The structural, electronic and elastic properties of Rb As systems （RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3As in NaaAs, Cu3P and Li3Bi structures, and Rb5As4 in the A5B4 structure） a...The structural, electronic and elastic properties of Rb As systems （RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3As in NaaAs, Cu3P and Li3Bi structures, and Rb5As4 in the A5B4 structure） are investigated with the generalized gradient approximation in tile frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli （to fit Murnaghan＇s equation of state） of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young＇s modulus, the shear modulus, Poisson＇s ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.展开更多
The structural, elastic, and electronic properties of a series of lanthanide hexaborides（Ln B6） have been investigated by performing ab initio calculations based on the density functional theory using the Vienna ab ...The structural, elastic, and electronic properties of a series of lanthanide hexaborides（Ln B6） have been investigated by performing ab initio calculations based on the density functional theory using the Vienna ab initio simulation package.The calculated lattice and elastic constants of Ln B6 are in good agreement with the available experimental data and other theoretical results. The polycrystalline Young＇s modulus, shear modulus, the ratio of bulk to shear modulus B/G, Poisson＇s ratios, Zener anisotropy factors, as well as the Debye temperature are calculated, and all of the properties display some regularity with increasing atomic number of lanthanide atoms, whereas anomalies are observed for Eu B6 and Yb B6. In addition, detailed electronic structure calculations are carried out to shed light on the peculiar elastic properties of Ln B6.The total density of states demonstrates the existence of a pseudogap and indicates lower structure stability of Eu B6 and Yb B6 compared with others.展开更多
A systematic density functional theory and wave function theory investigation on the geometrical and electronic properties of A1Aun0/＂ （n = 2-4） clusters has been performed in this work. A1Aun- anions prove to poss...A systematic density functional theory and wave function theory investigation on the geometrical and electronic properties of A1Aun0/＂ （n = 2-4） clusters has been performed in this work. A1Aun- anions prove to possess ground states of the V-shaped C2v A1Au2, umbrella-shaped C3v A1Au3, and perfect tetrahedral Td A1Au4＂, while their neutrals favor the V-shaped CEv A1Au2, perfect planar triangular D3h A1Au3, and severely distorted Cs A1Au4, respectively. Aluminum aurides appear to be analogous to the corresponding aluminum hydrides, expect C~ A1Au4. Molecular orbitals （MOs） analyses also support this conclusion. Detailed orbital analyses indicate that Au 6s makes 94-96% and Au 5d makes 6-4% contribution to the Au-based orbitals in A1-Au bonds, which is smaller than the BAun0/- series, partially reflecting the relativistic effect of gold. The one-electron detachment energies of the anions and characteristic stretching vibrational frequencies of A1-Au bonds between 100-400 cm-1 have been calculated to facilitate future experimental characterization of these clusters.展开更多
In this work, we have investigated the electronic and optical properties of the technologically important rare earth oxide compounds—X2O3 (X: Gd, Tb) using the density functional theory within the GGA. The band struc...In this work, we have investigated the electronic and optical properties of the technologically important rare earth oxide compounds—X2O3 (X: Gd, Tb) using the density functional theory within the GGA. The band structure of X2O3 have been calculated along high symmetry directions in the first brillouin zone. The real and imaginary parts of dilectric functions and the other optical responses such as energy-loss function, the effective number of valence electrons and the effective optical dielectric constants of the rare earth sesquioxides (Gd2O3 and Tb2O3) were calculated.展开更多
We study the structural, elastic and electronic properties of perovskite insulator LaAlO3 using two different methods: the full-potential linearized augmented plane wave method and the pseudo-potential plane wave sche...We study the structural, elastic and electronic properties of perovskite insulator LaAlO3 using two different methods: the full-potential linearized augmented plane wave method and the pseudo-potential plane wave scheme in the frame of generalized gradient approximation and local density approximation GGA + mBJ. We have evaluated the ground state quantities. Also, we have presented the results of the band structure and densities of states. These results are in favourable agreement with previous theoretical works and the existing experimental data. To complete the fundamental characteristics of this compound, we have analyzed the thermodynamic properties.展开更多
