Achieving room-temperature superconductivity has been an enduring scientific quest,while hydrogen-rich compounds have emerged as highly promising candidates.Here,we systematically investigated the thermodynamic stabil...Achieving room-temperature superconductivity has been an enduring scientific quest,while hydrogen-rich compounds have emerged as highly promising candidates.Here,we systematically investigated the thermodynamic stability,crystal structure,electronic properties,and superconductivity within the ternary Y-Hf-H system under high pressure.Several distinct hydrides have been revealed,in which the hydrogen atoms are present in various hydrogenic motifs.A15-type hydride P_(m)3-YHfH_(6)with isolated H−is predicted to be dynamically stabilized down to 10GPa.The H atoms form pentagonal graphene-like layered-H10 anions in the Hf plane of P6-YHfH_(19),with aT_(c)of 95K at 100GPa.There are H cages in C_(mmm)-Y_(3)HfH_(24),and attributed to the robust electron–phonon coupling and high electronic density of states of hydrogen at the Fermi level,it demonstrates near-room temperature superconductivity with a T_(c)of 275K at 250GPa.Our work makes contributions to the understanding of the fundamental properties of ternary hydrides under high pressure and provides essential references for further research in this field.展开更多
The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the re...The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the realization of superconductivity in compressively strained La_(3)Ni_(2)O_(7)thin films grown on the SrLaAlO_(4)substrates,with a T_(c)exceeding 40 K,represents a significant step toward this goal.Here,we investigate the influence of film thickness and carrier doping on the electronic structure of La_(3)Ni_(2)O_(7)thin films,ranging from 0.5 to 3 unit cells,using first-principles calculations.For a 2 unit-cell film with an optimal doping concentration of 0.3 hole per formula unit(0.15 hole/Ni),the Ni-d_(z^(2))interlayer bonding state crosses the Fermi level,resulting in the formation ofγpockets at the Fermi surface.These findings align with angle-resolved photoemission spectroscopy experimental data.Our results provide theoretical validation for the recent experimental discovery of ambient-pressure superconductivity in La_(3)Ni_(2)O_(7)thin films and underscore the significant impact of film thickness and carrier doping on electronic property modulation.展开更多
The high-pressure phase diagram of the Nb-Ti binary system at 0 K is explored by systematic crystal structure prediction.The results highlight a novel niobium-rich bcc phase,Nb_(7)Ti,which is the only dynamically stab...The high-pressure phase diagram of the Nb-Ti binary system at 0 K is explored by systematic crystal structure prediction.The results highlight a novel niobium-rich bcc phase,Nb_(7)Ti,which is the only dynamically stable ordered Nb-Ti compound under ambient pressure.Extensive first-principles calculations have provided insights into the electronic structure,bonding and superconducting properties of Nb_(7)Ti.The superconducting transition temperature(T_(c))for Nb_(7)Ti at ambient pressure is estimated within the framework of BCS theory to be about 17.5 K,which is significantly higher—nearly double—that of the widely utilized NbTi alloy.Furthermore,the results unveil that the high T_(c) is mainly attributed to the unique ordered lattice along with the strong electron-phonon coupling driven by interatomic interactions at mid-frequency and phonon softening induced by low-frequency Fermi surface nesting.Valuable insights are provided for the subsequent synthesis of application-oriented superconductors at low pressure.展开更多
Two-dimensional(2D)superconductors have attracted significant research interest due to their promising potential applications in optoelectronic and microelectronic devices.Herein,we employ first-principles calculation...Two-dimensional(2D)superconductors have attracted significant research interest due to their promising potential applications in optoelectronic and microelectronic devices.Herein,we employ first-principles calculations to predicted a new 2D conventional superconductor,Tc_(2)B_(2),demonstrating its stable structural configuration.Remarkably,under biaxial strain,the superconducting transition temperature(T_(c))of Tc_(2)B_(2)demonstrates a significant enhancement,achieving 19.5 K under 3%compressive strain and 9.2 K under 11%tensile strain.Our study reveals that strain-induced modifications in Fermi surface topology significantly enhance the Fermi surface nesting effect,which amplifies electron–phonon coupling interactions and consequently elevates Tc.Additionally,the presence of the Lifshitz transition results in a more pronounced rise in Tc under compressive strain compared to tensile strain.These insights offer important theoretical guidance for designing 2D superconductors with high-Tc through strain modulation.展开更多
Perovskites have garnered significant attention in recent years. However, the presence of La atoms at the B-site in ABX_(3) structures has not yet been observed. Under high pressure, perovskites exhibit unexpected pha...Perovskites have garnered significant attention in recent years. However, the presence of La atoms at the B-site in ABX_(3) structures has not yet been observed. Under high pressure, perovskites exhibit unexpected phase transitions. In this study, we report the discovery of SbLaO_(3) under ambient pressure, with a space group of R3m. Mechanical property calculations indicate that it is a brittle material, and it possesses a band gap of 4.0266 e V, classifying it as an insulator.We also investigate the phase at 300 GPa, where the space group shifts to P2_(1/m). Additionally, the P2_(1/m) phase of LaInO_(3) under 300 GPa is explored. Ab initio molecular dynamics calculations reveal that the melting point of SbLaO_(3) is exceptionally high. The inclusion of Sb alters the electronic structure compared with LaInO_(3), and the Vickers hardness(H_(v)) is estimated to reach 20.97 GPa. This research provides insights into the phase transitions of perovskites under high pressure.展开更多
