care testing.This work sets a reference for future development of highly sensitive and quantitative RAT,aiming for the Limits of Detection in the range of sub-ng/mL.展开更多
A facile,one-pot,urea solution combustion route was utilized to synthesize highly catalytic CeO2 nanostructures.CeO2 prepared under varying thermal conditions was characterized by electron microscopy,energy dispersive...A facile,one-pot,urea solution combustion route was utilized to synthesize highly catalytic CeO2 nanostructures.CeO2 prepared under varying thermal conditions was characterized by electron microscopy,energy dispersive X-ray spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,infrared and Raman techniques.As the synthesis temperature is raised from 400 to 1000℃,the crystallite size and dspacing of nanoparticles are observed to reduce while cell parameters remain in the same range.Particle size exhibits an accession from~20 to~50 nm along the process.Initial CeO2 nanoparticles are detected as a composite structure of CeO2 and graphitic carbon nitride(g-C3 N4)produced by the pyrolysis of urea.Concerning the solid carbon particulate oxidation capacity,an outstanding performance is exhibited by CeO2 synthesized at 800℃where the oxidation onset temperature is reduced by 27%compared with the others.The superior performance is attributed to the carbon nitride-generated unique CeO2 nanomorphology consolidating ample reactive sites and facilitated oxygen delivery for a highly efficient thermocatalytic process.Concerning atmospheric pollution mitigation,synthesis of these CeO2 nanostructures represents a cost effective and convenient abatement technique for carbon particulates in comparison to cost-intensive,environmentally detrimental and noble-metal based techniques.展开更多
We conduct a systematic investigation of the role of Hubbard U corrections in electronic structure calculations of two-dimensional(2D)materials containing 3d transition metals.Specifically,we use density functional th...We conduct a systematic investigation of the role of Hubbard U corrections in electronic structure calculations of two-dimensional(2D)materials containing 3d transition metals.Specifically,we use density functional theory(DFT)with the PBE and PBE+U approximations to calculate the crystal structure,band gaps,and magnetic parameters of 638 monolayers.Based on a comprehensive comparison to experiments we first establish that the inclusion of the U correction worsens the accuracy for the lattice constants.Consequently,PBE structures are used for subsequent property evaluations.The band gaps show a significant dependence on U.In particular,for 134(21%)of the materials the U parameter induces a metal-to-insulator transition.For the magnetic materials we calculate the magnetic moment,magnetic exchange coupling,and magnetic anisotropy parameters.In contrast to the band gaps,the size of the magnetic moments shows only weak dependence on U.Both the exchange energies and magnetic anisotropy parameters are systematically reduced by theU correction.On this basis we conclude that the Hubbard U correction will lead to lower predicted Curie temperatures in 2D materials.All the calculated properties are available in the Computational 2D Materials Database(C2DB).展开更多
We introduce and discuss a method for global optimization of atomic structures based on the introduction of additional degrees of freedomdescribing:1)the chemical identities of the atoms,2)the degree of existence of t...We introduce and discuss a method for global optimization of atomic structures based on the introduction of additional degrees of freedomdescribing:1)the chemical identities of the atoms,2)the degree of existence of the atoms,and 3)their positions in a higher-dimensional space(4-6 dimensions).The new degrees of freedom are incorporated in a machine-learning model through a vectorial fingerprint trained using density functional theory energies and forces.The method is shown to enhance global optimization of atomic structures by circumvention of energy barriers otherwise encountered in the conventional energy landscape.The method is applied to clusters as well as to periodic systems with simultaneous optimization of atomic coordinates and unit cell vectors.Finally,we use the method to determine the possible structures of a dual atomcatalyst consisting of a Fe-Co pair embedded in nitrogen-doped graphene.展开更多
In the recent years, transition-metal dichalcogenides such as MoS2 have attracted considerable attention owing to their unique structure and electronic properties. Chemical vapor deposition （CVD） is a popular method...In the recent years, transition-metal dichalcogenides such as MoS2 have attracted considerable attention owing to their unique structure and electronic properties. Chemical vapor deposition （CVD） is a popular method for producing MoS2 flakes with different shapes. Here, we report an effective method for achieving a broad range of shape evolution in CVD-grown monolayer MoS2 flakes. By controlling the S and MoO3 temperatures, the shape of the monolayer MoS2 flakes was varied from hexagonal to triangular via intermediate shapes such as truncated and multi-apex triangles. The shape evolution of the MoS2 flakes can be explained by introducing the term “nominal Mo：S ratio”, which refers to the amount of loaded MoO3 and evaporated S powders. By using the nominal Mo：S ratio, we predicted the potential reaction atmosphere and effectively controlled the actual proportion of MoO3-x with respect to S in the growth region, along with the growth temperature. From the systematic investigation of the behavior of the shape evolution, we developed a shape-evolution diagram, which can be used as a practical guide for producing CVD-grown MoS2 flakes with desired shapes展开更多