The structural, electronic, elastic and magnetic properties of cerium, praseodymium and their hydrides REH x（RE=Ce, Pr and x=2, 3） were investigated by the first principles calculations based on density functional t...The structural, electronic, elastic and magnetic properties of cerium, praseodymium and their hydrides REH x（RE=Ce, Pr and x=2, 3） were investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation package. At zero pressure all the hydrides were stable in the ferromagnetic state. The calculated lattice parameters were in good agreement with the experimental results. The bulk modulus decreased with the increase in the hydrogen content for these hydrides. The electronic structure revealed that di-hydrides were metallic whereas trihydrides were half metallic at zero pressure. A pressure-induced structural phase transition from cubic to hexagonal phase was predicted in these hydrides. The computed elastic constants indicated that these hydrides were mechanically stable at zero pressure. The calculated Debye temperature values were in good agreement with experimental and other theoretical results. A half metallic to metallic transition was also observed in REH3 under high pressure. Ferromagnetism was quenched in these hydrides at high pressures.展开更多
Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of rubidium metal hydrides RbMH4（M = B, Al, Ga） for five different crystal structures, nam...Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of rubidium metal hydrides RbMH4（M = B, Al, Ga） for five different crystal structures, namely hexagonal（P63mc）, tetragonal（P42/nmc）, tetragonal（P421c）, orthorhombic（Pnma） and monoclinic（P21/c）. Among the considered structures, tetragonal（P421c） phase is found to be the most stable one for these metal hydrides at normal pressure. A pressure-induced structural phase transition from tetragonal（P421c） to monoclinic（P21/c） phase is observed in all the three metal hydrides. The electronic structure reveals that these hydrides are wide band gap semiconductors. The calculated elastic constants indicate that these alkali metal tetrahydrides are mechanically stable at normal pressure.展开更多
The structures under different pressures, elastic properties, electronic structures and lattice vibrations of the X_2N_2O（X = C, Si, Ge） compounds are investigated by using the first-principle method. Based on the p...The structures under different pressures, elastic properties, electronic structures and lattice vibrations of the X_2N_2O（X = C, Si, Ge） compounds are investigated by using the first-principle method. Based on the phonon density of state,the thermodynamic properties of the present compounds are studied under different pressures and at different temperatures. The structural parameters including the bond lengths and bond angles are in agreement with available experimental measurements and theoretical calculations. We employ the elastic theory to calculate the nine independent elastic constants（C_（ij）） and the derived elastic moduli（B, G, E, v）. Results indicate that these X_2N_2O（X = C, Si, Ge） compounds are mechanically stable and show the brittle behaviors. The electronic properties of the present compounds are analyzed by using the band structure and density of states. The phonon dispersion calculations imply that the present compounds are dynamically stable. Based on the quasi-harmonic approximation, the calculations of the specific heat indicate that the temperature in a range of 0 K–1500 K and pressure in a range of 0 GPa–40 GPa have a large effect on the thermal quantities of Ge_2N_2O,compared with on those of the C_2N_2O and Si_2N_2O compounds.展开更多
Ab initio optimizations at HF /6-31G level and subsequent electrostatic potential calculations have been performed for a group of 68solvent mo lecules.Linear correlation of solv ent softness to the theoretical desc...Ab initio optimizations at HF /6-31G level and subsequent electrostatic potential calculations have been performed for a group of 68solvent mo lecules.Linear correlation of solv ent softness to the theoretical desc riptors has been established by using multiple r egression.The relationship can be well expressed as follows:D s =28.3844I-3.3965V min -10.9162Π+22.7684σ tot 2 +4.5040(N=65,R=0.960,R CV =0.953,SD =3.5557,F=175.66),and shows good predictie power.展开更多
