Heusler compounds attract a great deal of attention from researchers thanks to a wealth of interesting properties,among which is superconductivity.Here we perform an extensive study of the superconducting and elastic ...Heusler compounds attract a great deal of attention from researchers thanks to a wealth of interesting properties,among which is superconductivity.Here we perform an extensive study of the superconducting and elastic properties of the cubic(full-)Heusler family using a mixture of ab initio methods,as well as interpretable and predictive machine-learning models.By analyzing the statistical distributions of these properties and comparing them to anti-perovskites,we recognize universal behaviors that should be common to all conventional superconductors while others turn out to be specific to the material family.In total,we discover a total of eight hypothetical materials with critical temperatures above 10 K to be compared with the current record of T_(c)=4.7 K in this family.Furthermore,we expect most of these materials to be highly ductile,making them potential candidates for the manufacture of wires and tapes for superconducting magnets.展开更多
One of today＇s major challenges is to provide green materials for a cleaner environment. We have conducted studies on carbon dioxide（CO2） adsorption and conversion to valuable products by an ecofriendly approach ba...One of today＇s major challenges is to provide green materials for a cleaner environment. We have conducted studies on carbon dioxide（CO2） adsorption and conversion to valuable products by an ecofriendly approach based in chitosan/graphene oxide（CSGO） nanocomposite film. Rheological behavior indicates that the CSGO has a better solvation property than the pure chitosan. An adsorption capacity of 1.0152 mmol CO2/g of CSGO nanocomposite at4.6 bar was observed. The catalytic behavior of the CSGO nanocomposite in the presence of tetra-n-butylammonium iodide（n-Bu4 NI） as co-catalyst was evaluated for the cycloaddition of CO2 to epoxides, to give cyclic carbonates, in the absence of any solvent. These results strongly suggest that the CSGO nanocomposite may open new vistas towards the development of ecofriendly material for catalytic conversion and adsorption of CO2 on industrial scale.展开更多
The incorporation of interface passivation structures in ultrathin Cu(In,Ga)Se_(2)based solar cells is shown.The fabrication used an industry scalable lithography technique—nanoimprint lithography(NIL)—for a 15×...The incorporation of interface passivation structures in ultrathin Cu(In,Ga)Se_(2)based solar cells is shown.The fabrication used an industry scalable lithography technique—nanoimprint lithography(NIL)—for a 15×15 cm^(2)dielectric layer patterning.Devices with a NIL nanopatterned dielectric layer are benchmarked against electron-beam lithography(EBL)patterning,using rigid substrates.The NIL patterned device shows similar performance to the EBL patterned device.The impact of the lithographic processes in the rigid solar cells’performance were evaluated via X-ray Photoelectron Spectroscopy and through a Solar Cell Capacitance Simulator.The device on stainless-steel showed a slightly lower performance than the rigid approach,due to additional challenges of processing steel substrates,even though scanning transmission electron microscopy did not show clear evidence of impurity diffusion.Notwithstanding,time-resolved photoluminescence results strongly suggested elemental diffusion from the flexible substrate.Nevertheless,bending tests on the stainless-steel device demonstrated the mechanical stability of the CIGS-based device.展开更多
We present a comprehensive theoretical study of conventional superconductivity in cubic antiperovskites materials with composition XYZ_(3) where X and Z are metals,and Y is H,B,C,N,O,and P.Our starting point are elect...We present a comprehensive theoretical study of conventional superconductivity in cubic antiperovskites materials with composition XYZ_(3) where X and Z are metals,and Y is H,B,C,N,O,and P.Our starting point are electron–phonon calculations for 397 materials performed with density-functional perturbation theory.While 43%of the materials are dynamically unstable,we discovered 16 compounds close to thermodynamic stability and with T_(c) higher than 5 K.Using these results to train interpretable machine-learning models,leads us to predict a further 57(thermodynamically unstable)materials with superconducting transition temperatures above 5 K,reaching a maximum of 17.8 K for PtHBe3.Furthermore,the models give us an understanding of the mechanism of superconductivity in antiperovskites.The combination of traditional approaches with interpretable machine learning turns out to be a very efficient methodology to study and systematize whole classes of materials and is easily extendable to other families of compounds or physical properties.展开更多
