Electric quadrupole moments of low-lying excited states of Yb^+are calculated by relativistic coupled-cluster theory with perturbations from external fields.The field-dependent energy differentiation provides accurate...Electric quadrupole moments of low-lying excited states of Yb^+are calculated by relativistic coupled-cluster theory with perturbations from external fields.The field-dependent energy differentiation provides accurate values of the electric quadrupole moments of^2P3/2,^2D3/2,5/2,and^2F5/2,7/2 states which agree well with experimental values.The important role of the electronic correlation to the electric quadrupole moments is investigated.Our calculations indicate the early dispute of the electric quadrupole moment of the Yb^+(2F7/2)state for which the measured and theoretical values have a large discrepancy.These electric quadrupole moment values can help us to determine the electric quadrupole shifts in start-of-the-art experiments of the Yb+ion.展开更多
First-principles calculations and Monte Carlo simulations reveal that single-layer and double-layer VX_(2)(X=Cl,Br)can be tuned from antiferromagnetic(AFM)semiconductors to ferromagnetic(FM)state when biaxial tensile ...First-principles calculations and Monte Carlo simulations reveal that single-layer and double-layer VX_(2)(X=Cl,Br)can be tuned from antiferromagnetic(AFM)semiconductors to ferromagnetic(FM)state when biaxial tensile stress is applied.Their ground states are all T phase.The biaxial tensile stress at the phase transition point of the double-layer VX_(2) is larger than that of the single-layer VX_(2).The direct band gaps can be also manipulated by biaxial tensile stress as they increases with increasing tensile stress to a critical point and then decreases.The Neel temperature(´TN)of double-layer VX_(2) are higher than that of single-layer.As the stress increases,the TN of all materials tend to increase.The magnetic moment increases with the increase of biaxial tensile stress,and which become insensitive to stress after the phase transition points.Our research provides a method to control the electronic and magnetic properties of VX_(2) by stress,and the single-layer and double-layer VX_(2) may have potential applications in nano spintronic devices.展开更多
In this paper,we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations.By considering the electronic correlatio...In this paper,we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations.By considering the electronic correlation effect,we predicted the ground-state structure of CrTe to be NiAs-type(space group P63/mmc)structure at ambient pressure,consistent with the experimental observation.Moreover,we found two extra meta-stable Cmca and R3m structures which have negative formation enthalpy and stable phonon dispersion at ambient pressure.The Cmca structure is a layered antiferromagnetic metal.The cleaved energy of a single layer is 0.464 J/m^(2),indicating the possible synthesis of CrTe monolayer.The R3m structure is a ferromagnetic half-metal.When external pressure is applied,the ground-state structure of CrTe transitions from P63/mmc structure to R3m structure at a pressure of 34 GPa,then to Fm3m structure at 42 GPa.We thought these results help to motivate experimental studies of the CrTe compounds in the application of spintronics.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11874064)the Strategic Priority and the Research Program of the Chinese Academy of Sciences(Grant No.XDB21030300)+3 种基金the National Key Research and Development Program of China(Grant No.2016YFA0302104)Yong Liu acknowledges the Project of Hebei Educational Department,China(Grant No.ZD2018015)the Natural Science Foundation of Hebei Province,China(Grant No.A2019203507)Bing-Bing Suo acknowledges the financial support from the National Natural Science foundation of China(Grant Nos.21673174 and 21873077).
文摘Electric quadrupole moments of low-lying excited states of Yb^+are calculated by relativistic coupled-cluster theory with perturbations from external fields.The field-dependent energy differentiation provides accurate values of the electric quadrupole moments of^2P3/2,^2D3/2,5/2,and^2F5/2,7/2 states which agree well with experimental values.The important role of the electronic correlation to the electric quadrupole moments is investigated.Our calculations indicate the early dispute of the electric quadrupole moment of the Yb^+(2F7/2)state for which the measured and theoretical values have a large discrepancy.These electric quadrupole moment values can help us to determine the electric quadrupole shifts in start-of-the-art experiments of the Yb+ion.
基金supported by the National Natural Science Foundation of China(Grant Nos.11904312 and 11904313)the Project of Hebei Educational Department,China(Grant Nos.ZD2018015 and QN2018012)the Natural Science Foundation of Hebei Province,China(Grant No.A2019203507).
文摘First-principles calculations and Monte Carlo simulations reveal that single-layer and double-layer VX_(2)(X=Cl,Br)can be tuned from antiferromagnetic(AFM)semiconductors to ferromagnetic(FM)state when biaxial tensile stress is applied.Their ground states are all T phase.The biaxial tensile stress at the phase transition point of the double-layer VX_(2) is larger than that of the single-layer VX_(2).The direct band gaps can be also manipulated by biaxial tensile stress as they increases with increasing tensile stress to a critical point and then decreases.The Neel temperature(´TN)of double-layer VX_(2) are higher than that of single-layer.As the stress increases,the TN of all materials tend to increase.The magnetic moment increases with the increase of biaxial tensile stress,and which become insensitive to stress after the phase transition points.Our research provides a method to control the electronic and magnetic properties of VX_(2) by stress,and the single-layer and double-layer VX_(2) may have potential applications in nano spintronic devices.
基金This work was supported by the National Natural Science Foundation of China(Nos.11904312 and 11904313),the Project of Hebei Educational Department,China(Nos.ZD2018015 and QN2018012),the Natural Science Foundation of Hebei Province of China(No.A2020203027),the Doctor Foundation Project of Yanshan University(No.BL19008),and the Scientific Research Foundation of the Higher Education of Hebei Province,China(No.BJ2020015).The numerical calculations in this paper have been done on the supercomputing system in the High Performance Computing Center of Yanshan University.
文摘In this paper,we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations.By considering the electronic correlation effect,we predicted the ground-state structure of CrTe to be NiAs-type(space group P63/mmc)structure at ambient pressure,consistent with the experimental observation.Moreover,we found two extra meta-stable Cmca and R3m structures which have negative formation enthalpy and stable phonon dispersion at ambient pressure.The Cmca structure is a layered antiferromagnetic metal.The cleaved energy of a single layer is 0.464 J/m^(2),indicating the possible synthesis of CrTe monolayer.The R3m structure is a ferromagnetic half-metal.When external pressure is applied,the ground-state structure of CrTe transitions from P63/mmc structure to R3m structure at a pressure of 34 GPa,then to Fm3m structure at 42 GPa.We thought these results help to motivate experimental studies of the CrTe compounds in the application of spintronics.