The properties and electronic structure of Fe under pressures of 0-30GPa have been studied by flrst principles employing the density functional theory（DFT）,the ultra-soft pseudo-potentials（USPP）and the generalized...The properties and electronic structure of Fe under pressures of 0-30GPa have been studied by flrst principles employing the density functional theory（DFT）,the ultra-soft pseudo-potentials（USPP）and the generalized gradient approximation（GGA）.The calculating results show that there is a structural transition from magnetic body-centered cubic（bcc）to nonmagnetic hexagonal-close-packed（hcp）structure for Fe around 11 GPa pressure.There is a pseudogap both in the density of states（DOS）for bcc and hcp Fe.The pseudogap of bcc Fe is deeper and wider than that of hcp Fe.The elastic modulus is obtained by Voigt-Reuss-Hill averaging scheme.The results indicate that the elastic properties of bcc Fe enhance with pressure except for elastic stiffness constant C11, shear modulus G and elastic modulus E at the transition pressure,while the elastic properties of hcp Fe increase linearly with pressure.Magnetic bcc Fe is ductile,and hcp Fe becomes ductile from brittle around 25 GPa.展开更多
The low magnetic moment （MM） in diluted magnetic semiconductors （DMS） at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors （CMS）.This work reports an ab-initio...The low magnetic moment （MM） in diluted magnetic semiconductors （DMS） at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors （CMS）.This work reports an ab-initio investigation of the electronic structures and magnetic properties of ZnO in a zinc-blende （ZB） structure doped with nickel ions. Ni-doped ZnO-based DMS and CMS exhibit a dominance of ferromagnetic coupling over antiferromagnetic. A robust increase in the magnetization has been observed as a function of Ni impurity levels. This material favors short-range magnetic interactions at the ground state, suggesting that the observed ferromagnetism is defined by the double exchange mechanism. The spin-polarized density of states （DOS） of Ni-doped ZnO characterizes it as half-metallic with a considerable energy gap for up-spin components and as metallic for-down spins. Half metallic Ni：ZnO based magnetic semiconductors with high magnetization are expected to have potential applications in spintronics.展开更多
The reaction of DyCl_(3)·6H_(2)O with a rigid diacylhydrazone ligand(H_(2)L)afforded a trinuclear precursor[Dy_(3)L_(2)Cl_(3)(H_(2)O)_(2)(CH_(3)OH)]Cl_(2)·3CH_(3)OH(1).The replacement of the Cl-ions and the ...The reaction of DyCl_(3)·6H_(2)O with a rigid diacylhydrazone ligand(H_(2)L)afforded a trinuclear precursor[Dy_(3)L_(2)Cl_(3)(H_(2)O)_(2)(CH_(3)OH)]Cl_(2)·3CH_(3)OH(1).The replacement of the Cl-ions and the coordinating solvents by the aryloxides ligands(Lx)-yields three trinuclear complexes[Dy_(3)L_(2)(Lx)_(5)]·nsol(x=1,2-naphthol(2);x=2,7-hydroxycoumarin(3);and x=3,phenol(4)).In complexes 2-4,two end Dy^(3+)centers adopt almost identical N_(4)O_(4) coordination sphere of D6h geometry while the central one adopts N_(4)O_(5) coordination sphere in Cs geometry.Magnetic measurements reveal weak antiferromagnetic interactions in the hydrated samples 2e-4e and two-step slow relaxation process under zero dc field with effective energy barriers Ueff of 439 and 91 K,353 and 40 K,466 and 89 K for SR and FR in 2e-4e,respectively.Such dynamic magnetic behaviour for 4 persists in the magnetically diluted sample of 4@Y.Complex 4 possesses the short Dy-O_(aryloxide) bond distance of 2.055(18)Å,and the largest Ueff among the reported linear trinuclear dysprosium complexes.Moreover,the functionalized aryloxides ligands(Lx)-show photoluminescence via intramolecular energy transfer,making 2e-4e luminescent Dy^(3+)SMMs with high energy barriers.展开更多
文摘The structural, electronic and elastic properties of Rb As systems （RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3As in NaaAs, Cu3P and Li3Bi structures, and Rb5As4 in the A5B4 structure） are investigated with the generalized gradient approximation in tile frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli （to fit Murnaghan＇s equation of state） of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young＇s modulus, the shear modulus, Poisson＇s ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.
文摘The structural, elastic, and electronic properties of a series of lanthanide hexaborides（Ln B6） have been investigated by performing ab initio calculations based on the density functional theory using the Vienna ab initio simulation package.The calculated lattice and elastic constants of Ln B6 are in good agreement with the available experimental data and other theoretical results. The polycrystalline Young＇s modulus, shear modulus, the ratio of bulk to shear modulus B/G, Poisson＇s ratios, Zener anisotropy factors, as well as the Debye temperature are calculated, and all of the properties display some regularity with increasing atomic number of lanthanide atoms, whereas anomalies are observed for Eu B6 and Yb B6. In addition, detailed electronic structure calculations are carried out to shed light on the peculiar elastic properties of Ln B6.The total density of states demonstrates the existence of a pseudogap and indicates lower structure stability of Eu B6 and Yb B6 compared with others.
