The generalized successive overrelaxation （GSOR） method was presented and studied by Bai, Parlett and Wang [Numer. Math. 102（2005）, pp.1-38] for solving the augmented system of linear equations, and the optimal it...The generalized successive overrelaxation （GSOR） method was presented and studied by Bai, Parlett and Wang [Numer. Math. 102（2005）, pp.1-38] for solving the augmented system of linear equations, and the optimal iteration parameters and the corresponding optimal convergence factor were exactly obtained. In this paper, we further estimate the contraction and the semi-contraction factors of the GSOR method. The motivation of the study is that the convergence speed of an iteration method is actually decided by the contraction factor but not by the spectral radius in finite-step iteration computations. For the nonsingular augmented linear system, under some restrictions we obtain the contraction domain of the parameters involved, which guarantees that the contraction factor of the GSOR method is less than one. For the singular but consistent augmented linear system, we also obtain the semi-contraction domain of the parameters in a similar fashion. Finally, we use two numerical examples to verify the theoretical results and the effectiveness of the GSOR method.展开更多
The electronic density of states and band structures of doped and un-doped anatase TiO2 were studied by the Linearized Augmented Plane Wave method based on the density functional theory. The calculation shows that the...The electronic density of states and band structures of doped and un-doped anatase TiO2 were studied by the Linearized Augmented Plane Wave method based on the density functional theory. The calculation shows that the band structures of TiO2 crystals doped with transition metal atoms become narrower. Interesting, an excursion towards high energy level with increasing atomic number in the same element period could be observed after doping with transition metal atoms.展开更多
The electronic structures and magnetism of Fe nanowires along the [110] direction on Cu（001） and Ag（001） [Fe（nw）/Cu（001） and Fe（nw）/Ag（001）] are investigated by using the all-electron full-potential linear...The electronic structures and magnetism of Fe nanowires along the [110] direction on Cu（001） and Ag（001） [Fe（nw）/Cu（001） and Fe（nw）/Ag（001）] are investigated by using the all-electron full-potential linearized augmented plane wave method in the generalized gradient approximation. It is found that the magnetic moment of Fe atom for the Fe（nw）/Cu（001） is 2.99#B, which is slightly smaller than that （3.02μB） for the Fe（nw）/Ag（001） but much larger than that （2.22μB） for the bcc iron. The great enhancement of magnetic moment in the Fe nanowires can be explained by the Fe d-band narrowing and enhancement of the spin-splitting due to a reduction in coordination number, From the calculated spin-polarized layer-projected density of states, it is found that the Fe 3d-states are strongly hybridized with the adjacent Cu 3d-states in the Fe（nw）/Cu（001）, and there exists a strong hybridization between the Fe sp-and the adjacent Ag 4d-states in the Fe（nw）/Ag（001）.展开更多
This paper investigates the effect of atomic disorder on the electronic structure, magnetism, and half-metallicity of full-Heusler Co2FeSi alloy by using the full-potential linearized augmented plane wave method withi...This paper investigates the effect of atomic disorder on the electronic structure, magnetism, and half-metallicity of full-Heusler Co2FeSi alloy by using the full-potential linearized augmented plane wave method within the generalized gradient approximation （GGA） and GGA-kU schemes. It considers three types of atomic disorders in Co2FeSi alloy： the Co-Fe, Co-Si, and Fe-Si disorders. Total energy calculations show that of the three types of disorders, the Fe-Si disorder is more likely to occur. It finds that for the Co Si disorder, additional states appear in the minority band-gap at the EF and the half-metallcity is substantially destroyed, regardless of the disorder level. On the other hand, the Co-Fe and Fe-Si disorders have little effect on the half-metallicity at a low disorder level. When increasing the disorder levels, the half-metallcity is destroyed at about 9 % of the Co-Fe disorder level, while that stays at 25 % of the Fe-Si disorder level.展开更多