Efficient algorithms to generate candidate crystal structures with good stability properties can play a key role in data-driven materials discovery.Here,we show that a crystal diffusion variational autoencoder(CDVAE)i...Efficient algorithms to generate candidate crystal structures with good stability properties can play a key role in data-driven materials discovery.Here,we show that a crystal diffusion variational autoencoder(CDVAE)is capable of generating two-dimensional(2D)materials of high chemical and structural diversity and formation energies mirroring the training structures.Specifically,we train the CDVAE on 26152D materials with energy above the convex hullΔH_(hull)<0.3 eV/atom,and generate 5003 materials that we relax using density functional theory(DFT).We also generate 14192 new crystals by systematic element substitution of the training structures.We find that the generative model and lattice decoration approach are complementary and yield materials with similar stability properties but very different crystal structures and chemical compositions.In total we find 11630 predicted new 2D materials,where 8599 of these haveΔH_(hull)<0.3 eV/atom as the seed structures,while 2004 are within 50 meV of the convex hull and could potentially be synthesised.The relaxed atomic structures of all the materials are available in the open Computational 2D Materials Database(C2DB).Our work establishes the CDVAE as an efficient and reliable crystal generation machine,and significantly expands the space of 2D materials.展开更多
We perform a computational screening for two-dimensional(2D)magnetic materials based on experimental bulk compounds present in the Inorganic Crystal Structure Database and Crystallography Open Database.A recently prop...We perform a computational screening for two-dimensional(2D)magnetic materials based on experimental bulk compounds present in the Inorganic Crystal Structure Database and Crystallography Open Database.A recently proposed geometric descriptor is used to extract materials that are exfoliable into 2D derivatives and we find 85 ferromagnetic and 61 antiferromagnetic materials for which we obtain magnetic exchange and anisotropy parameters using density functional theory.For the easy-axis ferromagnetic insulators we calculate the Curie temperature based on a fit to classical Monte Carlo simulations of anisotropic Heisenberg models.We find good agreement with the experimentally reported Curie temperatures of known 2D ferromagnets and identify 10 potentially exfoliable 2D ferromagnets that have not been reported previously.In addition,we find 18 easy-axis antiferromagnetic insulators with several compounds exhibiting very strong exchange coupling and magnetic anisotropy.展开更多
We report a high throughput computational search for two-dimensional ferroelectric materials.The starting point is 252 pyroelectric materials from the computational 2D materials database(C2DB)and from these we identif...We report a high throughput computational search for two-dimensional ferroelectric materials.The starting point is 252 pyroelectric materials from the computational 2D materials database(C2DB)and from these we identify 63 ferroelectrics.In particular we find 49 materials with in-plane polarization,8 materials with out-of-plane polarization and 6 materials with coupled in-plane and out-of-plane polarization.Most of the known 2D ferroelectrics are recovered by the screening and the far majority of the predicted ferroelectrics are known as bulk van der Waals bonded compounds,which makes them accessible by direct exfoliation.For roughly 25%of the materials we find a metastable state in the non-polar structure,which may imply a first order transition to the polar phase.Finally,we list the magnetic pyroelectrics extracted from the C2DB and focus on the case of VAgP2Se6,which exhibits a three-state switchable polarization vector that is strongly coupled to the magnetic excitation spectrum.展开更多
Atomically thin two-dimensional(2D)materials are ideal host systems for quantum defects as they offer easier characterisation,manipulation and read-out of defect states as compared to bulk defects.Here we introduce th...Atomically thin two-dimensional(2D)materials are ideal host systems for quantum defects as they offer easier characterisation,manipulation and read-out of defect states as compared to bulk defects.Here we introduce the Quantum Point Defect(QPOD)database with more than 1900 defect systems comprising various charge states of 503 intrinsic point defects(vacancies and antisites)in 82 different 2D semiconductors and insulators.The Atomic Simulation Recipes(ASR)workflow framework was used to perform density functional theory(DFT)calculations of defect formation energies,charge transition levels,Fermi level positions,equilibrium defect and carrier concentrations,transition dipole moments,hyperfine coupling,and zero-field splitting.Excited states and photoluminescence spectra were calculated for selected high-spin defects.In this paper we describe the calculations and workflow behind the QPOD database,present an overview of its content,and discuss some general trends and correlations in the data.We analyse the degree of defect tolerance as well as intrinsic dopability of the host materials and identify promising defects for quantum technological applications.The database is freely available and can be browsed via a web-app interlinked with the Computational 2D Materials Database(C2DB).展开更多
We address the problem of predicting the zero-temperature dynamical stability (DS) of a periodic crystal without computing its fullphonon band structure. Here we report the evidence that DS can be inferred with good r...We address the problem of predicting the zero-temperature dynamical stability (DS) of a periodic crystal without computing its fullphonon band structure. Here we report the evidence that DS can be inferred with good reliability from the phonon frequencies atthe center and boundary of the Brillouin zone (BZ). This analysis represents a validation of the DS test employed by theComputational 2D Materials Database (C2DB). For 137 dynamically unstable 2D crystals, we displace the atoms along an unstablemode and relax the structure. This procedure yields a dynamically stable crystal in 49 cases. The elementary properties of these newstructures are characterized using the C2DB workflow, and it is found that their properties can differ significantly from those of theoriginal unstable crystals, e.g., band gaps are opened by 0.3 eV on average. All the crystal structures and properties are available inthe C2DB. Finally, we train a classification model on the DS data for 3295 2D materials in the C2DB using a representation encodingthe electronic structure of the crystal. We obtain an excellent receiver operating characteristic (ROC) curve with an area under thecurve (AUC) of 0.90, showing that the classification model can drastically reduce computational efforts in high-throughput studies.展开更多