基金supported by the North China University of Water Conservancy and Electric Power High-level experts Scientific Research Foundation(No.201114)
文摘A systematic density functional theory and wave function theory investigation on the geometrical and electronic properties of A1Aun0/＂ （n = 2-4） clusters has been performed in this work. A1Aun- anions prove to possess ground states of the V-shaped C2v A1Au2, umbrella-shaped C3v A1Au3, and perfect tetrahedral Td A1Au4＂, while their neutrals favor the V-shaped CEv A1Au2, perfect planar triangular D3h A1Au3, and severely distorted Cs A1Au4, respectively. Aluminum aurides appear to be analogous to the corresponding aluminum hydrides, expect C~ A1Au4. Molecular orbitals （MOs） analyses also support this conclusion. Detailed orbital analyses indicate that Au 6s makes 94-96% and Au 5d makes 6-4% contribution to the Au-based orbitals in A1-Au bonds, which is smaller than the BAun0/- series, partially reflecting the relativistic effect of gold. The one-electron detachment energies of the anions and characteristic stretching vibrational frequencies of A1-Au bonds between 100-400 cm-1 have been calculated to facilitate future experimental characterization of these clusters.
文摘In this work, we have investigated the electronic and optical properties of the technologically important rare earth oxide compounds—X2O3 (X: Gd, Tb) using the density functional theory within the GGA. The band structure of X2O3 have been calculated along high symmetry directions in the first brillouin zone. The real and imaginary parts of dilectric functions and the other optical responses such as energy-loss function, the effective number of valence electrons and the effective optical dielectric constants of the rare earth sesquioxides (Gd2O3 and Tb2O3) were calculated.
文摘We study the structural, elastic and electronic properties of perovskite insulator LaAlO3 using two different methods: the full-potential linearized augmented plane wave method and the pseudo-potential plane wave scheme in the frame of generalized gradient approximation and local density approximation GGA + mBJ. We have evaluated the ground state quantities. Also, we have presented the results of the band structure and densities of states. These results are in favourable agreement with previous theoretical works and the existing experimental data. To complete the fundamental characteristics of this compound, we have analyzed the thermodynamic properties.
文摘The structural, electronic, elastic and magnetic properties of cerium, praseodymium and their hydrides REH x（RE=Ce, Pr and x=2, 3） were investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation package. At zero pressure all the hydrides were stable in the ferromagnetic state. The calculated lattice parameters were in good agreement with the experimental results. The bulk modulus decreased with the increase in the hydrogen content for these hydrides. The electronic structure revealed that di-hydrides were metallic whereas trihydrides were half metallic at zero pressure. A pressure-induced structural phase transition from cubic to hexagonal phase was predicted in these hydrides. The computed elastic constants indicated that these hydrides were mechanically stable at zero pressure. The calculated Debye temperature values were in good agreement with experimental and other theoretical results. A half metallic to metallic transition was also observed in REH3 under high pressure. Ferromagnetism was quenched in these hydrides at high pressures.
文摘Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of rubidium metal hydrides RbMH4（M = B, Al, Ga） for five different crystal structures, namely hexagonal（P63mc）, tetragonal（P42/nmc）, tetragonal（P421c）, orthorhombic（Pnma） and monoclinic（P21/c）. Among the considered structures, tetragonal（P421c） phase is found to be the most stable one for these metal hydrides at normal pressure. A pressure-induced structural phase transition from tetragonal（P421c） to monoclinic（P21/c） phase is observed in all the three metal hydrides. The electronic structure reveals that these hydrides are wide band gap semiconductors. The calculated elastic constants indicate that these alkali metal tetrahydrides are mechanically stable at normal pressure.
基金Project supported by the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-14-029Al)
文摘The structures under different pressures, elastic properties, electronic structures and lattice vibrations of the X_2N_2O（X = C, Si, Ge） compounds are investigated by using the first-principle method. Based on the phonon density of state,the thermodynamic properties of the present compounds are studied under different pressures and at different temperatures. The structural parameters including the bond lengths and bond angles are in agreement with available experimental measurements and theoretical calculations. We employ the elastic theory to calculate the nine independent elastic constants（C_（ij）） and the derived elastic moduli（B, G, E, v）. Results indicate that these X_2N_2O（X = C, Si, Ge） compounds are mechanically stable and show the brittle behaviors. The electronic properties of the present compounds are analyzed by using the band structure and density of states. The phonon dispersion calculations imply that the present compounds are dynamically stable. Based on the quasi-harmonic approximation, the calculations of the specific heat indicate that the temperature in a range of 0 K–1500 K and pressure in a range of 0 GPa–40 GPa have a large effect on the thermal quantities of Ge_2N_2O,compared with on those of the C_2N_2O and Si_2N_2O compounds.