Using first-principles evolutionary crystal structure prediction,we systematically investigate scandium polychlorides across 50-300 GPa,predicting multiple thermodynamically stable phases ScCl,ScCl_(2),ScCl_(3),ScCl_(...Using first-principles evolutionary crystal structure prediction,we systematically investigate scandium polychlorides across 50-300 GPa,predicting multiple thermodynamically stable phases ScCl,ScCl_(2),ScCl_(3),ScCl_(5),and ScCl_(7)with unconventional stoichiometries.The exceptional stability of these compounds stems from the mutually compatible crystal orbitals of the Sc and Cl sublattices,strong ionic interactions,and the formation of Cl-Cl homobonds.These factors play critical roles in stabilizing scandium chloride compounds with various unconventional stoichiometries.Notably highpressure novel ScCl phases with P63/mmc and Pm-3m symmetries can be metastable at ambient pressure upon decompression and convert into superconductive electrides.Pm-3-ScCl_(7)exhibits significant pressure-modulated superconductivity,featuring an enhancement of T_(c)to 10.91 K at a low pressure of 75 GPa.In addition,the universal superconductivity found in the Pm-3 structured chlorides suggests a promising structural prototype for pressure-tunable superconductors.展开更多
Recently,a breakthrough in the high-pressure synthesis of sp^(3)-bonded clathrate-like R-3m-L_(a)B_(8)featuring Latrapped B_(26)cages was achieved.Although the superconducting critical temperature(T_(c))and Vickers ha...Recently,a breakthrough in the high-pressure synthesis of sp^(3)-bonded clathrate-like R-3m-L_(a)B_(8)featuring Latrapped B_(26)cages was achieved.Although the superconducting critical temperature(T_(c))and Vickers hardness(H_(v))of L_(a)B_(8)were estimated,the anisotropic superconductivity and superconducting gap nature remain unclear.The stability of pure B_(26)cages under ambient conditions is of interest for exploring the B_(26)hardness and the role of La atoms in the L_(a)B_(8)hardness.By resolving the Allen–Dynes modified Mc Millan equation and the anisotropic Eliashberg equations,it was found that L_(a)B_(8)exhibits anisotropic single-gap superconductivity with T_(c)=19.0~26.5 K,and the superconducting gap anisotropic ratio reaches 48.50%at 5 K.Most significantly,our work fundamentally validated the coupling of B-2p orbitals with the optical double-degenerate E_(g)phonon modes and A_(g)phonon mode from a novel perspective.The H_(v)of B_(26)cages was determined to be 18.6 GPa,which is lower than that of La-trapped B_(26)cages(i.e.,L_(a)B_(8)),indicating that La acts as a hardness enhancer for L_(a)B_(8).展开更多
Element superconductors with the single atoms provide clean and fundamental platforms for studying superconductivity.Although elements with d electrons are usually not favored by conventional BCS,the record supercondu...Element superconductors with the single atoms provide clean and fundamental platforms for studying superconductivity.Although elements with d electrons are usually not favored by conventional BCS,the record superconducting critical temperature(T_(c))in element scandium(S_(c))has further ignited the intensive attention on transition metals.The element molybdenum(M_o)with a half-full d-orbital is studied in our work,which fills the gap in the study of Mo under high pressure and investigates the pressure dependence of superconductivity.In this work,we exhibit a robust superconductivity of Mo in the pressure range of 5 GPa to 160 GPa via high-pressure electrical transport measurements,the T_(c) varies at a rate of0.013 K/GPa to 8.56 K at 160 GPa.Moreover,the superconductivity is evidenced by the T_(c) shifting to lower temperature under applied magnetic fields,and the upper critical magnetic fields are extrapolated by the WHH equation and GL equation;the results indicate that the maximum upper critical magnetic field is estimated to be 8.24 T at 137 GPa.We further investigate the superconducting mechanism of Mo,the theoretical calculations indicate that the superconductivity can be attributed to the strong coupling between the electrons from the partially filled d band and the phonons from the frequency zone of 200-400 cm^(-1).展开更多
Two-dimensional(2D)materials have demonstrated promising prospects owing to their distinctive electronic properties and exceptional mechanical properties.Among them,2D superconductors with T_(c) above the boiling poin...Two-dimensional(2D)materials have demonstrated promising prospects owing to their distinctive electronic properties and exceptional mechanical properties.Among them,2D superconductors with T_(c) above the boiling point of liquid nitrogen(77 K)will exhibit tremendous applicable value in the future.Here,we design two 2D superconductors Na(BC)_(2) and K(BC)_(2) with MgB2-like structures,which are theoretically predicted to host T_(c) as high as 99 and 102 K,respectively.The origin of such high T_(c) is ascribed to the presence of both𝜎-bonding bands and van Hove singularity at the Fermi level.Furthermore,T_(c) of Na(BC)_(2) is boosted up to 153K with a biaxial strain of 5%,which sets a new record among 2D superconductors.The predictions of Na(BC)_(2) and K(BC)_(2) open the door to explore 2D high-temperature superconductors and provide a potential future for developing new applications in 2D materials.展开更多
Sulfur and lanthanum hydrides under compression display superconducting states with high observed critical temperatures.It has been recently demonstrated that carbonaceous sulfur hydride displays room temperature supe...Sulfur and lanthanum hydrides under compression display superconducting states with high observed critical temperatures.It has been recently demonstrated that carbonaceous sulfur hydride displays room temperature superconductivity.However,this phenomenon has been observed only at very high pressure.Here,we theoretically search for superconductors with very high critical temperatures,but at much lower pressures.We describe two of such sodalite-type clathrate hydrides,YbH6 and LuH6.These hydrides are metastable and are predicted to superconduct with T_(c)~145 K at 70 GPa and T_(c)~273 K at 100 GPa,respectively.This striking result is a consequence of the strong interrelationship between the f states present at the Fermi level,structural stability,and the final T_(c) value.For example,TmH6,with unfilled 4f orbitals,is stable at 50 GPa,but has a relatively low value of T_(c) of 25 K.The YbH6 and LuH6 compounds,with their filled f-shells,exhibit prominent phonon"softening",which leads to a strong electron-phonon coupling,and as a result,an increase in T_(c).展开更多