We analyze a data set comprising 370 GW band structures of two-dimensional(2D)materials covering 14 different crystal structures and 52 chemical elements.The band structures contain a total of 61716 quasiparticle(QP)e...We analyze a data set comprising 370 GW band structures of two-dimensional(2D)materials covering 14 different crystal structures and 52 chemical elements.The band structures contain a total of 61716 quasiparticle(QP)energies obtained from plane-wavebased one-shot G0W0@PBE calculations with full frequency integration.We investigate the distribution of key quantities,like the QP self-energy corrections and QP weights,and explore their dependence on chemical composition and magnetic state.The linear QP approximation is identified as a significant error source and we propose schemes for controlling and drastically reducing this error at low computational cost.We analyze the reliability of the 1/N basis set extrapolation and find that is well-founded with a narrow distribution of coefficients of determination(r^(2))peaked very close to 1.Finally,we explore the accuracy of the scissors operator approximation and conclude that its validity is very limited.Our work represents a step towards the development of automatized workflows for high-throughput G0W0 band structure calculations for solids.展开更多
Exosomes have been recognized as extracellular vesicles that mediate systemic information exchange and long-distance interactions between cells.1 Their functions are all highly reliant on systemic biological distribut...Exosomes have been recognized as extracellular vesicles that mediate systemic information exchange and long-distance interactions between cells.1 Their functions are all highly reliant on systemic biological distribution so that it is possible to promote the biological effects for therapy by accurately manipulating exosome biodistribution.However,given that the mechanisms for regulating the exosome biodistribution are unclear,it is challengeable to achieve the manipulation of exosome biodistribution by regulating molecular signals.Recently,Liu et al.2 reported a vesicle shuttle(VS),which was composed of a ferroferric oxide core,a silica shell,and a stimuli-cleavable poly(ethylene glycol)corona conjugated to two types of antibody(one against antigens on the exosomes of interest,and the other targeted to the recipient injured cells).2 They showed that the VS could effectively collect,transport,and release circulating exosomes to the designated areas inside the organism.展开更多
Graded quantities of 1.38,2.76 and 4.14 g/kg L-methionine were included in a control diet formulated to contain 3.07 g/kg digestible methionine.Each of the 4 dietary treatments was offered to 6 replicate cages(initial...Graded quantities of 1.38,2.76 and 4.14 g/kg L-methionine were included in a control diet formulated to contain 3.07 g/kg digestible methionine.Each of the 4 dietary treatments was offered to 6 replicate cages(initially 8 birds per cage)from 1 to 21 d postehatch.The parameters assessed included growth performance,nutrient utilisation(apparent metabolisable energy[AME],AME:GE ratios,N retention,Ncorrected apparent metabolisable energy[AMEn]),apparent digestibility coefficients and disappearance rates of amino acids in the distal ileum.They also included free amino concentrations in systemic plasma(brachial vein)at 20 d postehatch and in hepatic tissue at 14 and 21 d postehatch.Graded L-methionine inclusions quadratically influenced weight gain(r=0.688;P=0.001)and FCR(r=0.780;P<0.001).It may be deduced from the quadratic regressions that 3.43 g/kg L-methionine supported maximum weight gain of 1,036 g/kg and 3.50 g/kg L-methionine minimum FCR of 1.193,from 1 to 21 d postehatch.The control diet contained specified levels of 3.07 g/kg digestible methionine and 13.0 g/kg digestible lysine.Thus,an inclusion of 3.465 g/kg L-methionine corresponded to a total of 6.535 g/kg methionine or a methionine-to-lysine ratio of 50.3,which is higher than standard recommendations.The implications of this and other outcomes of the present study are reported and discussed.展开更多
Shift current photovoltaic devices are potential candidates for future cheap,sustainable,and efficient electricity generation.In the present work,we calculate the solar-generated shift current and efficiencies in 326 ...Shift current photovoltaic devices are potential candidates for future cheap,sustainable,and efficient electricity generation.In the present work,we calculate the solar-generated shift current and efficiencies in 326 different 2D materials obtained from the computational database C2DB.We apply,as metrics,the efficiencies of monolayer and multilayer samples.The monolayer efficiencies are generally found to be low,while the multilayer efficiencies of infinite stacks show great promise.Furthermore,the out-of-plane shift current response is considered,and material candidates for efficient out-of-plane shift current devices are identified.Among the screened materials,MXY Janus and MX_(2) transition metal dichalchogenides(TMDs)constitute a prominent subset,with chromium based MXY Janus TMDs holding particular promise.Finally,in order to explain the band gap dependence of the PV efficiency,a simple gapped graphene model with a variable band gap is established and related to the calculated efficiencies.展开更多