The chemical preparation, crystal structure and infrared spectroscopic characterization of the triaqua（4-amino-6-methoxypyrimidine） cuprate（II） sulfate, [Cu（C5H7N3）（H2O）3]SO4, is reported. The compound crystal...The chemical preparation, crystal structure and infrared spectroscopic characterization of the triaqua（4-amino-6-methoxypyrimidine） cuprate（II） sulfate, [Cu（C5H7N3）（H2O）3]SO4, is reported. The compound crystallizes in the noncentrosymmetric orthorhombic space group P212121 with lattice parameters a = 7.9025（3）, b = 11.1189（4）, c = 12.9720（4） , V = 1139.81（7） ~3 and Z = 4. The Cu（II） cation is fivecoordinated, in an early half-way between square pyramidal and trigonal bipyramidal fashion, by two nitrogen atoms of the 4-amino-6-methoxypyrimidine ligand and three water oxygen atoms. In the atomic arrangement, the organic ligands and the 5-connected Cu centers are linked with each other to give a 1-D corrugated hybrid chain running along the b-axis direction. The chains are interconnected by the SO4^（2-） anions via O–H...O, O–H...S, C–H...O and N–H...O hydrogen bonds to form layers spreading parallel to the（011） plane. The vibrational absorption bands were identified by infrared spectroscopy. Quantitative measurements of the second harmonic generation（SHG） of a powdered sample at 1064 nm were performed and a relative efficiency of 5.2 times the KDP standard was observed. Magnetic properties were also defined to characterize the complex. Magnetic measurements revealed that this material had a onedimensional antiferromagnetic character. The magnetic parameters were g = 2.11 and 2J/k B = -36 K.展开更多
In this work,we present a large-scale study of gap deformation potentials based on density-functional theory calculations for over 5000 semiconductors.As expected,in most cases the band gap decreases for increasing vo...In this work,we present a large-scale study of gap deformation potentials based on density-functional theory calculations for over 5000 semiconductors.As expected,in most cases the band gap decreases for increasing volume with deformation potentials that can reach values of almost−15 eV.We find,however,also a sizeable number of materials with positive deformation potentials.Notorious members of this group are halide perovskites,known for their applications in photovoltaics.We then focus on understanding the physical reasons for so different values of the deformation potentials by investigating the correlations between this property and a large number of other material and compositional properties.We also train explainable machine learning models as well as graph convolutional networks to predict deformation potentials and establish simple rules to understand predicted values.Finally,we analyze in more detail a series of materials that have record positive and negative deformation potentials.展开更多
In this paper,we report on the crystal structure and magnetic properties of the nano structured Baordered phases of rare-earth manganites obtained from the optimally doped solid solutions Ln0.70Ba0.30MnO3(Ln=Pr,Nd).Th...In this paper,we report on the crystal structure and magnetic properties of the nano structured Baordered phases of rare-earth manganites obtained from the optimally doped solid solutions Ln0.70Ba0.30MnO3(Ln=Pr,Nd).The materials were studied by X-ray diffraction,scanning electron microscopy,energy dispersive spectroscopy and SQUID-magnetometry techniques.It is found that states with different degrees of cation ordering in the A-sublattice of the ABO3 perovskite can be obtained by employing special conditions of chemical treatment.In particular,reduction of the parent compounds results in the formation of a nanocomposite containing ferrimagnetic anion-deficient ordered phase LnBaMn2O5.Oxidation of the composite does not change an average size of the nanocrystallites,but drastically alters their phase composition to stabilize ferromagnetic stoichiometric ordered phase LnBaMn2O6 and ferromagnetic superstoichiometric disordered phase Ln0.90Ba0.10MnO3+δ.It is shown that the magnetic properties of the materials are determined by the joint action of chemical(cation ordering)and external(surface tension)pressures.展开更多