Recently,room-temperature superconductivity has been reported in a nitrogen-doped lutetium hydride at near-ambient pressure[Dasenbrock-Gammon et al.,Nature 615,244(2023)].The superconducting properties might arise fro...Recently,room-temperature superconductivity has been reported in a nitrogen-doped lutetium hydride at near-ambient pressure[Dasenbrock-Gammon et al.,Nature 615,244(2023)].The superconducting properties might arise from Fm3m-LuH_(3)−δNε.Here,we systematically study the phase diagram of Lu–N–H at 1 GPa using first-principles calculations,and we do not find any thermodynamically stable ternary compounds.In addition,we calculate the dynamic stability and superconducting properties of N-doped Fm3m-LuH_(3) using the virtual crystal approximation(VCA)and the supercell method.The R3m-Lu_(2)H_(5)N predicted using the supercell method could be dynamically stable at 50 GPa,with a T_(c) of 27 K.According to the VCA method,the highest T_(c) is 22 K,obtained with 1%N-doping at 30 GPa.Moreover,the doping of nitrogen atoms into Fm3m-LuH_(3) slightly enhances T_(c),but raises the dynamically stable pressure.Our theoretical results show that the T_(c) values of N-doped LuH_(3) estimated using the Allen–Dynes-modified McMillan equation are much lower than room temperature.展开更多
On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorab...On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorable mechanical properties using boron-rich compounds.In this paper,first-principles calculations reveal the existence of an unprecedented family of tetragonal pentaborides MB_(5)(M=Na,K,Rb,Ca,Sr,Ba,Sc,and Y),comprising B_(20)cages and centered metal atoms acting as stabilizers and electron donors to the boron sublattice.These compounds exhibit both superconductivity and high hardness,with the maximum superconducting transition temperature T_(c)of 18.6 K being achieved in RbB5 and the peak Vickers hardness Hv of 35.1 GPa being achieved in KB_(5)at 1 atm.The combination of these properties is particularly evident in KB_(5),RbB5,and BaB5,with Tc values of∼14.7,18.6,and 16.3 K and H_(v)values of∼35.1,32.4,and 33.8 GPa,respectively.The results presented here reveal that pentaborides can provide a framework for exploring and designing novel superconducting materials with favorable hardness at achievable pressures and even under ambient conditions.展开更多
First-principles evolutionary calculation was performed to search for all probable stable Ga–Te compounds at extreme pressure. In addition to the well-known structures of P6_3/mmc and Fm-3 m Ga Te and I4/m Ga_2 Te_5,...First-principles evolutionary calculation was performed to search for all probable stable Ga–Te compounds at extreme pressure. In addition to the well-known structures of P6_3/mmc and Fm-3 m Ga Te and I4/m Ga_2 Te_5, several new structures were uncovered at high pressure, namely, orthorhombic I4/mmm GaTe_2 and monoclinic C2/m Ga Te_3, and all the Ga–Te structures stabilize up to a maximum pressure of 80 GPa. The calculation of the electronic energy band indicated that the high-pressure phases of the Ga–Te system are metallic, whereas the low-pressure phases are semiconductors. The electronic localization functions(ELFs) of the Ga–Te system were also calculated to explore the bond characteristics. The results showed that a covalent bond is formed at low pressure, however, this bond disappears at high pressure, and an ionic bond is formed at extreme pressure.展开更多
Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literatur...Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literature.The energy difference of C2vand C3vstructures is qualitatively affected by the supercell size,and the 216-atom supercell could be proposed as the minimum to obtain stable configuration of substitutional S in diamond.Using supercells of up to 512 atoms,the donor level of substitutional S with C2vsymmetry is deep.展开更多
The variational and diffusion Monte Carlo approaches are used to study the ground-state properties of a hydrogen molecular ion in a spheroidal box. In this work, we successfully treat the zero-point motion of protons ...The variational and diffusion Monte Carlo approaches are used to study the ground-state properties of a hydrogen molecular ion in a spheroidal box. In this work, we successfully treat the zero-point motion of protons in the same formalism with as of electrons and avoid the Born–Oppenheimer approximation in density function theory. The study shows that the total energy increases with the decrease in volume, and that the distance between protons decreases as the pressure increases.Considering the motion of protons, the kinetic energy of the electron is higher than that of the fixed model under the same conditions and increases by 5%. The kinetic energy of the proton is found to be small under high pressure, which is only a fraction of the kinetic energy of the electron.展开更多
Pressure has an important effect on chemical bonds and their chemical properties. The atypical compounds NaCl_(3) and CsF_(3) are predicted to be stable at high pressure and show unique physical and chemical propertie...Pressure has an important effect on chemical bonds and their chemical properties. The atypical compounds NaCl_(3) and CsF_(3) are predicted to be stable at high pressure and show unique physical and chemical properties. By using ab initio random structure searching and density functional theory calculations, we predicted multiple thermodynamically stable atypical compounds, which are RbF_(2), RbF_(3), RbF_(4), and RbF_(5) in the pressure range of 0–300 GPa. In these stable compounds, homonuclear bondings of F_(3), F_(4), and F_(5) species are easily formed. The electron structure calculation showed that except for Fd-3 m phase of RbF_(2), these stable compounds are insulators and F 5 p orbitals play an important role in the Fermi level. It is interesting that the compounds RbF_(5) could be stable at nearly ambient pressure and 0 K which will stimulate experimental studies in the future.展开更多