We report high throughput computational screening for magnetic ground state order in 2D materials.The workflow is based on spin spiral calculations and yields the magnetic order in terms of a twodimensional ordering v...We report high throughput computational screening for magnetic ground state order in 2D materials.The workflow is based on spin spiral calculations and yields the magnetic order in terms of a twodimensional ordering vector Q.We then include spin-orbit coupling to extract the easy and hard axes for collinear structures and the orientation of spiral planes in non-collinear structures.Finally,for all predicted ferromagnetswe compute the Dzyaloshinskii-Moriya interactions and determine whether or not these are strong enough to overcome the magnetic anisotropy and stabilise a chiral spin spiral ground state.We find 58 ferromagnets,21 collinear anti-ferromagnets,and 85 non-collinear ground states of which 15 are chiral spin spirals driven byDzyaloshinskii-Moriya interactions.The results show that non-collinear order is in fact as common as collinear order in these materials and emphasise the need for detailed investigation of the magnetic ground state when reporting magnetic properties of new materials.展开更多
Electronic-structure theory is a strong pillar of materials science.Many different computer codes that employ different approaches are used by the community to solve various scientific problems.Still,the precision of ...Electronic-structure theory is a strong pillar of materials science.Many different computer codes that employ different approaches are used by the community to solve various scientific problems.Still,the precision of different packages has only been scrutinized thoroughly not long ago,focusing on a specific task,namely selecting a popular density functional,and using unusually high,extremely precise numerical settings for investigating 71 monoatomic crystals^(1).Little is known,however,about method- and code-specific uncertainties that arise under numerical settings that are commonly used in practice.We shed light on this issue by investigating the deviations in total and relative energies as a function of computational parameters.Using typical settings for basis sets and k-grids,we compare results for 71 elemental^(1) and 63 binary solids obtained by three different electronic-structure codes that employ fundamentally different strategies.On the basis of the observed trends,we propose a simple,analytical model for the estimation of the errors associated with the basis-set incompleteness.We cross-validate this model using ternary systems obtained from the Novel Materials Discovery (NOMAD) Repository and discuss how our approach enables the comparison of the heterogeneous data present in computational materials databases.展开更多
We review the theory and application of adiabatic exchange–correlation(xc)-kernels for ab initio calculations of ground state energies and quasiparticle excitations within the frameworks of the adiabatic connection f...We review the theory and application of adiabatic exchange–correlation(xc)-kernels for ab initio calculations of ground state energies and quasiparticle excitations within the frameworks of the adiabatic connection fluctuation dissipation theorem and Hedin’s equations,respectively.Various different xc-kernels,which are all rooted in the homogeneous electron gas,are introduced but hereafter we focus on the specific class of renormalized adiabatic kernels,in particular the rALDA and rAPBE.The kernels drastically improve the description of short-range correlations as compared to the random phase approximation(RPA),resulting in significantly better correlation energies.This effect greatly reduces the reliance on error cancellations,which is essential in RPA,and systematically improves covalent bond energies while preserving the good performance of the RPA for dispersive interactions.For quasiparticle energies,the xc-kernels account for vertex corrections that are missing in the GW self-energy.In this context,we show that the short-range correlations mainly correct the absolute band positions while the band gap is less affected in agreement with the known good performance of GW for the latter.The renormalized xc-kernels offer a rigorous extension of the RPA and GW methods with clear improvements in terms of accuracy at little extra computational cost.展开更多
基金approved by the Ethics Committee at the University of Technology Sydney(ETH22-7241)written informed consent(according to the UTS clinical trial declaration)was obtained from all patients before the COVID-19 testing.
文摘The COVID-19 pandemic has underscored the critical need for rapid and accurate diagnostic tools.Current methods,including Polymerase Chain Reaction and rapid antigen tests(RAT),have limitations in speed,sensitivity,and the requirement for specialized equipment and trained personnel.Nanotechnology,particularly upconversion nanoparticles(UCNPs),offer a promising alternative due to their unique optical properties.UCNPs can convert low-energy near-infrared light into higher-energy visible light,making them ideal for use as optical probes in single molecule detection and point of care applications.This study,initiated in early 2020,explores the opportunity of using highly doped UCNPs(40%Yb^(3+)/4%Er^(3+))in lateral flow assay(LFA)for the early diagnosis of COVID-19.The UCNPsbased LFA testing demonstrated a minimum detection concentration of 100 pg/mL for SARS-CoV-2 antigen and 10^(5)CCID_(50)/mL for inactivated virus.Clinical trials,conducted in Malaysia and Western Australia independently,showed that the technique was at least 100 times more sensitive than commercial RAT kits,with a sensitivity of 100%and specificity of 91.94%.The development process involved multidisciplinary collaborations,resulting in the Virulizer device,an automated strip reader for point-of-care testing.This work sets a reference for future development of highly sensitive and quantitative RAT,aiming for the Limits of Detection in the range of sub-ng/mL.
