Superionic and electride behaviors in materials,which induce a variety of exotic physical properties of ions and electrons,are of great importance both in fundamental research and for practical applications.However,th...Superionic and electride behaviors in materials,which induce a variety of exotic physical properties of ions and electrons,are of great importance both in fundamental research and for practical applications.However,their coexistence in hot alkali-metal borides has not been observed.In this work,we apply first-principles structure search calculations to identify eight Na-B compounds with host-vip structures,which exhibit a wide range of building blocks and interesting properties linked to the Na/B composition.Among the known borides,Na-rich Na9B stands out as the composition with the highest alkali-metal content,featuring vertex-and face-sharing BNa16 polyhedra.Notably,it exhibits electride characteristics and transforms into a superionic electride at 200 GPa and 2000 K,displaying unusual Na atomic diffusion behavior attributed to the modulation of the interstitial anion electrons.It demonstrates semiconductor behavior in the solid state,and metallic properties associated with Na 3p/3s states in the superionic and liquid regions.On the other hand,B-rich NaB7,consisting of a unique covalent B framework,is predicted to exhibit low-frequency phonon-mediated superconductivity with a T_(c) of 16.8 K at 55 GPa.Our work advances the understanding of the structures and properties of alkali-metal borides.展开更多
Since the discovery of hydride superconductors,a significant challenge has been to reduce the pressure required for their stabilization.In this context,we propose that alloying could be an effective strategy to achiev...Since the discovery of hydride superconductors,a significant challenge has been to reduce the pressure required for their stabilization.In this context,we propose that alloying could be an effective strategy to achieve this.We focus on a series of alloyed hydrides with the AMH_(6)composition,which can be made via alloying A15 AH_(3)(A=Al or Ga)with M(M=a group IIIB or IVB metal),and study their behavior under pressure.Seven of them are predicted to maintain the A15-type structure,similar to AH_(3)under pressure,providing a platform for studying the effects of alloying on the stability and superconductivity of AH_(3).Among these,the A15-type phases of AlZrH_(6)and AlHfH_(6)are found to be thermodynamically stable in the pressure ranges of 40–150 and 30–181 GPa,respectively.Furthermore,they remain dynamically stable at even lower pressures,as low as 13 GPa for AlZrH_(6)and 6 GPa for AlHfH_(6).These pressures are significantly lower than that required for stabilizing A15 AlH3.Additionally,the introduction of Zr or Hf increases the electronic density of states at the Fermi level compared with AlH3.This enhancement leads to higher critical temperatures(Tc)of 75 and 76 K for AlZrH_(6)and AlHfH_(6)at 20 and 10 GPa,respectively.In the case of GaMH_(6)alloys,where M represents Sc,Ti,Zr,or Hf,these metals reinforce the stability of the A15-type structure and reduce the lowest thermodynamically stable pressure for GaH_(3) from 160 GPa to 116,95,80,and 85 GPa,respectively.Particularly noteworthy are the A15-type GaMH_(6)alloys,which remain dynamically stable at low pressures of 97,28,5,and 6 GPa,simultaneously exhibiting high Tc of 88,39,70,and 49 K at 100,35,10,and 10 GPa,respectively.Overall,these findings enrich the family of A15-type superconductors and provide insights for the future exploration of high-temperature hydride superconductors that can be stabilized at lower pressures.展开更多
Electrides,materials in which a portion of valence electrons reside as interstitial anionic electrons(IAEs)within lattice cavities-exhibit a wide range of extraordinary physical and chemical properties,making them a c...Electrides,materials in which a portion of valence electrons reside as interstitial anionic electrons(IAEs)within lattice cavities-exhibit a wide range of extraordinary physical and chemical properties,making them a central focus of condensed matter physics.Under high pressure,intermetallic systems provide a unique pathway to novel electrides by enabling unconventional charge-transfer mechanisms.Here,we employ first-principles structure searches to identify two stable Li-Mg electrides,Li_(3)Mg and Li_(4)Mg.At low pressure,Mg atoms act as anionic centers through occupation of their outer-shell 3p orbitals.Upon compression,charge is transferred from Mg to the lattice cavities,enhancing the localization and density of IAEs.This,in turn,strengths electron-phonon coupling and raises the superconducting transition temperature(T_(c))to 13.3 K at 75 GPa for Li_(3)Mg and 19.7 K at 80 GPa for Li_(4)Mg-values that surpass most known electride superconductors below 100 GPa.Selective hydrogen insertion into the lattice cavities in Li_(4)Mg quenches the IAEs and confirms their essential role in superconductivity.Further compression drives a transition to poor or non-superconducting phases,with Mg atoms switching from electron acceptors to donors,contrary to the typical behavior of electropositive metals,which tend to transition from donors into acceptors under pressure.These findings highlight the pivotal role of IAEs in electride superconductivity and pave the way for designing novel intermetallic electrides with tunable properties.展开更多