We conduct extensive research into the structures of Be_(x)Zn_(1-x)OO ternary alloys in a pressure range of 0-60GPa,using the ab initio total energy evolutionary algorithm and total energy calculations,finding several...We conduct extensive research into the structures of Be_(x)Zn_(1-x)OO ternary alloys in a pressure range of 0-60GPa,using the ab initio total energy evolutionary algorithm and total energy calculations,finding several metastable structures.Our pressure-composition phase diagram is constructed using the enthalpy results.In addition,we calculate the electronic structures of the Be_(x)Zn_(1-x)OO structures and investigate the bandgap values at varying pressures and Be content.The calculated results show that the bandgap of the Be_(x)Zn_(1-x)OO ternary alloys increases with an increase in Be content at the same pressure.Moreover,the bandgap of the Be_(x)Zn_(1-x)OO ternary alloys increases with the increasing pressure with fixed Be content.At the same Be content,the formation enthalpy of the Be_(x)Zn_(1-x)OO ternary alloys first decreases,then increases with the increasing pressure.展开更多
Ammonium iodine(NH4I)as an important member of hydrogen-rich compounds has attracted a great deal of attention owing to its interesting structural changes triggered by the relative orientations of adjacent ammonium io...Ammonium iodine(NH4I)as an important member of hydrogen-rich compounds has attracted a great deal of attention owing to its interesting structural changes triggered by the relative orientations of adjacent ammonium ions.Previous studies of ammonium iodide have remained in the low pressure range experimentally,which we first extended to so high pressure(250 GPa).We have investigated the structures of ammonium iodine under high pressure through ab initio evolutionary algorithm and total energy calculations based on density functional theory.The static enthalpy calculations show that phase V is stable until 85 GPa where a new phase Ibam is identified.Calculations of phonon spectra show that the Ibam phase is stable between 85 GPa and 101 GPa and the Cm phase is stable up to 130 GPa.In addition,ammonium iodine dissociates into NH3,H2,and I2 at 74 GPa.Subsequently,we analyzed phonon spectra and electronic band structures,finding that phonon softening is not the reason of dissociation and NH4I is always a semiconductor within the pressure range.展开更多
Trilayer Ruddlesden-Popper phase La_(4)Ni_(3)O_(10) has been observed with T_(c) of~30 K at high pressure in a recent experiment,which further expanded the family of nickelate superconductors.In this study,we explored...Trilayer Ruddlesden-Popper phase La_(4)Ni_(3)O_(10) has been observed with T_(c) of~30 K at high pressure in a recent experiment,which further expanded the family of nickelate superconductors.In this study,we explored the effects of electronic correlations in La_(4)Ni_(3)O_(10) using density functional theory plus dynamical mean-field theory at ambient and high pressures.Our derived spectral functions and Fermi surface of the ambient pressure phase are nicely consistent with the experimental results by angleresolved photoemission spectroscopy,which emphasized the importance of electronic correlations in La_(4)Ni_(3)O_(10).We also found the electronic correlations in pressurized La_(4)Ni_(3)O_(10) are both orbital-dependent and layer-dependent due to the presence of Hund’s rule coupling.There is a competition between the Hund’s rule coupling and the crystal-field splitting,and therefore,the Ni-O layers with weaker crystal-field splitting energy would have stronger electronic correlations.展开更多
The recent transport measurements of La_(3)Ni_(2)O_(7)uncovered a“right-triangle”shape of the superconducting dome in the pressure-temperature(P-T)phase diagram.Motivated by this,we perform theoretical first-princip...The recent transport measurements of La_(3)Ni_(2)O_(7)uncovered a“right-triangle”shape of the superconducting dome in the pressure-temperature(P-T)phase diagram.Motivated by this,we perform theoretical first-principles studies of La_(3)Ni_(2)O_(7)with the pressure ranging from 0 to 100 GPa.Notably,we reveal a pressure dependence of the Ni-d_(z^(2))electron density at the Fermi energy(n_(z)^(E_(F)))that highly coincides with such shape.On this basis,we further explore the electronic structure under uniaxial stress.By tracking the stress response of n_(z)^(E_(F)),we propose that superconductivity can be achieved by applying only ~2GPa of compression along the c axis.The idea is further exemplified from the perspectives of lattice distortion,band structure,Fermi surface and superconducting phase coherence.We also discuss the possible charge modulation under the stress and provide an insight into the relation between nz E Fand the superconducting T_(c)in La_(3)Ni_(2)O_(7)system.Our study provides new routes to the search of high-T_(c)superconductors in future experiments.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52072188,12122405,and 12274169)Program for Science and Technology Innovation Team in Zhejiang Province,China(Grant No.2021R01004)+2 种基金Natural Science Foundation of Zhejiang Province,China(Grant No.LQ24A040001)the Natural Science Foundation of Ningbo City,China(Grant No.2024J200)the Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.SJLY2023003)。
文摘Achieving room-temperature superconductivity has been an enduring scientific quest,while hydrogen-rich compounds have emerged as highly promising candidates.Here,we systematically investigated the thermodynamic stability,crystal structure,electronic properties,and superconductivity within the ternary Y-Hf-H system under high pressure.Several distinct hydrides have been revealed,in which the hydrogen atoms are present in various hydrogenic motifs.A15-type hydride P_(m)3-YHfH_(6)with isolated H−is predicted to be dynamically stabilized down to 10GPa.The H atoms form pentagonal graphene-like layered-H10 anions in the Hf plane of P6-YHfH_(19),with aT_(c)of 95K at 100GPa.There are H cages in C_(mmm)-Y_(3)HfH_(24),and attributed to the robust electron–phonon coupling and high electronic density of states of hydrogen at the Fermi level,it demonstrates near-room temperature superconductivity with a T_(c)of 275K at 250GPa.Our work makes contributions to the understanding of the fundamental properties of ternary hydrides under high pressure and provides essential references for further research in this field.