文摘A facile,one-pot,urea solution combustion route was utilized to synthesize highly catalytic CeO2 nanostructures.CeO2 prepared under varying thermal conditions was characterized by electron microscopy,energy dispersive X-ray spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,infrared and Raman techniques.As the synthesis temperature is raised from 400 to 1000℃,the crystallite size and dspacing of nanoparticles are observed to reduce while cell parameters remain in the same range.Particle size exhibits an accession from~20 to~50 nm along the process.Initial CeO2 nanoparticles are detected as a composite structure of CeO2 and graphitic carbon nitride(g-C3 N4)produced by the pyrolysis of urea.Concerning the solid carbon particulate oxidation capacity,an outstanding performance is exhibited by CeO2 synthesized at 800℃where the oxidation onset temperature is reduced by 27%compared with the others.The superior performance is attributed to the carbon nitride-generated unique CeO2 nanomorphology consolidating ample reactive sites and facilitated oxygen delivery for a highly efficient thermocatalytic process.Concerning atmospheric pollution mitigation,synthesis of these CeO2 nanostructures represents a cost effective and convenient abatement technique for carbon particulates in comparison to cost-intensive,environmentally detrimental and noble-metal based techniques.
基金the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation programme Grant No.773122(LIMA)and Grant agreement No.951786(NOMAD CoE)A high-performance computing infrastructure for data-driven research on sustainable energy materials,Grant no.NNF22OC0078009.K.S.T.is a Villum Investigator supported by VILLUM FONDEN(grant no.37789).
文摘We conduct a systematic investigation of the role of Hubbard U corrections in electronic structure calculations of two-dimensional(2D)materials containing 3d transition metals.Specifically,we use density functional theory(DFT)with the PBE and PBE+U approximations to calculate the crystal structure,band gaps,and magnetic parameters of 638 monolayers.Based on a comprehensive comparison to experiments we first establish that the inclusion of the U correction worsens the accuracy for the lattice constants.Consequently,PBE structures are used for subsequent property evaluations.The band gaps show a significant dependence on U.In particular,for 134(21%)of the materials the U parameter induces a metal-to-insulator transition.For the magnetic materials we calculate the magnetic moment,magnetic exchange coupling,and magnetic anisotropy parameters.In contrast to the band gaps,the size of the magnetic moments shows only weak dependence on U.Both the exchange energies and magnetic anisotropy parameters are systematically reduced by theU correction.On this basis we conclude that the Hubbard U correction will lead to lower predicted Curie temperatures in 2D materials.All the calculated properties are available in the Computational 2D Materials Database(C2DB).
基金funded by the VILLUM Center for Science of Sustainable Fuels and Chemicals(VILLUM Fonden research grant 9455)the Novo Nordisk Foundation Data Science Research Infrastructure 2022 Grant(A high-performance computing infrastructure for data-driven research on sustainable energy materials,Grant no.NNF22OC0078009.).The funders played no role in study design,data collection,analysis,interpretation of data,or the writing of this manuscript.
文摘We introduce and discuss a method for global optimization of atomic structures based on the introduction of additional degrees of freedomdescribing:1)the chemical identities of the atoms,2)the degree of existence of the atoms,and 3)their positions in a higher-dimensional space(4-6 dimensions).The new degrees of freedom are incorporated in a machine-learning model through a vectorial fingerprint trained using density functional theory energies and forces.The method is shown to enhance global optimization of atomic structures by circumvention of energy barriers otherwise encountered in the conventional energy landscape.The method is applied to clusters as well as to periodic systems with simultaneous optimization of atomic coordinates and unit cell vectors.Finally,we use the method to determine the possible structures of a dual atomcatalyst consisting of a Fe-Co pair embedded in nitrogen-doped graphene.
文摘In the recent years, transition-metal dichalcogenides such as MoS2 have attracted considerable attention owing to their unique structure and electronic properties. Chemical vapor deposition （CVD） is a popular method for producing MoS2 flakes with different shapes. Here, we report an effective method for achieving a broad range of shape evolution in CVD-grown monolayer MoS2 flakes. By controlling the S and MoO3 temperatures, the shape of the monolayer MoS2 flakes was varied from hexagonal to triangular via intermediate shapes such as truncated and multi-apex triangles. The shape evolution of the MoS2 flakes can be explained by introducing the term “nominal Mo：S ratio”, which refers to the amount of loaded MoO3 and evaporated S powders. By using the nominal Mo：S ratio, we predicted the potential reaction atmosphere and effectively controlled the actual proportion of MoO3-x with respect to S in the growth region, along with the growth temperature. From the systematic investigation of the behavior of the shape evolution, we developed a shape-evolution diagram, which can be used as a practical guide for producing CVD-grown MoS2 flakes with desired shapes
基金We acknowledge funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation programme Grant No.773122(LIMA)Grant agreement No.951786(NOMAD CoE).K.S.T.is a Villum Investigator supported by VILLUM FONDEN(grant no.37789).