Light and heavy clusters are calculated for warm stellar matter in the framework of relativistic mean-field models, in the single-nucleus approximation. The cluster abundances are determined from the minimization of t...Light and heavy clusters are calculated for warm stellar matter in the framework of relativistic mean-field models, in the single-nucleus approximation. The cluster abundances are determined from the minimization of the free energy. In-medium effects of light cluster properties are included by introducing an explicit binding energy shift analytically calculated in the Thomas–Fermi approximation, and the coupling constants are fixed by imposing that the virial limit at low density is recovered. The resulting light cluster abundances come out to be in reasonable agreement with constraints at higher density coming from heavy-ion collision data. Some comparisons with microscopic calculations are also shown.展开更多
Phytochemical investigations of the ethanolic extract of leaves of Clutia lanceolata(Family:Euphorbiaceae)resulted in the isolation of four compounds viz.3,4-dihydroxy-2-methylbenzoic acid(1),2,20-dihydroxy-1,10-binap...Phytochemical investigations of the ethanolic extract of leaves of Clutia lanceolata(Family:Euphorbiaceae)resulted in the isolation of four compounds viz.3,4-dihydroxy-2-methylbenzoic acid(1),2,20-dihydroxy-1,10-binaphthyl(2),1,3,8-trihydroxy-6-methylanthracene-9,10-dione(3)and 5-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)hepta-1,4,6-trien-3-one(4).Although all the isolated compounds were known but this was the first report from this plant source.Their structures were established on the basis of chemical and physical evidences viz.elemental analysis,FT-IR,1 H-NMR,13CNMR and mass spectral analysis.Structure of compound 2 and 4 was further authenticated by single-crystal X-ray analysis and density functional theory calculations.The isolated compounds(1–4)were screened for AChE enzyme inhibition assay in which compound 3 and 4 were found to be more potent AChE inhibitor.Molecular docking study of potent AChE inhibitor was performed to find the probable binding mode of the compounds into the active site of receptor.Moreover,the isolated compounds were also screened for in vivo cytotoxicity by brine shrimp lethality assay.展开更多
基金T.F.T.C.and P.B.acknowledge financial support from Fundação para a Ciência e Tecnologia(FCT),Portugal(projects UIDB/04564/2020 and 2022.09975.PTDC and contract 2020.04225.CEECIND)the Laboratory for Advanced Computing at University of Coimbra for providing HPC resources that have contributed to the research results reported within this paper.
文摘Heusler compounds attract a great deal of attention from researchers thanks to a wealth of interesting properties,among which is superconductivity.Here we perform an extensive study of the superconducting and elastic properties of the cubic(full-)Heusler family using a mixture of ab initio methods,as well as interpretable and predictive machine-learning models.By analyzing the statistical distributions of these properties and comparing them to anti-perovskites,we recognize universal behaviors that should be common to all conventional superconductors while others turn out to be specific to the material family.In total,we discover a total of eight hypothetical materials with critical temperatures above 10 K to be compared with the current record of T_(c)=4.7 K in this family.Furthermore,we expect most of these materials to be highly ductile,making them potential candidates for the manufacture of wires and tapes for superconducting magnets.
基金supported by the KU Brain Pool 2017 of Konkuk University,Seoul,South KoreaFundacao para a Ciência e a Tecnologia(FCT),Portugal(SFRH/BPD/86507/2012)Centro de Quimica de Coimbra(CQC),University of Coimbra for their support
文摘One of today＇s major challenges is to provide green materials for a cleaner environment. We have conducted studies on carbon dioxide（CO2） adsorption and conversion to valuable products by an ecofriendly approach based in chitosan/graphene oxide（CSGO） nanocomposite film. Rheological behavior indicates that the CSGO has a better solvation property than the pure chitosan. An adsorption capacity of 1.0152 mmol CO2/g of CSGO nanocomposite at4.6 bar was observed. The catalytic behavior of the CSGO nanocomposite in the presence of tetra-n-butylammonium iodide（n-Bu4 NI） as co-catalyst was evaluated for the cycloaddition of CO2 to epoxides, to give cyclic carbonates, in the absence of any solvent. These results strongly suggest that the CSGO nanocomposite may open new vistas towards the development of ecofriendly material for catalytic conversion and adsorption of CO2 on industrial scale.