基金supported by the National Key R&D Program of China(Gran Nos.2022YFA1402304 and 2022YFA1402802)the National Natural Science Foundation of China(Grant Nos.12494591,12122405,12274169,and 92165204)+4 种基金Program for Science and Technology Innovation Team in Zhejiang(Grant No.2021R01004)Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)Guangdong Fundamental Research Center for Magnetoelectric Physics(2024B0303390001)Guangdong Provincial Quantum Science Strategic Initiative(Grant No.GDZX2401010)the Fundamental Research Funds for the Central Universities。
文摘The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the realization of superconductivity in compressively strained La_(3)Ni_(2)O_(7)thin films grown on the SrLaAlO_(4)substrates,with a T_(c)exceeding 40 K,represents a significant step toward this goal.Here,we investigate the influence of film thickness and carrier doping on the electronic structure of La_(3)Ni_(2)O_(7)thin films,ranging from 0.5 to 3 unit cells,using first-principles calculations.For a 2 unit-cell film with an optimal doping concentration of 0.3 hole per formula unit(0.15 hole/Ni),the Ni-d_(z^(2))interlayer bonding state crosses the Fermi level,resulting in the formation ofγpockets at the Fermi surface.These findings align with angle-resolved photoemission spectroscopy experimental data.Our results provide theoretical validation for the recent experimental discovery of ambient-pressure superconductivity in La_(3)Ni_(2)O_(7)thin films and underscore the significant impact of film thickness and carrier doping on electronic property modulation.
基金supported by the National Natural Science Foundation of China(Grant Nos.12122405,12274169,and 11574109)the Fundamental Research Funds for the Central Universities。
文摘The high-pressure phase diagram of the Nb-Ti binary system at 0 K is explored by systematic crystal structure prediction.The results highlight a novel niobium-rich bcc phase,Nb_(7)Ti,which is the only dynamically stable ordered Nb-Ti compound under ambient pressure.Extensive first-principles calculations have provided insights into the electronic structure,bonding and superconducting properties of Nb_(7)Ti.The superconducting transition temperature(T_(c))for Nb_(7)Ti at ambient pressure is estimated within the framework of BCS theory to be about 17.5 K,which is significantly higher—nearly double—that of the widely utilized NbTi alloy.Furthermore,the results unveil that the high T_(c) is mainly attributed to the unique ordered lattice along with the strong electron-phonon coupling driven by interatomic interactions at mid-frequency and phonon softening induced by low-frequency Fermi surface nesting.Valuable insights are provided for the subsequent synthesis of application-oriented superconductors at low pressure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12274169,12122405,and 52072188)the National Key Research and Development Program of China(Grant No.2022YFA1402304)+1 种基金the Program for Science and Technology Innovation Team in Zhejiang Province,China(Grant No.2021R01004)the Fundamental Research Funds for the Central Universities.
文摘Two-dimensional(2D)superconductors have attracted significant research interest due to their promising potential applications in optoelectronic and microelectronic devices.Herein,we employ first-principles calculations to predicted a new 2D conventional superconductor,Tc_(2)B_(2),demonstrating its stable structural configuration.Remarkably,under biaxial strain,the superconducting transition temperature(T_(c))of Tc_(2)B_(2)demonstrates a significant enhancement,achieving 19.5 K under 3%compressive strain and 9.2 K under 11%tensile strain.Our study reveals that strain-induced modifications in Fermi surface topology significantly enhance the Fermi surface nesting effect,which amplifies electron–phonon coupling interactions and consequently elevates Tc.Additionally,the presence of the Lifshitz transition results in a more pronounced rise in Tc under compressive strain compared to tensile strain.These insights offer important theoretical guidance for designing 2D superconductors with high-Tc through strain modulation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11904067)。
文摘Perovskites have garnered significant attention in recent years. However, the presence of La atoms at the B-site in ABX_(3) structures has not yet been observed. Under high pressure, perovskites exhibit unexpected phase transitions. In this study, we report the discovery of SbLaO_(3) under ambient pressure, with a space group of R3m. Mechanical property calculations indicate that it is a brittle material, and it possesses a band gap of 4.0266 e V, classifying it as an insulator.We also investigate the phase at 300 GPa, where the space group shifts to P2_(1/m). Additionally, the P2_(1/m) phase of LaInO_(3) under 300 GPa is explored. Ab initio molecular dynamics calculations reveal that the melting point of SbLaO_(3) is exceptionally high. The inclusion of Sb alters the electronic structure compared with LaInO_(3), and the Vickers hardness(H_(v)) is estimated to reach 20.97 GPa. This research provides insights into the phase transitions of perovskites under high pressure.
基金supported by the“Pioneer”and“Leading Goose”R&D Program of Zhejiang Province(Grant No.2022C01053)Zhejiang Provincial Natural Science Foundation of China(Grant No.LQ23A040010)+5 种基金the Open Fund of the State Key Laboratory of Spintronics Devices and Technologies(Grant No.SPL-2404)Zhejiang Provincial Natural Science Foundation of China(Grant No.Y24F050044)the National Natural Science Foundation of China(Grant Nos.12274169 and 12122405)M.M.acknowledges NSF DMR 1848141,OAC 2117956the Camille and Henry Dreyfus Foundation,and CSU RSCA grantsParts of the calculations were performed in the High Performance。
文摘Using first-principles evolutionary crystal structure prediction,we systematically investigate scandium polychlorides across 50-300 GPa,predicting multiple thermodynamically stable phases ScCl,ScCl_(2),ScCl_(3),ScCl_(5),and ScCl_(7)with unconventional stoichiometries.The exceptional stability of these compounds stems from the mutually compatible crystal orbitals of the Sc and Cl sublattices,strong ionic interactions,and the formation of Cl-Cl homobonds.These factors play critical roles in stabilizing scandium chloride compounds with various unconventional stoichiometries.Notably highpressure novel ScCl phases with P63/mmc and Pm-3m symmetries can be metastable at ambient pressure upon decompression and convert into superconductive electrides.Pm-3-ScCl_(7)exhibits significant pressure-modulated superconductivity,featuring an enhancement of T_(c)to 10.91 K at a low pressure of 75 GPa.In addition,the universal superconductivity found in the Pm-3 structured chlorides suggests a promising structural prototype for pressure-tunable superconductors.