The effect of Cd impurity on the electronic structure and magnetic properties of hydrogen-terminated AlN nanoribbons with zigzag edges （ZAINNRs） was in- vestigate using the band structure results obtained through th...The effect of Cd impurity on the electronic structure and magnetic properties of hydrogen-terminated AlN nanoribbons with zigzag edges （ZAINNRs） was in- vestigate using the band structure results obtained through the full potential linearized augmented plane wave （FP- LAPW） method within the density functional theory （DFT）. The exchange correlation potential was treated by the generalized gradient approximation within the Perdew scheme. The calculated results show that the H-terminated zigzag AlN nanoribbon is semiconducting and nonmag- netic material with a direct band gap of about 2.78 eV, while the Cd-doped H-terminated ZAlNNR structures show complete （100 %） spin polarization very close to the Fermi level, which will result in spin-anisotropic transport. The charge transport is totally dominated by Cd spin down electrons in the H-terminated ZAlNNR. These results suggest potential applications for the development of using the A1N nanoribbons in nanoelectronics and magnetoelec-tronic devices as a base.展开更多
Local density functional is investigated by using the full-potential linearized augmented plane wave （FP-LAPW） method for ScN in the hexagonal structure and the rocksalt structure and for hexagonal structures linkin...Local density functional is investigated by using the full-potential linearized augmented plane wave （FP-LAPW） method for ScN in the hexagonal structure and the rocksalt structure and for hexagonal structures linking a layered hexagonal phase with wurtzite structure along a homogeneous strain transition path. It is found that the wurtzite ScN is unstable and the layered hexagonal phase, labelled as ho, in which atoms are approximately fivefold coordinated, is metastable, and the rocksalt ScN is stable. The electronic structure, the physical properties of the intermediate structures and the energy band structure along the transition are presented. It is found that the band gaps change from 4.0 to 1.0 eV continuously when c/a value varies from 1.68 to 1.26. It is noticeable that the study of ScN provides an opportunity to apply this kind of material （in wurtzite[h]-derived phase）.展开更多
In this paper, we investigated the structural, electronic and optical properties of InAs, InN and InP binary compounds and their related ternary and quaternary alloys by using the full potential linearized augmented p...In this paper, we investigated the structural, electronic and optical properties of InAs, InN and InP binary compounds and their related ternary and quaternary alloys by using the full potential linearized augmented plane wave（FP-LAPW）method based on density functional theory（DFT）. The total energies, the lattice parameters, and the bulk modulus and its first pressure derivative were calculated using different exchange correlation approximations. The local density approach（LDA） and Tran–Blaha modified Becke–Johnson（TB-m BJ） approximations were used to calculate the band structure.Nonlinear variations of the lattice parameters, the bulk modulus and the band gap with compositions x and y are found.Furthermore, the optical properties and the dielectric function, refractive index and loss energy were computed. Our results are in good agreement with the validated experimental and theoretical data found in the literature.展开更多
First-principles calculations by means of the full-potential linearized augmented plane wave method using the generalized gradient approximation with correlation effect correction（GGA＋U） within the framework of spi...First-principles calculations by means of the full-potential linearized augmented plane wave method using the generalized gradient approximation with correlation effect correction（GGA＋U） within the framework of spin polarized density functional theory（DFT＋U） are used to study the structural,electronic,and magnetic properties of cubic perovskite compounds RbXF3（X = Mn,V,Co,and Fe）.It is found that the calculated structural parameters,i.e.,lattice constant,bulk modulus,and its pressure derivative are in good agreement with the previous results.Our results reveal that the strong spin polarization of the 3d states of the X atoms is the origin of ferromagnetism in RbXF3.Cohesive energies and the magnetic moments of RbXF3 have also been calculated.The calculated electronic properties show the half-metallic nature of RbCoF3 and RbFeF3,making these materials suitable for spintronic applications.展开更多