基金InovSolarCells(PTDC/FISMAC/29696/2017)co-funded by FCT and the ERDF through COMPETE2020And by the European Union’s Horizon 2020 research and innovation programme under the grants agreements N°.720887(ARCIGS-M project)+2 种基金grand agreement N°.715027(Uniting PV)P.M.P.S.and P.A.F.would like to acknowledge FCT for the support of the project FCT UIDB/04730/2020This work was developed within the scope of the project i3N,UIDB/50025/2020&UIDP/50025/2020,financed by national funds through the FCT/MEC.
文摘The incorporation of interface passivation structures in ultrathin Cu(In,Ga)Se_(2)based solar cells is shown.The fabrication used an industry scalable lithography technique—nanoimprint lithography(NIL)—for a 15×15 cm^(2)dielectric layer patterning.Devices with a NIL nanopatterned dielectric layer are benchmarked against electron-beam lithography(EBL)patterning,using rigid substrates.The NIL patterned device shows similar performance to the EBL patterned device.The impact of the lithographic processes in the rigid solar cells’performance were evaluated via X-ray Photoelectron Spectroscopy and through a Solar Cell Capacitance Simulator.The device on stainless-steel showed a slightly lower performance than the rigid approach,due to additional challenges of processing steel substrates,even though scanning transmission electron microscopy did not show clear evidence of impurity diffusion.Notwithstanding,time-resolved photoluminescence results strongly suggested elemental diffusion from the flexible substrate.Nevertheless,bending tests on the stainless-steel device demonstrated the mechanical stability of the CIGS-based device.
基金T.F.T.C.acknowledges the financial support from the CFisUC through the project UIDB/04564/2020 and the Laboratory for Advanced Computing at the University of Coimbra for providing HPC resources that have contributed to the research results reported within this paper.
文摘We present a comprehensive theoretical study of conventional superconductivity in cubic antiperovskites materials with composition XYZ_(3) where X and Z are metals,and Y is H,B,C,N,O,and P.Our starting point are electron–phonon calculations for 397 materials performed with density-functional perturbation theory.While 43%of the materials are dynamically unstable,we discovered 16 compounds close to thermodynamic stability and with T_(c) higher than 5 K.Using these results to train interpretable machine-learning models,leads us to predict a further 57(thermodynamically unstable)materials with superconducting transition temperatures above 5 K,reaching a maximum of 17.8 K for PtHBe3.Furthermore,the models give us an understanding of the mechanism of superconductivity in antiperovskites.The combination of traditional approaches with interpretable machine learning turns out to be a very efficient methodology to study and systematize whole classes of materials and is easily extendable to other families of compounds or physical properties.
基金support provided by the Secretary of State for Scientific Research and Technology of TunisiaThe X-ray diffractometer was funded by NSF Grant 0087210, Ohio Board of Regents Grant CAP-491 and by Youngstown State University, USA
文摘The chemical preparation, crystal structure and infrared spectroscopic characterization of the triaqua（4-amino-6-methoxypyrimidine） cuprate（II） sulfate, [Cu（C5H7N3）（H2O）3]SO4, is reported. The compound crystallizes in the noncentrosymmetric orthorhombic space group P212121 with lattice parameters a = 7.9025（3）, b = 11.1189（4）, c = 12.9720（4） , V = 1139.81（7） ~3 and Z = 4. The Cu（II） cation is fivecoordinated, in an early half-way between square pyramidal and trigonal bipyramidal fashion, by two nitrogen atoms of the 4-amino-6-methoxypyrimidine ligand and three water oxygen atoms. In the atomic arrangement, the organic ligands and the 5-connected Cu centers are linked with each other to give a 1-D corrugated hybrid chain running along the b-axis direction. The chains are interconnected by the SO4^（2-） anions via O–H...O, O–H...S, C–H...O and N–H...O hydrogen bonds to form layers spreading parallel to the（011） plane. The vibrational absorption bands were identified by infrared spectroscopy. Quantitative measurements of the second harmonic generation（SHG） of a powdered sample at 1064 nm were performed and a relative efficiency of 5.2 times the KDP standard was observed. Magnetic properties were also defined to characterize the complex. Magnetic measurements revealed that this material had a onedimensional antiferromagnetic character. The magnetic parameters were g = 2.11 and 2J/k B = -36 K.