基金supported by the National Natural Science Foundation of China(Grant Nos.11904067,12122405,52072188,1227416951632002)。
文摘Recently,a breakthrough in the high-pressure synthesis of sp^(3)-bonded clathrate-like R-3m-L_(a)B_(8)featuring Latrapped B_(26)cages was achieved.Although the superconducting critical temperature(T_(c))and Vickers hardness(H_(v))of L_(a)B_(8)were estimated,the anisotropic superconductivity and superconducting gap nature remain unclear.The stability of pure B_(26)cages under ambient conditions is of interest for exploring the B_(26)hardness and the role of La atoms in the L_(a)B_(8)hardness.By resolving the Allen–Dynes modified Mc Millan equation and the anisotropic Eliashberg equations,it was found that L_(a)B_(8)exhibits anisotropic single-gap superconductivity with T_(c)=19.0~26.5 K,and the superconducting gap anisotropic ratio reaches 48.50%at 5 K.Most significantly,our work fundamentally validated the coupling of B-2p orbitals with the optical double-degenerate E_(g)phonon modes and A_(g)phonon mode from a novel perspective.The H_(v)of B_(26)cages was determined to be 18.6 GPa,which is lower than that of La-trapped B_(26)cages(i.e.,L_(a)B_(8)),indicating that La acts as a hardness enhancer for L_(a)B_(8).
基金Project supported by the National Key R&D Program of China (Grant No.2022YFA1405500)the National Natural Science Foundation of China (Grant Nos.52372257 and 52072188)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University (Grant No.IRT-15R23)the Zhejiang Provincial Science and Technology Innovation Team (Grant No.2021R01004)。
文摘Element superconductors with the single atoms provide clean and fundamental platforms for studying superconductivity.Although elements with d electrons are usually not favored by conventional BCS,the record superconducting critical temperature(T_(c))in element scandium(S_(c))has further ignited the intensive attention on transition metals.The element molybdenum(M_o)with a half-full d-orbital is studied in our work,which fills the gap in the study of Mo under high pressure and investigates the pressure dependence of superconductivity.In this work,we exhibit a robust superconductivity of Mo in the pressure range of 5 GPa to 160 GPa via high-pressure electrical transport measurements,the T_(c) varies at a rate of0.013 K/GPa to 8.56 K at 160 GPa.Moreover,the superconductivity is evidenced by the T_(c) shifting to lower temperature under applied magnetic fields,and the upper critical magnetic fields are extrapolated by the WHH equation and GL equation;the results indicate that the maximum upper critical magnetic field is estimated to be 8.24 T at 137 GPa.We further investigate the superconducting mechanism of Mo,the theoretical calculations indicate that the superconductivity can be attributed to the strong coupling between the electrons from the partially filled d band and the phonons from the frequency zone of 200-400 cm^(-1).
基金supported by the National Natural Science Foundation of China(Grant Nos.12122405 and 12274169)the National Key Research and Development Program of China(Grant Nos.2022YFA1402304 and 2023YFA1406200)the Fundamental Research Funds for the Central Universities。
文摘Two-dimensional(2D)materials have demonstrated promising prospects owing to their distinctive electronic properties and exceptional mechanical properties.Among them,2D superconductors with T_(c) above the boiling point of liquid nitrogen(77 K)will exhibit tremendous applicable value in the future.Here,we design two 2D superconductors Na(BC)_(2) and K(BC)_(2) with MgB2-like structures,which are theoretically predicted to host T_(c) as high as 99 and 102 K,respectively.The origin of such high T_(c) is ascribed to the presence of both𝜎-bonding bands and van Hove singularity at the Fermi level.Furthermore,T_(c) of Na(BC)_(2) is boosted up to 153K with a biaxial strain of 5%,which sets a new record among 2D superconductors.The predictions of Na(BC)_(2) and K(BC)_(2) open the door to explore 2D high-temperature superconductors and provide a potential future for developing new applications in 2D materials.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12122405,51632002,and 11974133)the Program for Changjiang Scholars and Innovative Research Team in Universities(Grant No.IRT 15R23)+1 种基金financial support from the Engineering and Physical Sciences Research Council(Grant No.EP/P022596/1)。
文摘Sulfur and lanthanum hydrides under compression display superconducting states with high observed critical temperatures.It has been recently demonstrated that carbonaceous sulfur hydride displays room temperature superconductivity.However,this phenomenon has been observed only at very high pressure.Here,we theoretically search for superconductors with very high critical temperatures,but at much lower pressures.We describe two of such sodalite-type clathrate hydrides,YbH6 and LuH6.These hydrides are metastable and are predicted to superconduct with T_(c)~145 K at 70 GPa and T_(c)~273 K at 100 GPa,respectively.This striking result is a consequence of the strong interrelationship between the f states present at the Fermi level,structural stability,and the final T_(c) value.For example,TmH6,with unfilled 4f orbitals,is stable at 50 GPa,but has a relatively low value of T_(c) of 25 K.The YbH6 and LuH6 compounds,with their filled f-shells,exhibit prominent phonon"softening",which leads to a strong electron-phonon coupling,and as a result,an increase in T_(c).