文摘Efficient algorithms to generate candidate crystal structures with good stability properties can play a key role in data-driven materials discovery.Here,we show that a crystal diffusion variational autoencoder(CDVAE)is capable of generating two-dimensional(2D)materials of high chemical and structural diversity and formation energies mirroring the training structures.Specifically,we train the CDVAE on 26152D materials with energy above the convex hullΔH_(hull)<0.3 eV/atom,and generate 5003 materials that we relax using density functional theory(DFT).We also generate 14192 new crystals by systematic element substitution of the training structures.We find that the generative model and lattice decoration approach are complementary and yield materials with similar stability properties but very different crystal structures and chemical compositions.In total we find 11630 predicted new 2D materials,where 8599 of these haveΔH_(hull)<0.3 eV/atom as the seed structures,while 2004 are within 50 meV of the convex hull and could potentially be synthesised.The relaxed atomic structures of all the materials are available in the open Computational 2D Materials Database(C2DB).Our work establishes the CDVAE as an efficient and reliable crystal generation machine,and significantly expands the space of 2D materials.
基金D.T.and T.O.were funded by the Danish Independent Research Foundation,Grant number 6108-00464BK.W.J.and H.M.acknowledge support from the VILLUM Center for Science of Sustainable Fuels and Chemicals,which is funded by the VILLUM Fonden research grant 9455.
文摘We perform a computational screening for two-dimensional(2D)magnetic materials based on experimental bulk compounds present in the Inorganic Crystal Structure Database and Crystallography Open Database.A recently proposed geometric descriptor is used to extract materials that are exfoliable into 2D derivatives and we find 85 ferromagnetic and 61 antiferromagnetic materials for which we obtain magnetic exchange and anisotropy parameters using density functional theory.For the easy-axis ferromagnetic insulators we calculate the Curie temperature based on a fit to classical Monte Carlo simulations of anisotropic Heisenberg models.We find good agreement with the experimentally reported Curie temperatures of known 2D ferromagnets and identify 10 potentially exfoliable 2D ferromagnets that have not been reported previously.In addition,we find 18 easy-axis antiferromagnetic insulators with several compounds exhibiting very strong exchange coupling and magnetic anisotropy.
基金M.K.and T.O.were supported by the Danish Independent Research Foundation,Grant number 9040-00269B.U.PT.O.were supported by the Villum foundation,Grant No.00028145.
文摘We report a high throughput computational search for two-dimensional ferroelectric materials.The starting point is 252 pyroelectric materials from the computational 2D materials database(C2DB)and from these we identify 63 ferroelectrics.In particular we find 49 materials with in-plane polarization,8 materials with out-of-plane polarization and 6 materials with coupled in-plane and out-of-plane polarization.Most of the known 2D ferroelectrics are recovered by the screening and the far majority of the predicted ferroelectrics are known as bulk van der Waals bonded compounds,which makes them accessible by direct exfoliation.For roughly 25%of the materials we find a metastable state in the non-polar structure,which may imply a first order transition to the polar phase.Finally,we list the magnetic pyroelectrics extracted from the C2DB and focus on the case of VAgP2Se6,which exhibits a three-state switchable polarization vector that is strongly coupled to the magnetic excitation spectrum.
基金The Center for Nanostructured Graphene (CNG) is sponsored by The Danish National Research Foundation (project DNRF103)We acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program Grant No.773122 (LIMA) and Grant agreement No.951786 (NOMAD CoE)K.S.T.is a Villum Investigator supported by VILLUM FONDEN (grant no.37789).
文摘Atomically thin two-dimensional(2D)materials are ideal host systems for quantum defects as they offer easier characterisation,manipulation and read-out of defect states as compared to bulk defects.Here we introduce the Quantum Point Defect(QPOD)database with more than 1900 defect systems comprising various charge states of 503 intrinsic point defects(vacancies and antisites)in 82 different 2D semiconductors and insulators.The Atomic Simulation Recipes(ASR)workflow framework was used to perform density functional theory(DFT)calculations of defect formation energies,charge transition levels,Fermi level positions,equilibrium defect and carrier concentrations,transition dipole moments,hyperfine coupling,and zero-field splitting.Excited states and photoluminescence spectra were calculated for selected high-spin defects.In this paper we describe the calculations and workflow behind the QPOD database,present an overview of its content,and discuss some general trends and correlations in the data.We analyse the degree of defect tolerance as well as intrinsic dopability of the host materials and identify promising defects for quantum technological applications.The database is freely available and can be browsed via a web-app interlinked with the Computational 2D Materials Database(C2DB).