Extended hydrogen-rich frameworks stabilized under high pressure are essential for achieving high-temperature superconductivity in metal hydrides,where metal atoms contribute both charge and intrinsic precompression.I...Extended hydrogen-rich frameworks stabilized under high pressure are essential for achieving high-temperature superconductivity in metal hydrides,where metal atoms contribute both charge and intrinsic precompression.In contrast,p-block nonmetal hydrides lack such extended hydrogenic connectivity.Here,using first-principles crystal structure search calculations,we identify three nitrogen-based superhydrides-NH_(10),NH_(11),and NH_(12)-each featuring a unique extended H sublattice:corrugated graphene-like hydrogen layers in NH_(10),planar H_(16)-ring sheets in NH11,and a fully three-dimensional,densely connected H framework in NH12.These structures are stabilized by NH_(4)^(+)units,which donate charge in a manner analogous to metal atoms in conventional metal superhydrides.Remarkably,NH_(10)exhibits a superconducting critical temperature(T_(c))of 190 K at 200 GPa,driven by strong electron-phonon coupling between H-1s states and low-frequency hydrogen-derived phonon modes-a mechanism notably distinct from that of hydrogen cages in LaH_(10)and CaH_(6).The predicted T_(c)values of NH_(11)and NH_(12)also exceeds 130 K.Our work introduces a new paradigm for designing nonmetal superhydrides with structurally engineered hydrogenic frameworks.展开更多
Boron and its compounds have attracted much attention due to their interesting and complex structures[1-4].In particular,boron-rich compounds containing icosahedral structures have excellent properties,such as low den...Boron and its compounds have attracted much attention due to their interesting and complex structures[1-4].In particular,boron-rich compounds containing icosahedral structures have excellent properties,such as low density,high hardness,high melting point and low wear coffi-cient.展开更多
基金This work was supported by the Natural Science Foundation of China under Grant No.21573037the Postdoctoral Science Foundation of China under Grant No.2013M541283+4 种基金the Natural Science Foundation of Hebei Province(Grant No.B2021203030)the Science and Technology Project of Hebei Education Department(Grant Nos.JZX2023020 and QN2023246)A.B.acknowledges financial support from the Spanish Ministry of Science and Innovation(Grant No.PID2019-105488GB-I00)the Department of Education,Universities and Research of the Basque Government and the University of the Basque Country(Grant No.IT1707-22)This work was carried out at the National Supercomputer Center in Tianjin,and the calculations were performed on TianHe-1(A).
文摘Superionic and electride behaviors in materials,which induce a variety of exotic physical properties of ions and electrons,are of great importance both in fundamental research and for practical applications.However,their coexistence in hot alkali-metal borides has not been observed.In this work,we apply first-principles structure search calculations to identify eight Na-B compounds with host-vip structures,which exhibit a wide range of building blocks and interesting properties linked to the Na/B composition.Among the known borides,Na-rich Na9B stands out as the composition with the highest alkali-metal content,featuring vertex-and face-sharing BNa16 polyhedra.Notably,it exhibits electride characteristics and transforms into a superionic electride at 200 GPa and 2000 K,displaying unusual Na atomic diffusion behavior attributed to the modulation of the interstitial anion electrons.It demonstrates semiconductor behavior in the solid state,and metallic properties associated with Na 3p/3s states in the superionic and liquid regions.On the other hand,B-rich NaB7,consisting of a unique covalent B framework,is predicted to exhibit low-frequency phonon-mediated superconductivity with a T_(c) of 16.8 K at 55 GPa.Our work advances the understanding of the structures and properties of alkali-metal borides.