基金This work was supported by the National Key R&D Program of China(Grant Nos.2018YFA0305900 and 2022YFA1402304)the National Natural Science Foundation of China(Grant Nos.12122405,52072188,and 12274169)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT_15R23)a Jilin Provincial Science and Technology Development Project(Grant No.20210509038RQ).Some of the calculations were performed at the High Performance Computing Center of Jilin University and on TianHe-1(A)at the National Supercomputer Center in Tianjin.
文摘Recently,room-temperature superconductivity has been reported in a nitrogen-doped lutetium hydride at near-ambient pressure[Dasenbrock-Gammon et al.,Nature 615,244(2023)].The superconducting properties might arise from Fm3m-LuH_(3)−δNε.Here,we systematically study the phase diagram of Lu–N–H at 1 GPa using first-principles calculations,and we do not find any thermodynamically stable ternary compounds.In addition,we calculate the dynamic stability and superconducting properties of N-doped Fm3m-LuH_(3) using the virtual crystal approximation(VCA)and the supercell method.The R3m-Lu_(2)H_(5)N predicted using the supercell method could be dynamically stable at 50 GPa,with a T_(c) of 27 K.According to the VCA method,the highest T_(c) is 22 K,obtained with 1%N-doping at 30 GPa.Moreover,the doping of nitrogen atoms into Fm3m-LuH_(3) slightly enhances T_(c),but raises the dynamically stable pressure.Our theoretical results show that the T_(c) values of N-doped LuH_(3) estimated using the Allen–Dynes-modified McMillan equation are much lower than room temperature.
基金supported by the National Natural Science Foundation of China(Grant Nos.12104127 and 22131006)the Doctoral Starting Up Foundation of Hebei Normal University for Nationalities(Grant No.DR2020001)+1 种基金the Clean Energy(Carbon Peaking and Carbon Neutrality)Industry Research Institute of Chengde(Grant No.202205B090)the Natural Science Foundation of Shandong Province(Grant No.ZR2020QA060)。
文摘On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorable mechanical properties using boron-rich compounds.In this paper,first-principles calculations reveal the existence of an unprecedented family of tetragonal pentaborides MB_(5)(M=Na,K,Rb,Ca,Sr,Ba,Sc,and Y),comprising B_(20)cages and centered metal atoms acting as stabilizers and electron donors to the boron sublattice.These compounds exhibit both superconductivity and high hardness,with the maximum superconducting transition temperature T_(c)of 18.6 K being achieved in RbB5 and the peak Vickers hardness Hv of 35.1 GPa being achieved in KB_(5)at 1 atm.The combination of these properties is particularly evident in KB_(5),RbB5,and BaB5,with Tc values of∼14.7,18.6,and 16.3 K and H_(v)values of∼35.1,32.4,and 33.8 GPa,respectively.The results presented here reveal that pentaborides can provide a framework for exploring and designing novel superconducting materials with favorable hardness at achievable pressures and even under ambient conditions.
基金Project supported by the National Key R&D Program of China(Grant Nos.2018YFA0305900 and 2016YFB0201204)the National Natural Science Foundation of China(Grant Nos.51632002,51572108,11574109,91745203,and 11634004)+1 种基金Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT 15R23)National Fund for Fostering Talents of Basic Science,China(Grant No.J1103202)
文摘First-principles evolutionary calculation was performed to search for all probable stable Ga–Te compounds at extreme pressure. In addition to the well-known structures of P6_3/mmc and Fm-3 m Ga Te and I4/m Ga_2 Te_5, several new structures were uncovered at high pressure, namely, orthorhombic I4/mmm GaTe_2 and monoclinic C2/m Ga Te_3, and all the Ga–Te structures stabilize up to a maximum pressure of 80 GPa. The calculation of the electronic energy band indicated that the high-pressure phases of the Ga–Te system are metallic, whereas the low-pressure phases are semiconductors. The electronic localization functions(ELFs) of the Ga–Te system were also calculated to explore the bond characteristics. The results showed that a covalent bond is formed at low pressure, however, this bond disappears at high pressure, and an ionic bond is formed at extreme pressure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11704143,51672102,51632002,and 11604023)the National Key Research and Development Program of China(Grant Nos.2018YFA0305900 and 2016YFB0201204)the Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT-15R23)
文摘Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literature.The energy difference of C2vand C3vstructures is qualitatively affected by the supercell size,and the 216-atom supercell could be proposed as the minimum to obtain stable configuration of substitutional S in diamond.Using supercells of up to 512 atoms,the donor level of substitutional S with C2vsymmetry is deep.
基金Project supported by the National Key R&D Program of China(Grant No.2018YFA0305900)the National Natural Science Foundation of China(Grant Nos.51632002,51572108,91745203,11634004,11174102,and 1174121)+2 种基金the National Key Research and Development Program of China(Grant No.2016YFB0201204)the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT 15R23)the National Fund for Fostering Talents of Basic Science,China(Grant No.J1103202)
文摘The variational and diffusion Monte Carlo approaches are used to study the ground-state properties of a hydrogen molecular ion in a spheroidal box. In this work, we successfully treat the zero-point motion of protons in the same formalism with as of electrons and avoid the Born–Oppenheimer approximation in density function theory. The study shows that the total energy increases with the decrease in volume, and that the distance between protons decreases as the pressure increases.Considering the motion of protons, the kinetic energy of the electron is higher than that of the fixed model under the same conditions and increases by 5%. The kinetic energy of the proton is found to be small under high pressure, which is only a fraction of the kinetic energy of the electron.