基金The Center for Nanostructured Graphene(CNG)is sponsored by the Danish National Research Foundation,Project DNRF103This project has received funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program grant agreement no.773122(LIMA)K.S.T.is a Villum Investigator supported by VILLUM FONDEN(grant no.37789).
文摘We address the problem of predicting the zero-temperature dynamical stability (DS) of a periodic crystal without computing its fullphonon band structure. Here we report the evidence that DS can be inferred with good reliability from the phonon frequencies atthe center and boundary of the Brillouin zone (BZ). This analysis represents a validation of the DS test employed by theComputational 2D Materials Database (C2DB). For 137 dynamically unstable 2D crystals, we displace the atoms along an unstablemode and relax the structure. This procedure yields a dynamically stable crystal in 49 cases. The elementary properties of these newstructures are characterized using the C2DB workflow, and it is found that their properties can differ significantly from those of theoriginal unstable crystals, e.g., band gaps are opened by 0.3 eV on average. All the crystal structures and properties are available inthe C2DB. Finally, we train a classification model on the DS data for 3295 2D materials in the C2DB using a representation encodingthe electronic structure of the crystal. We obtain an excellent receiver operating characteristic (ROC) curve with an area under thecurve (AUC) of 0.90, showing that the classification model can drastically reduce computational efforts in high-throughput studies.
基金We acknowledge funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant No.773122,LIMA)The Center for Nanostructured Graphene is sponsored by the Danish National Research Foundation,Project DNRF103+1 种基金This project has received funding in the European Union’s Horizon 2020 research and innovation program under the European Union’s Grant Agreement No.951786(NOMAD CoE)T.D.acknowledges financial support from the German Research Foundation(DFG Project No.DE 2749/2-1).
文摘We analyze a data set comprising 370 GW band structures of two-dimensional(2D)materials covering 14 different crystal structures and 52 chemical elements.The band structures contain a total of 61716 quasiparticle(QP)energies obtained from plane-wavebased one-shot G0W0@PBE calculations with full frequency integration.We investigate the distribution of key quantities,like the QP self-energy corrections and QP weights,and explore their dependence on chemical composition and magnetic state.The linear QP approximation is identified as a significant error source and we propose schemes for controlling and drastically reducing this error at low computational cost.We analyze the reliability of the 1/N basis set extrapolation and find that is well-founded with a narrow distribution of coefficients of determination(r^(2))peaked very close to 1.Finally,we explore the accuracy of the scissors operator approximation and conclude that its validity is very limited.Our work represents a step towards the development of automatized workflows for high-throughput G0W0 band structure calculations for solids.
文摘Exosomes have been recognized as extracellular vesicles that mediate systemic information exchange and long-distance interactions between cells.1 Their functions are all highly reliant on systemic biological distribution so that it is possible to promote the biological effects for therapy by accurately manipulating exosome biodistribution.However,given that the mechanisms for regulating the exosome biodistribution are unclear,it is challengeable to achieve the manipulation of exosome biodistribution by regulating molecular signals.Recently,Liu et al.2 reported a vesicle shuttle(VS),which was composed of a ferroferric oxide core,a silica shell,and a stimuli-cleavable poly(ethylene glycol)corona conjugated to two types of antibody(one against antigens on the exosomes of interest,and the other targeted to the recipient injured cells).2 They showed that the VS could effectively collect,transport,and release circulating exosomes to the designated areas inside the organism.
基金We would like to thank Ms Joy Gill,Ms Kylie Warr,Mr Duwei Chen and Mr Peter Bird of the Peanut Research Foundation within the University of Sydney for their invaluable technical assistance.Also,we would like to acknowledge the financial support provided by Australian Government Research and Training Program International Scholarship(RTP)for the PhD candidature of Mr Shemil Macelline.
文摘Graded quantities of 1.38,2.76 and 4.14 g/kg L-methionine were included in a control diet formulated to contain 3.07 g/kg digestible methionine.Each of the 4 dietary treatments was offered to 6 replicate cages(initially 8 birds per cage)from 1 to 21 d postehatch.The parameters assessed included growth performance,nutrient utilisation(apparent metabolisable energy[AME],AME:GE ratios,N retention,Ncorrected apparent metabolisable energy[AMEn]),apparent digestibility coefficients and disappearance rates of amino acids in the distal ileum.They also included free amino concentrations in systemic plasma(brachial vein)at 20 d postehatch and in hepatic tissue at 14 and 21 d postehatch.Graded L-methionine inclusions quadratically influenced weight gain(r=0.688;P=0.001)and FCR(r=0.780;P<0.001).It may be deduced from the quadratic regressions that 3.43 g/kg L-methionine supported maximum weight gain of 1,036 g/kg and 3.50 g/kg L-methionine minimum FCR of 1.193,from 1 to 21 d postehatch.The control diet contained specified levels of 3.07 g/kg digestible methionine and 13.0 g/kg digestible lysine.Thus,an inclusion of 3.465 g/kg L-methionine corresponded to a total of 6.535 g/kg methionine or a methionine-to-lysine ratio of 50.3,which is higher than standard recommendations.The implications of this and other outcomes of the present study are reported and discussed.