基金S.B.acknowledges the financial support from the Volkswagen Stiftung(Momentum)through the project“dandelion”P.B.acknowledges the financial support from the CFisUC through the project UIDB/04564/2020 and FCT under the contract 2020.04225.CEECIND.
文摘In this work,we present a large-scale study of gap deformation potentials based on density-functional theory calculations for over 5000 semiconductors.As expected,in most cases the band gap decreases for increasing volume with deformation potentials that can reach values of almost−15 eV.We find,however,also a sizeable number of materials with positive deformation potentials.Notorious members of this group are halide perovskites,known for their applications in photovoltaics.We then focus on understanding the physical reasons for so different values of the deformation potentials by investigating the correlations between this property and a large number of other material and compositional properties.We also train explainable machine learning models as well as graph convolutional networks to predict deformation potentials and establish simple rules to understand predicted values.Finally,we analyze in more detail a series of materials that have record positive and negative deformation potentials.
基金Project supported by the European Union’s Horizon 2020Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement(778070)
文摘In this paper,we report on the crystal structure and magnetic properties of the nano structured Baordered phases of rare-earth manganites obtained from the optimally doped solid solutions Ln0.70Ba0.30MnO3(Ln=Pr,Nd).The materials were studied by X-ray diffraction,scanning electron microscopy,energy dispersive spectroscopy and SQUID-magnetometry techniques.It is found that states with different degrees of cation ordering in the A-sublattice of the ABO3 perovskite can be obtained by employing special conditions of chemical treatment.In particular,reduction of the parent compounds results in the formation of a nanocomposite containing ferrimagnetic anion-deficient ordered phase LnBaMn2O5.Oxidation of the composite does not change an average size of the nanocrystallites,but drastically alters their phase composition to stabilize ferromagnetic stoichiometric ordered phase LnBaMn2O6 and ferromagnetic superstoichiometric disordered phase Ln0.90Ba0.10MnO3+δ.It is shown that the magnetic properties of the materials are determined by the joint action of chemical(cation ordering)and external(surface tension)pressures.
基金partly supported by the FCT(Portugal)Project No.UID/FIS/04564/2016by former NewCompStar,COST Action MP1304.H.P.is supported by FCT(Portugal)under Project No.SFRH/BPD/95566/2013the Organizers of IWND 2018 for the opportunity to present this work,as well as the financial support received
文摘Light and heavy clusters are calculated for warm stellar matter in the framework of relativistic mean-field models, in the single-nucleus approximation. The cluster abundances are determined from the minimization of the free energy. In-medium effects of light cluster properties are included by introducing an explicit binding energy shift analytically calculated in the Thomas–Fermi approximation, and the coupling constants are fixed by imposing that the virial limit at low density is recovered. The resulting light cluster abundances come out to be in reasonable agreement with constraints at higher density coming from heavy-ion collision data. Some comparisons with microscopic calculations are also shown.
文摘Phytochemical investigations of the ethanolic extract of leaves of Clutia lanceolata(Family:Euphorbiaceae)resulted in the isolation of four compounds viz.3,4-dihydroxy-2-methylbenzoic acid(1),2,20-dihydroxy-1,10-binaphthyl(2),1,3,8-trihydroxy-6-methylanthracene-9,10-dione(3)and 5-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)hepta-1,4,6-trien-3-one(4).Although all the isolated compounds were known but this was the first report from this plant source.Their structures were established on the basis of chemical and physical evidences viz.elemental analysis,FT-IR,1 H-NMR,13CNMR and mass spectral analysis.Structure of compound 2 and 4 was further authenticated by single-crystal X-ray analysis and density functional theory calculations.The isolated compounds(1–4)were screened for AChE enzyme inhibition assay in which compound 3 and 4 were found to be more potent AChE inhibitor.Molecular docking study of potent AChE inhibitor was performed to find the probable binding mode of the compounds into the active site of receptor.Moreover,the isolated compounds were also screened for in vivo cytotoxicity by brine shrimp lethality assay.