基金supported by the Natural Science Foundation of China(Grant Nos.52022089,52372261,52288102,and 11964026)the National Key R&D Program of China(Grant No.2022YFA1402300)+5 种基金the Natural Science Foundation of Hebei Province(Grant No.E2022203109)the Doctoral Fund of Henan University of Technology(Grant No.31401579)P.L.thanks the Science and Technology Leading Talents and Innovation Team Building Projects of the Inner Mongolia Autonomous Region(Grant No.GXKY22060)financial support from the Spanish Ministry of Science and Innovation(Grant No.FIS2019-105488GB-I00)the Department of Education,Universities and Research of the Basque Government and the University of the Basque Country(Grant No.IT1707-22)the National Science Foundation(Grant No.DMR-2136038)for financial support.
文摘Since the discovery of hydride superconductors,a significant challenge has been to reduce the pressure required for their stabilization.In this context,we propose that alloying could be an effective strategy to achieve this.We focus on a series of alloyed hydrides with the AMH_(6)composition,which can be made via alloying A15 AH_(3)(A=Al or Ga)with M(M=a group IIIB or IVB metal),and study their behavior under pressure.Seven of them are predicted to maintain the A15-type structure,similar to AH_(3)under pressure,providing a platform for studying the effects of alloying on the stability and superconductivity of AH_(3).Among these,the A15-type phases of AlZrH_(6)and AlHfH_(6)are found to be thermodynamically stable in the pressure ranges of 40–150 and 30–181 GPa,respectively.Furthermore,they remain dynamically stable at even lower pressures,as low as 13 GPa for AlZrH_(6)and 6 GPa for AlHfH_(6).These pressures are significantly lower than that required for stabilizing A15 AlH3.Additionally,the introduction of Zr or Hf increases the electronic density of states at the Fermi level compared with AlH3.This enhancement leads to higher critical temperatures(Tc)of 75 and 76 K for AlZrH_(6)and AlHfH_(6)at 20 and 10 GPa,respectively.In the case of GaMH_(6)alloys,where M represents Sc,Ti,Zr,or Hf,these metals reinforce the stability of the A15-type structure and reduce the lowest thermodynamically stable pressure for GaH_(3) from 160 GPa to 116,95,80,and 85 GPa,respectively.Particularly noteworthy are the A15-type GaMH_(6)alloys,which remain dynamically stable at low pressures of 97,28,5,and 6 GPa,simultaneously exhibiting high Tc of 88,39,70,and 49 K at 100,35,10,and 10 GPa,respectively.Overall,these findings enrich the family of A15-type superconductors and provide insights for the future exploration of high-temperature hydride superconductors that can be stabilized at lower pressures.
基金supported by the Natural Science Foundation of China under Grants No.22372142,12304028,and 12404027the Foreign Expert Introduction Program(G2023003004L)+6 种基金the Central Guiding Local Science and Technology Development Fund Projects(236Z7605G)the Natural Science Foundation of Hebei Province(Grant No.B2024203051,A2024203023,and A2024203002)the Science and Technology Project of Hebei Education Department(Grants No.JZX2023020)Innovation Capability Improvement Project of Hebei province(22567605H)Hebei Province Yan Zhao Huang Jin Tai Talent Program(Postdoctoral Platform,B2024003003)support from the Spanish Ministry of Science and Innovation(Grant No.PID2022-139230NB-I00)the Department of Education,Universities and Research of the Basque Government and the University of the Basque Country(Grant No.IT1707-22).