The adaptively compressed exchange(ACE)operator is a low-rank representation of the Fock exchange,avoiding any loss of precision.We present an application of this method in the formalism of linearized augmented plane ...The adaptively compressed exchange(ACE)operator is a low-rank representation of the Fock exchange,avoiding any loss of precision.We present an application of this method in the formalism of linearized augmented plane waves(LAPW)to hybrid functionals with range separation.For this purpose,we extend the functionality of the LAPW-specific Poisson solver employing the pseudocharge method for the short-and long-range interaction kernels.To make these calculations more affordable,we revise the most expensive steps in the pseudocharge method and reduce their computational complexity.As a result,this implementation is a first step towards cubic-scaling hybrid calculations employing LAPW with respect to the number of atoms.We apply our code for assessing the numerical quality of band gaps computed with hybrid functionals in the literature,employing a test set consisting of 26 materials.展开更多
基金supported by State Key Laboratory of Scientific/Engineering Computing,Chinese Academy of SciencesThe National Key Basic Research Program of China (973 program) under Grant 2005CB321701+2 种基金The National Natural Science Foundation (No. 10771168)The Natural Science and Technology Development Plan Research Project of Shaanxi Province (No. 2008K01-33)The Special Plan Research Project of Shaanxi Education Department (No. 09JK716),P.R.China
文摘The generalized successive overrelaxation （GSOR） method was presented and studied by Bai, Parlett and Wang [Numer. Math. 102（2005）, pp.1-38] for solving the augmented system of linear equations, and the optimal iteration parameters and the corresponding optimal convergence factor were exactly obtained. In this paper, we further estimate the contraction and the semi-contraction factors of the GSOR method. The motivation of the study is that the convergence speed of an iteration method is actually decided by the contraction factor but not by the spectral radius in finite-step iteration computations. For the nonsingular augmented linear system, under some restrictions we obtain the contraction domain of the parameters involved, which guarantees that the contraction factor of the GSOR method is less than one. For the singular but consistent augmented linear system, we also obtain the semi-contraction domain of the parameters in a similar fashion. Finally, we use two numerical examples to verify the theoretical results and the effectiveness of the GSOR method.
文摘The electronic density of states and band structures of doped and un-doped anatase TiO2 were studied by the Linearized Augmented Plane Wave method based on the density functional theory. The calculation shows that the band structures of TiO2 crystals doped with transition metal atoms become narrower. Interesting, an excursion towards high energy level with increasing atomic number in the same element period could be observed after doping with transition metal atoms.
文摘The electronic structures and magnetism of Fe nanowires along the [110] direction on Cu（001） and Ag（001） [Fe（nw）/Cu（001） and Fe（nw）/Ag（001）] are investigated by using the all-electron full-potential linearized augmented plane wave method in the generalized gradient approximation. It is found that the magnetic moment of Fe atom for the Fe（nw）/Cu（001） is 2.99#B, which is slightly smaller than that （3.02μB） for the Fe（nw）/Ag（001） but much larger than that （2.22μB） for the bcc iron. The great enhancement of magnetic moment in the Fe nanowires can be explained by the Fe d-band narrowing and enhancement of the spin-splitting due to a reduction in coordination number, From the calculated spin-polarized layer-projected density of states, it is found that the Fe 3d-states are strongly hybridized with the adjacent Cu 3d-states in the Fe（nw）/Cu（001）, and there exists a strong hybridization between the Fe sp-and the adjacent Ag 4d-states in the Fe（nw）/Ag（001）.
基金supported by the National Natural Science Foundation of China (Grant No 10664005)
文摘This paper investigates the effect of atomic disorder on the electronic structure, magnetism, and half-metallicity of full-Heusler Co2FeSi alloy by using the full-potential linearized augmented plane wave method within the generalized gradient approximation （GGA） and GGA-kU schemes. It considers three types of atomic disorders in Co2FeSi alloy： the Co-Fe, Co-Si, and Fe-Si disorders. Total energy calculations show that of the three types of disorders, the Fe-Si disorder is more likely to occur. It finds that for the Co Si disorder, additional states appear in the minority band-gap at the EF and the half-metallcity is substantially destroyed, regardless of the disorder level. On the other hand, the Co-Fe and Fe-Si disorders have little effect on the half-metallicity at a low disorder level. When increasing the disorder levels, the half-metallcity is destroyed at about 9 % of the Co-Fe disorder level, while that stays at 25 % of the Fe-Si disorder level.
