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Two-dimensional ferroelectrics from high throughput computational screening

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npj Computational Materials 2023年第1期9卷 1901-1911页

作者： Mads Kruse Urko Petralanda Morten N.Gjerding Karsten W.Jacobsen kristian s.thygesen Thomas Olsen CAMD Department of PhysicsTechnical University of DenmarkDK-2800 Kongens LyngbyDenmark

We report a high throughput computational search for two-dimensional ferroelectric *** starting point is 252 pyroelectric materials from the computational 2D materials database(C2DB)and from these we identify 63 *** 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 *** 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 *** 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 ***,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.

关键词： materials polarization plane

Exploring and machine learning structural instabilities in 2D materials

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npj Computational Materials 2023年第1期9卷 2016-2025页

作者： simone Manti Mark Kamper svendsen Nikolaj R.Knøsgaard Peder M.Lyngby kristian s.thygesen CAMD Computational Atomic-Scale Materials DesignDepartment of PhysicsTechnical University of Denmark2800 Kgs.LyngbyDenmark Center for Nanostructured Graphene(CNG) Department of PhysicsTechnical University of DenmarkDK-2800 Kongens LyngbyDenmark

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.

关键词： structure unstable structural

Beyond the RPA and GW methods with adiabatic xc-kernels for accurate ground state and quasiparticle energies

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npj Computational Materials 2019年第1期5卷 202-224页

作者： Thomas Olsen Christopher E.Patrick Jefferson E.Bates Adrienn Ruzsinszky kristian s.thygesen Computational Atomic-scale Materials Design(CAMD) Department of PhysicsTechnical University of DenmarkKongens LyngbyDenmark Department of Physics University of WarwickCoventry CV47ALUK A.R.smith Department of Chemistry and Fermentation sciences Appalachian State UniversityBooneNC 28607USA Department of Physics Temple UniversityPhiladelphiaPA 19122USA Center for Nanostructured Graphene(CNG) Department of PhysicsTechnical University of DenmarkKongens LyngbyDenmark

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,*** 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 *** kernels drastically improve the description of short-range correlations as compared to the random phase approximation(RPA),resulting in significantly better correlation *** 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 *** quasiparticle energies,the xc-kernels account for vertex corrections that are missing in the GW *** 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 *** 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.

关键词： adiabatic kernels quasi

structural and chemical mechanisms governing stability of inorganic Janus nanotubes

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npj Computational Materials 2021年第1期7卷 380-387页

作者： Felix T.Bölle August E.G.Mikkelsen kristian s.thygesen Tejs Vegge Ivano E.Castelli Department of Energy Conversion and storage Technical University of DenmarkKgs.LyngbyDenmark Department of Physics Technical University of DenmarkKgs.LyngbyDenmark

One-dimensional inorganic nanotubes hold promise for technological applications due to their distinct physical/chemical properties,but so far advancements have been hampered by difficulties in producing single-wall nanotubes with a well-defined *** this work we investigate,based on Density Functional Theory(DFT),the formation mechanism of 135 different inorganic nanotubes formed by the intrinsic self-rolling driving force found in asymmetric 2D Janus *** show that for isovalent Janus sheets,the lattice mismatch between inner and outer atomic layers is the driving force behind the nanotube formation,while in the non-isovalent case it is governed by the difference in chemical bond strength of the inner and outer layer leading to steric *** our pool of candidate structures we have identified more than 100 tubes with a preferred radius below 35Å,which we hypothesize can display distinctive properties compared to their parent 2D *** descriptors have been identified to accelerate the discovery of small-radius tubes and a Bayesian regression approach has been implemented to assess the uncertainty in our predictions on the radius.

关键词： inorganic chemical radius

Data-driven discovery of 2D materials by deep generative models

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npj Computational Materials 2022年第1期8卷 2218-2225页

作者： Peder Lyngby kristian sommer thygesen Computational Atomic-scale Materials Design(CAMD) Department of PhysicsTechnical University of Denmark2800Kgs.LyngbyDenmark

Efficient algorithms to generate candidate crystal structures with good stability properties can play a key role in data-driven materials ***,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 ***,we train the CDVAE on 26152D materials with energy above the convex hullΔH_(hull)s that we relax using density functional theory(DFT).We also generate 14192 new crystals by systematic element substitution of the training *** 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 *** total we find 11630 predicted new 2D materials,where 8599 of these haveΔH_(hull)s the seed structures,while 2004 are within 50 meV of the convex hull and could potentially be *** 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.

关键词： crystal convex stability

shift current photovoltaic efficiency of 2D materials

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npj Computational Materials 2023年第1期9卷 1991-1999页

作者： Mikkel Ohm sauer Alireza Taghizadeh Urko Petralanda Martin Ovesen kristian sommer thygesen Thomas Olsen Horia Cornean Thomas Garm Pedersen Department of Materials and Production Aalborg University9220 AalborgØstDenmark Department of Mathematical sciences Aalborg University9220 AalborgØstDenmark Center for Nanostructured Graphene(CNG) 9220 AalborgØstDenmark Computational Atomic-scale Materials Design(CAMD) Department of PhysicsTechnical University of Denmark2800 Kgs.LyngbyDenmark Department of Physics University of the Basque Country(UPV/EHU)Apartado 644Bilbao 48080Spain Center for Nanostructured Graphene(CNG) 2800 Kgs.LyngbyDenmark

shift current photovoltaic devices are potential candidates for future cheap,sustainable,and efficient electricity *** the present work,we calculate the solar-generated shift current and efficiencies in 326 different 2D materials obtained from the computational database *** apply,as metrics,the efficiencies of monolayer and multilayer *** monolayer efficiencies are generally found to be low,while the multilayer efficiencies of infinite stacks show great ***,the out-of-plane shift current response is considered,and material candidates for efficient out-of-plane shift current devices are *** the screened materials,MXY Janus and MX_(2) transition metal dichalchogenides(TMDs)constitute a prominent subset,with chromium based MXY Janus TMDs holding particular ***,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.