文摘Electrides,materials in which a portion of valence electrons reside as interstitial anionic electrons(IAEs)within lattice cavities-exhibit a wide range of extraordinary physical and chemical properties,making them a central focus of condensed matter physics.Under high pressure,intermetallic systems provide a unique pathway to novel electrides by enabling unconventional charge-transfer mechanisms.Here,we employ first-principles structure searches to identify two stable Li-Mg electrides,Li_(3)Mg and Li_(4)Mg.At low pressure,Mg atoms act as anionic centers through occupation of their outer-shell 3p orbitals.Upon compression,charge is transferred from Mg to the lattice cavities,enhancing the localization and density of IAEs.This,in turn,strengths electron-phonon coupling and raises the superconducting transition temperature(T_(c))to 13.3 K at 75 GPa for Li_(3)Mg and 19.7 K at 80 GPa for Li_(4)Mg-values that surpass most known electride superconductors below 100 GPa.Selective hydrogen insertion into the lattice cavities in Li_(4)Mg quenches the IAEs and confirms their essential role in superconductivity.Further compression drives a transition to poor or non-superconducting phases,with Mg atoms switching from electron acceptors to donors,contrary to the typical behavior of electropositive metals,which tend to transition from donors into acceptors under pressure.These findings highlight the pivotal role of IAEs in electride superconductivity and pave the way for designing novel intermetallic electrides with tunable properties.
基金supported by the Natural Science Foundation of China(grant nos.22372142,12304028,and 12404027)Foreign Ex-pert Introduction Program,China(G2023003004L)+6 种基金Central Guiding Local Science and Technology Development Fund Projects,China(236Z7605G)Natural Science Foundation of Hebei Province,China(grant nos.B2024203051,A2024203023,and A2024203002)Science and Technology Project of Hebei Education Department,China(grant no.JZX2023020)Innovation Capability Improvement Project of Hebei province,China(22567605H)Hebei Province Yan Zhao Huang Jin Tai Talent Program,China(Postdoctoral Platform,B2024003003)A.B.acknowledges financial support from the Spanish Ministry of Science and Innovation,Spain(Grant No.PID2022-139230NB-I00)the Department of Education,Universities and Research of the Basque Government,Spain and the University of the Basque Country,Spain(Grant No.IT1707-22).
文摘Extended hydrogen-rich frameworks stabilized under high pressure are essential for achieving high-temperature superconductivity in metal hydrides,where metal atoms contribute both charge and intrinsic precompression.In contrast,p-block nonmetal hydrides lack such extended hydrogenic connectivity.Here,using first-principles crystal structure search calculations,we identify three nitrogen-based superhydrides-NH_(10),NH_(11),and NH_(12)-each featuring a unique extended H sublattice:corrugated graphene-like hydrogen layers in NH_(10),planar H_(16)-ring sheets in NH11,and a fully three-dimensional,densely connected H framework in NH12.These structures are stabilized by NH_(4)^(+)units,which donate charge in a manner analogous to metal atoms in conventional metal superhydrides.Remarkably,NH_(10)exhibits a superconducting critical temperature(T_(c))of 190 K at 200 GPa,driven by strong electron-phonon coupling between H-1s states and low-frequency hydrogen-derived phonon modes-a mechanism notably distinct from that of hydrogen cages in LaH_(10)and CaH_(6).The predicted T_(c)values of NH_(11)and NH_(12)also exceeds 130 K.Our work introduces a new paradigm for designing nonmetal superhydrides with structurally engineered hydrogenic frameworks.
基金supported by the Fostering Program of Major Research Plan of the National Natural Science Foundation of China(91963115)the National Key R&D Program of China(2018YFA0703400)+3 种基金the National Natural Science Foundation of China(51732010)the Ph D Foundation by Yanshan University(B970)financial support from the Spanish Ministry of Economy and Competitiveness(FIS2016-76617-P)the Department of Education,Universities,Research of the Basque Government and the University of the Basque Country(IT756-13)。
文摘Boron and its compounds have attracted much attention due to their interesting and complex structures[1-4].In particular,boron-rich compounds containing icosahedral structures have excellent properties,such as low density,high hardness,high melting point and low wear coffi-cient.
