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 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
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
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
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 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 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
Weintroduce acomputational framework leveraging universal machine learning interatomic potentials(MLIPs)to dramatically accelerate the calculation of photoluminescence(PL)spectra of atomic or molecular emitters with a...Weintroduce acomputational framework leveraging universal machine learning interatomic potentials(MLIPs)to dramatically accelerate the calculation of photoluminescence(PL)spectra of atomic or molecular emitters with ab initio accuracy.By replacing the costly density functional theory(DFT)computation of phonon modes with much faster MLIP phonon mode calculations,our approach achieves speed improvements exceeding an order of magnitude with minimal precision loss.We benchmark the approach using a dataset comprising ab initio emission spectra of 791 color centers spanning various types of crystal point defects in different charge and magnetic states.The method is also applied to a molecular emitter adsorbed on a hexagonal boron nitride surface.Across all the systems,we find excellent agreement for both the Huang-Rhys factor and the PL lineshapes.This application of universal MLIPs bridges the gap between computational efficiency and spectroscopic fidelity,opening pathways to high-throughput screening of defect-engineered materials.Ourwork not only demonstrates accelerated calculation of PL spectra with DFT accuracy,but also makes such calculations tractable for more complex materials.展开更多
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 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.
基金funding from the Horizon Europe MSCA Doctoral network grant n.101073486, EUSpecLabfunded by the European Union, and from 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+1 种基金F.N. has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 899987K.S.T. is a Villum Investigator supported by VILLUM FONDEN (grant no. 37789).
文摘Weintroduce acomputational framework leveraging universal machine learning interatomic potentials(MLIPs)to dramatically accelerate the calculation of photoluminescence(PL)spectra of atomic or molecular emitters with ab initio accuracy.By replacing the costly density functional theory(DFT)computation of phonon modes with much faster MLIP phonon mode calculations,our approach achieves speed improvements exceeding an order of magnitude with minimal precision loss.We benchmark the approach using a dataset comprising ab initio emission spectra of 791 color centers spanning various types of crystal point defects in different charge and magnetic states.The method is also applied to a molecular emitter adsorbed on a hexagonal boron nitride surface.Across all the systems,we find excellent agreement for both the Huang-Rhys factor and the PL lineshapes.This application of universal MLIPs bridges the gap between computational efficiency and spectroscopic fidelity,opening pathways to high-throughput screening of defect-engineered materials.Ourwork not only demonstrates accelerated calculation of PL spectra with DFT accuracy,but also makes such calculations tractable for more complex materials.