基金M.O.S.,A.T.,K.S.T.,and T.G.P.are supported by the CNG center under the Danish National Research Foundation,project DNRF103U.P.acknowledges funding from the European Union’s Next Generation EU plan through the María Zambrano programme(MAZAM21/19)+2 种基金T.O.is supported by the Villum foundation,Grant No.00028145K.S.T.acknowledge funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program Grant No.773122(LIMA)and Grant agreement No.951786(NOMAD CoE)K.S.T.is a Villum Investigator supported by the Villum foundation(Grant No.37789).
文摘Shift current photovoltaic devices are potential candidates for future cheap,sustainable,and efficient electricity generation.In the present work,we calculate the solar-generated shift current and efficiencies in 326 different 2D materials obtained from the computational database C2DB.We apply,as metrics,the efficiencies of monolayer and multilayer samples.The monolayer efficiencies are generally found to be low,while the multilayer efficiencies of infinite stacks show great promise.Furthermore,the out-of-plane shift current response is considered,and material candidates for efficient out-of-plane shift current devices are identified.Among the screened materials,MXY Janus and MX_(2) transition metal dichalchogenides(TMDs)constitute a prominent subset,with chromium based MXY Janus TMDs holding particular promise.Finally,in order to explain the band gap dependence of the PV efficiency,a simple gapped graphene model with a variable band gap is established and related to the calculated efficiencies.
基金The authors acknowledge support from the Villum foundation Grant No.00029378.
文摘We report high throughput computational screening for magnetic ground state order in 2D materials.The workflow is based on spin spiral calculations and yields the magnetic order in terms of a twodimensional ordering vector Q.We then include spin-orbit coupling to extract the easy and hard axes for collinear structures and the orientation of spiral planes in non-collinear structures.Finally,for all predicted ferromagnetswe compute the Dzyaloshinskii-Moriya interactions and determine whether or not these are strong enough to overcome the magnetic anisotropy and stabilise a chiral spin spiral ground state.We find 58 ferromagnets,21 collinear anti-ferromagnets,and 85 non-collinear ground states of which 15 are chiral spin spirals driven byDzyaloshinskii-Moriya interactions.The results show that non-collinear order is in fact as common as collinear order in these materials and emphasise the need for detailed investigation of the magnetic ground state when reporting magnetic properties of new materials.
基金This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No.676580 and No.740233 (TEC1p)O.T.H.and E.W.gratefully acknowledge funding by the Austrian Science Fund,FWF,under the project P27868-N36.
文摘Electronic-structure theory is a strong pillar of materials science.Many different computer codes that employ different approaches are used by the community to solve various scientific problems.Still,the precision of different packages has only been scrutinized thoroughly not long ago,focusing on a specific task,namely selecting a popular density functional,and using unusually high,extremely precise numerical settings for investigating 71 monoatomic crystals^(1).Little is known,however,about method- and code-specific uncertainties that arise under numerical settings that are commonly used in practice.We shed light on this issue by investigating the deviations in total and relative energies as a function of computational parameters.Using typical settings for basis sets and k-grids,we compare results for 71 elemental^(1) and 63 binary solids obtained by three different electronic-structure codes that employ fundamentally different strategies.On the basis of the observed trends,we propose a simple,analytical model for the estimation of the errors associated with the basis-set incompleteness.We cross-validate this model using ternary systems obtained from the Novel Materials Discovery (NOMAD) Repository and discuss how our approach enables the comparison of the heterogeneous data present in computational materials databases.
基金K.S.T.acknowledges funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(grant agreement No 773122,“LIMA”)The work of A.R.was supported by National Science Foundation under Grant No.DMR-1553022.J.E.B.acknowledges the A.R.Smith Department of Chemistry and Fermentation Sciences for support.
文摘We review the theory and application of adiabatic exchange–correlation(xc)-kernels for ab initio calculations of ground state energies and quasiparticle excitations within the frameworks of the adiabatic connection fluctuation dissipation theorem and Hedin’s equations,respectively.Various different xc-kernels,which are all rooted in the homogeneous electron gas,are introduced but hereafter we focus on the specific class of renormalized adiabatic kernels,in particular the rALDA and rAPBE.The kernels drastically improve the description of short-range correlations as compared to the random phase approximation(RPA),resulting in significantly better correlation energies.This effect greatly reduces the reliance on error cancellations,which is essential in RPA,and systematically improves covalent bond energies while preserving the good performance of the RPA for dispersive interactions.For quasiparticle energies,the xc-kernels account for vertex corrections that are missing in the GW self-energy.In this context,we show that the short-range correlations mainly correct the absolute band positions while the band gap is less affected in agreement with the known good performance of GW for the latter.The renormalized xc-kernels offer a rigorous extension of the RPA and GW methods with clear improvements in terms of accuracy at little extra computational cost.