关键词： shift database multilayer

Inocula selection in microbial fuel cells based on anodic biofilm abundance of Geobacter sulfurreducens

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Chinese Journal of Chemical Engineering 2016年第3期24卷 379-387页

作者： Guotao sun Diogo de sacadura Rodrigues Anders.thygesen Geoffrey Daniel Dinesh Fernando Anne s.Meyer Center for BioProcess Engineering Department of Chemical and Biochemical EngineeringTechnical University of Denmark Department of Forest Products Swedish University of Agricultural Sciences

Microbial fuel cells （MFCs） rely on microbial conversion of organic substrates to electricity. The optimal perfor- mance depends on the establishment of a microbial community rich in electrogenic bacteria. Usually this micro- bial community is established from inoculation of the MFC anode chamber with naturally occurring mixed inocula. In this study, the electrochemical performance of MFCs and microbial community evolution were eval- uated for three inocula including domestic wastewater （DW）, lake sediment （Ls） and biogas sludge （Bs） with varying substrate loading （Lsub） and external resistance （Rext） on the MFC. The electrogenic bacterium Geobacter sulfurreducens was identified in all inocula and its abundance during MFC operation was positively linked to the MFC performance. The Is inoculated MFCs showed highest abundance （18% ± 1%） of G. sulfurreducens, maximum current density [Imax = （690 ± 30） mA.m 2] and coulombic efficiency （CE = 29% ±1%） with acetate as the substrate./max and CE increased to （1780 ± 30） mA.m-2 and 58%± 1%, respectively, after decreasing the Rext from 1000 Ωto 200 Ω, which also correlated to a higher abundance ofG. sulfurreducens （21% ±0.7%） on the MFC anodic biofilm. The data obtained contribute to understanding the microbial community response to Lsub and Roy, for of timizing electricity eneration in MFCs.

关键词： Lake sediment Coulombic efficiency Denaturing gradient gel electrophoresis Geobacter sulfurreducens Anode polarisation resistance

Numerical quality control for DFT-based materials databases

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npj Computational Materials 2022年第1期8卷 661-668页

作者： Christian Carbogno kristian sommer thygesen Björn Bieniek Claudia Draxl Luca M.Ghiringhelli Andris Gulans Oliver T.Hofmann Karsten W.Jacobsen sven Lubeck Jens Jørgen Mortensen Mikkel strange Elisabeth Wruss Matthias scheffler Fritz-Haber-Institut der Max-Planck-Gesellschaft Faradayweg 4-614195BerlinGermany Center for Atomic-scale Materials Design(CAMD) Department of PhysicsTechnical University of DenmarkFysikvej 12800Kongens LyngbyDenmark Physics Department and IRIs Adlershof Humboldt-Universität zu BerlinZum Großen Windkanal 612489BerlinGermany Institute of solid state Physics Graz University of TechnologyNAWI GrazPetergasse 168010GrazAustria

Electronic-structure theory is a strong pillar of materials *** different computer codes that employ different approaches are used by the community to solve various scientific ***,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 *** shed light on this issue by investigating the deviations in total and relative energies as a function of computational *** 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 *** the basis of the observed trends,we propose a simple,analytical model for the estimation of the errors associated with the basis-set *** 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.

关键词： structure precise selecting

Change in Preoperative Nervousness: A Randomized Controlled Trial in Gynecological Cancer Patients

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Health 2016年第3期8卷 219-229页

作者： Marianne K. thygesen René De Pont Christensen Lone Hedemand Ole Mogensen Institute of Clinical Research Faculty of Health Sciences University of Southern Denmark Odense Denmark Department of Obstetrics and Gynaecology Odense University Hospital Odense Denmark Research Unit of General Practice University of Southern Denmark Odense Denmark

Patients are often nervous prior to surgery and females might suffer the most. Increased nervousness needs attention as it can negatively affect postoperative recovery. support from nurses, i.e. being present, attentive, empowering and helpful to the patient, and talking about what is on the patient’s mind, might help to reduce nervousness. However, there is a lack of evidence as to the ideal level of attention and resources to reduce preoperative nervousness. The objective of the current study was to compare a range of care combinations with standard care to female patients prior to sedation and cancer surgery primarily on difference in change in nervousness from admission until sedation before cancer surgery, measured on a Visual Analouge scale. Using simple randomization and numbers in sealed envelopes, adult gynaecological patients scheduled for open cancer surgery were allocated to care provided by a nurse anaesthetist and: A) a surgical nurse, B) no additional care, C) a known nurse , and D) a relative. Only the statistician was blinded. The trial stopped when the calculated numbers were included. In the full analysis set, compared to standard care A) (n = 61), we observed the following mean changes and [95% confidence intervals]: B) (n = 65) 1.05 [CI: 0.298 to 1.794] with p = 0.006, C) (n = 61): -0.38 [-1.140 to 0.385] with p = 0.330, D) (n = 71): 0.23 [-0.498 to 0.967] with p = 0.528. Female cancer patients will benefit from supportive care by a surgical nurse from the time of arrival on the operating ward plus supportive care from a nurse anesthetist from 5 - 10 minutes after entering the operating ward. It is not recommended at any time to rely fully on the support of relatives. The effect on adults of preoperative painful procedures and patients’ time alone on the operating ward should be further investigated.

关键词： Anxiety Cancer Perioperative Care Randomized Controlled Trial Women’s Health