基金supported by the National Natural Science Foundation of China (Grant No. 11674122)。
文摘Pressure has an important effect on chemical bonds and their chemical properties. The atypical compounds NaCl_(3) and CsF_(3) are predicted to be stable at high pressure and show unique physical and chemical properties. By using ab initio random structure searching and density functional theory calculations, we predicted multiple thermodynamically stable atypical compounds, which are RbF_(2), RbF_(3), RbF_(4), and RbF_(5) in the pressure range of 0–300 GPa. In these stable compounds, homonuclear bondings of F_(3), F_(4), and F_(5) species are easily formed. The electron structure calculation showed that except for Fd-3 m phase of RbF_(2), these stable compounds are insulators and F 5 p orbitals play an important role in the Fermi level. It is interesting that the compounds RbF_(5) could be stable at nearly ambient pressure and 0 K which will stimulate experimental studies in the future.
基金Supported by the National Key Research and Development Program of China(Grant Nos.2016YFB0201204,2018YFA0703404,and 2017YFA0403704)the National Natural Science Foundation of China(Grant Nos.11574109 and 91745203)the Program for Changjiang Scholars and Innovative Research Team in Universities(Grant No.IRT_15R23).
文摘We conduct extensive research into the structures of Be_(x)Zn_(1-x)OO ternary alloys in a pressure range of 0-60GPa,using the ab initio total energy evolutionary algorithm and total energy calculations,finding several metastable structures.Our pressure-composition phase diagram is constructed using the enthalpy results.In addition,we calculate the electronic structures of the Be_(x)Zn_(1-x)OO structures and investigate the bandgap values at varying pressures and Be content.The calculated results show that the bandgap of the Be_(x)Zn_(1-x)OO ternary alloys increases with an increase in Be content at the same pressure.Moreover,the bandgap of the Be_(x)Zn_(1-x)OO ternary alloys increases with the increasing pressure with fixed Be content.At the same Be content,the formation enthalpy of the Be_(x)Zn_(1-x)OO ternary alloys first decreases,then increases with the increasing pressure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574109,51632002,51572108,91745203,and 11574112)the National Key Research and Development Program of China(Grant Nos.2016YFB0201204 and 2018YFA0305900)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT 15R23)the National Fund for Fostering Talents of Basic Science of China(Grant No.J1103202).
文摘Ammonium iodine(NH4I)as an important member of hydrogen-rich compounds has attracted a great deal of attention owing to its interesting structural changes triggered by the relative orientations of adjacent ammonium ions.Previous studies of ammonium iodide have remained in the low pressure range experimentally,which we first extended to so high pressure(250 GPa).We have investigated the structures of ammonium iodine under high pressure through ab initio evolutionary algorithm and total energy calculations based on density functional theory.The static enthalpy calculations show that phase V is stable until 85 GPa where a new phase Ibam is identified.Calculations of phonon spectra show that the Ibam phase is stable between 85 GPa and 101 GPa and the Cm phase is stable up to 130 GPa.In addition,ammonium iodine dissociates into NH3,H2,and I2 at 74 GPa.Subsequently,we analyzed phonon spectra and electronic band structures,finding that phonon softening is not the reason of dissociation and NH4I is always a semiconductor within the pressure range.
基金supported by the National Natural Science Foundation of China(Grant Nos.12122405,52072188,and 12274169)the National Key R&D Program of China(Grant Nos.2022YFA1402304,and 2023YFA1406200)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.xzy022023011,and xhj032021014-04)the Program for Science and Technology Innovation Team in Zhejiang(Grant No.2021R01004).
文摘Trilayer Ruddlesden-Popper phase La_(4)Ni_(3)O_(10) has been observed with T_(c) of~30 K at high pressure in a recent experiment,which further expanded the family of nickelate superconductors.In this study,we explored the effects of electronic correlations in La_(4)Ni_(3)O_(10) using density functional theory plus dynamical mean-field theory at ambient and high pressures.Our derived spectral functions and Fermi surface of the ambient pressure phase are nicely consistent with the experimental results by angleresolved photoemission spectroscopy,which emphasized the importance of electronic correlations in La_(4)Ni_(3)O_(10).We also found the electronic correlations in pressurized La_(4)Ni_(3)O_(10) are both orbital-dependent and layer-dependent due to the presence of Hund’s rule coupling.There is a competition between the Hund’s rule coupling and the crystal-field splitting,and therefore,the Ni-O layers with weaker crystal-field splitting energy would have stronger electronic correlations.
基金supported by the National Key R&D Program of China(Grant Nos.2022YFA1402304,and 2022YFA1402802)the National Natural Science Foundation of China(Grant Nos.12122405,52072188,12274169,12494591,and 92165204)+4 种基金the Program for Science and Technology Innovation Team in Zhejiang(Grant No.2021R01004)the Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)the Fundamental Research Funds for the Central Universities(Grant Nos.xzy022023011,and xhj03202101404)the Research Center for Magnetoelectric Physics of Guangdong Province(Grant No.2024B0303390001)the Guangdong Provincial Quantum Science Strategic Initiative(Grant No.GDXZ2401010)。
文摘The recent transport measurements of La_(3)Ni_(2)O_(7)uncovered a“right-triangle”shape of the superconducting dome in the pressure-temperature(P-T)phase diagram.Motivated by this,we perform theoretical first-principles studies of La_(3)Ni_(2)O_(7)with the pressure ranging from 0 to 100 GPa.Notably,we reveal a pressure dependence of the Ni-d_(z^(2))electron density at the Fermi energy(n_(z)^(E_(F)))that highly coincides with such shape.On this basis,we further explore the electronic structure under uniaxial stress.By tracking the stress response of n_(z)^(E_(F)),we propose that superconductivity can be achieved by applying only ~2GPa of compression along the c axis.The idea is further exemplified from the perspectives of lattice distortion,band structure,Fermi surface and superconducting phase coherence.We also discuss the possible charge modulation under the stress and provide an insight into the relation between nz E Fand the superconducting T_(c)in La_(3)Ni_(2)O_(7)system.Our study provides new routes to the search of high-T_(c)superconductors in future experiments.