文摘Ab initio optimizations at HF /6-31G level and subsequent electrostatic potential calculations have been performed for a group of 68solvent mo lecules.Linear correlation of solv ent softness to the theoretical desc riptors has been established by using multiple r egression.The relationship can be well expressed as follows:D s =28.3844I-3.3965V min -10.9162Π+22.7684σ tot 2 +4.5040(N=65,R=0.960,R CV =0.953,SD =3.5557,F=175.66),and shows good predictie power.
基金the National Natural Science Foundation of China(Nos.50871035 and 51071061)the Program of Excellent Team at Harbin Institute of Technology
文摘The properties and electronic structure of Fe under pressures of 0-30GPa have been studied by flrst principles employing the density functional theory（DFT）,the ultra-soft pseudo-potentials（USPP）and the generalized gradient approximation（GGA）.The calculating results show that there is a structural transition from magnetic body-centered cubic（bcc）to nonmagnetic hexagonal-close-packed（hcp）structure for Fe around 11 GPa pressure.There is a pseudogap both in the density of states（DOS）for bcc and hcp Fe.The pseudogap of bcc Fe is deeper and wider than that of hcp Fe.The elastic modulus is obtained by Voigt-Reuss-Hill averaging scheme.The results indicate that the elastic properties of bcc Fe enhance with pressure except for elastic stiffness constant C11, shear modulus G and elastic modulus E at the transition pressure,while the elastic properties of hcp Fe increase linearly with pressure.Magnetic bcc Fe is ductile,and hcp Fe becomes ductile from brittle around 25 GPa.
文摘The low magnetic moment （MM） in diluted magnetic semiconductors （DMS） at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors （CMS）.This work reports an ab-initio investigation of the electronic structures and magnetic properties of ZnO in a zinc-blende （ZB） structure doped with nickel ions. Ni-doped ZnO-based DMS and CMS exhibit a dominance of ferromagnetic coupling over antiferromagnetic. A robust increase in the magnetization has been observed as a function of Ni impurity levels. This material favors short-range magnetic interactions at the ground state, suggesting that the observed ferromagnetism is defined by the double exchange mechanism. The spin-polarized density of states （DOS） of Ni-doped ZnO characterizes it as half-metallic with a considerable energy gap for up-spin components and as metallic for-down spins. Half metallic Ni：ZnO based magnetic semiconductors with high magnetization are expected to have potential applications in spintronics.
基金This work was supported by the National Natural Science Foundation of China(21971142,21973046 and 22271171).
文摘The reaction of DyCl_(3)·6H_(2)O with a rigid diacylhydrazone ligand(H_(2)L)afforded a trinuclear precursor[Dy_(3)L_(2)Cl_(3)(H_(2)O)_(2)(CH_(3)OH)]Cl_(2)·3CH_(3)OH(1).The replacement of the Cl-ions and the coordinating solvents by the aryloxides ligands(Lx)-yields three trinuclear complexes[Dy_(3)L_(2)(Lx)_(5)]·nsol(x=1,2-naphthol(2);x=2,7-hydroxycoumarin(3);and x=3,phenol(4)).In complexes 2-4,two end Dy^(3+)centers adopt almost identical N_(4)O_(4) coordination sphere of D6h geometry while the central one adopts N_(4)O_(5) coordination sphere in Cs geometry.Magnetic measurements reveal weak antiferromagnetic interactions in the hydrated samples 2e-4e and two-step slow relaxation process under zero dc field with effective energy barriers Ueff of 439 and 91 K,353 and 40 K,466 and 89 K for SR and FR in 2e-4e,respectively.Such dynamic magnetic behaviour for 4 persists in the magnetically diluted sample of 4@Y.Complex 4 possesses the short Dy-O_(aryloxide) bond distance of 2.055(18)Å,and the largest Ueff among the reported linear trinuclear dysprosium complexes.Moreover,the functionalized aryloxides ligands(Lx)-show photoluminescence via intramolecular energy transfer,making 2e-4e luminescent Dy^(3+)SMMs with high energy barriers.