基金financially supported by the Research of the Ayatollah Alozma Boroujerdi University(No. 92-1012)
文摘The effect of Cd impurity on the electronic structure and magnetic properties of hydrogen-terminated AlN nanoribbons with zigzag edges （ZAINNRs） was in- vestigate using the band structure results obtained through the full potential linearized augmented plane wave （FP- LAPW） method within the density functional theory （DFT）. The exchange correlation potential was treated by the generalized gradient approximation within the Perdew scheme. The calculated results show that the H-terminated zigzag AlN nanoribbon is semiconducting and nonmag- netic material with a direct band gap of about 2.78 eV, while the Cd-doped H-terminated ZAlNNR structures show complete （100 %） spin polarization very close to the Fermi level, which will result in spin-anisotropic transport. The charge transport is totally dominated by Cd spin down electrons in the H-terminated ZAlNNR. These results suggest potential applications for the development of using the A1N nanoribbons in nanoelectronics and magnetoelec-tronic devices as a base.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB605102)
文摘Local density functional is investigated by using the full-potential linearized augmented plane wave （FP-LAPW） method for ScN in the hexagonal structure and the rocksalt structure and for hexagonal structures linking a layered hexagonal phase with wurtzite structure along a homogeneous strain transition path. It is found that the wurtzite ScN is unstable and the layered hexagonal phase, labelled as ho, in which atoms are approximately fivefold coordinated, is metastable, and the rocksalt ScN is stable. The electronic structure, the physical properties of the intermediate structures and the energy band structure along the transition are presented. It is found that the band gaps change from 4.0 to 1.0 eV continuously when c/a value varies from 1.68 to 1.26. It is noticeable that the study of ScN provides an opportunity to apply this kind of material （in wurtzite[h]-derived phase）.
基金supported by the Deanship of Scientific Research at King Saud University Group(Grant No.PRG-1437-39)
文摘In this paper, we investigated the structural, electronic and optical properties of InAs, InN and InP binary compounds and their related ternary and quaternary alloys by using the full potential linearized augmented plane wave（FP-LAPW）method based on density functional theory（DFT）. The total energies, the lattice parameters, and the bulk modulus and its first pressure derivative were calculated using different exchange correlation approximations. The local density approach（LDA） and Tran–Blaha modified Becke–Johnson（TB-m BJ） approximations were used to calculate the band structure.Nonlinear variations of the lattice parameters, the bulk modulus and the band gap with compositions x and y are found.Furthermore, the optical properties and the dielectric function, refractive index and loss energy were computed. Our results are in good agreement with the validated experimental and theoretical data found in the literature.
文摘First-principles calculations by means of the full-potential linearized augmented plane wave method using the generalized gradient approximation with correlation effect correction（GGA＋U） within the framework of spin polarized density functional theory（DFT＋U） are used to study the structural,electronic,and magnetic properties of cubic perovskite compounds RbXF3（X = Mn,V,Co,and Fe）.It is found that the calculated structural parameters,i.e.,lattice constant,bulk modulus,and its pressure derivative are in good agreement with the previous results.Our results reveal that the strong spin polarization of the 3d states of the X atoms is the origin of ferromagnetism in RbXF3.Cohesive energies and the magnetic moments of RbXF3 have also been calculated.The calculated electronic properties show the half-metallic nature of RbCoF3 and RbFeF3,making these materials suitable for spintronic applications.
基金supported by the European Union's Horizon 2020 research and innovation program under the grant agreement No.951786(NOMAD CoE)the Latvian Quantum Initiative within European Union Recovery and Resilience Facility project No.2.3.1.1.i.0/1/22/I/CFLA/001.We also acknowledge the EuroHPC Joint Undertaking for awarding access to the EuroHPC supercomputer LUMI,hosted by CSC(Finland)and the LUMI consortium through a EuroHPC Development Access call.
文摘The adaptively compressed exchange(ACE)operator is a low-rank representation of the Fock exchange,avoiding any loss of precision.We present an application of this method in the formalism of linearized augmented plane waves(LAPW)to hybrid functionals with range separation.For this purpose,we extend the functionality of the LAPW-specific Poisson solver employing the pseudocharge method for the short-and long-range interaction kernels.To make these calculations more affordable,we revise the most expensive steps in the pseudocharge method and reduce their computational complexity.As a result,this implementation is a first step towards cubic-scaling hybrid calculations employing LAPW with respect to the number of atoms.We apply our code for assessing the numerical quality of band gaps computed with hybrid functionals in the literature,employing a test set consisting of 26 materials.
