Zong-quan Gu

Theoretical calculation of the optical properties of Y3Fe5O12

The electronic structure and the optical properties of Y3Fe5O12 crystal are calculated using the local spin density approximation+U approach. The intra-atomic correlation effect of the Fe 3d electrons is shown to be important in describing the insulating nature of the crystal. With a choice of the parameters U=3.5 eV and J=0.8 eV in the model Hamiltonian, a gap of 2.66 eV is obtained and a significant lowering of the occupied potion of the Fe 3d states is observed. The calculated optical absorption in the range 3–6 eV is from the bulk O 2p to the Fe 3d band states. The calculated spin magnetic moments are in good agreement with experiment.

First-principles calculation of the electronic structure of yttrium iron garnet (Y3Fe5O12)

The electronic structure of Y3Fe5O12 (YIG) crystal was calculated using the spin-polarized orthogonalized linear combination of atomic orbitals method in the local spin-density approximation. It is shown that YIG has a ferrimagnetic ordering with Fe spin magnetic moments of −0.62μB and +1.56μB at the octahedral 16(a) site and the tetrahedral 24(d) site, respectively. The origin of ferrimagnetism in the two Fe sublattices can be traced to the different ordering of the eg and t2g levels for the spin-up and spin-down electrons.

Electronic structure of Nd2Fe14B

The electronic structure of Nd2Fe14B has been calculated using the first‐principle orthogonalized linear combination of atomic orbitals method. The f electrons in Nd are included in the calculation but are treated as localized states in the determination of the Fermi energy. Results are presented for the total density of states (DOS), orbital‐decomposed, and spin‐decomposed partial DOS. The calculated spin‐magnetic moments on each of the six Fe sites are in good agreement with the values deduced from the neutron scattering experiment. The charge density map and the spin density map on the basal plane of the tetragonal cell show the evidence for covalent bonding between Fe and B atoms and reveal the distortion from the spherically symmetric distribution around the atomic sites.

Magnetic moments of Co‐substituted Y2Fe14B

The local spin magnetic moments at each of the six inequivalent Fe sites in Y2Fe14B crystal are studied as the Fe atoms are selectively substituted by Co. First‐principles spin‐polarized electronic structure calculations are performed by the orthogonalized linear combination of atomic orbitals method and the spin magnetic moments are deduced from the site‐projected and spin‐projected partial density of states. In general, a Co substituted site has a smaller moment than the same site in Y2Co14B. The unsubstituted Fe sites are almost unchanged. The c, j2, and j1 sites are affected most while the e site is least affected by the Co substitution.

Electronic structure of microporous titanosilicate ETS-10

Abstract The electronic structure of a microporous titanosilicate framework, ETS-10 is calculated by means of a first-principles self-consistent method. It is shown that without the inclusion of the alkali atoms whose positions in the framework are unknown, ETS-10 is an electron deficient system with 32 electrons per unit cell missing at the top of an otherwise semiconductor-like band structure. The calculated density of states are resolved into partial components. It is shown that the states of the missing electrons primarily originate from the Ti—O bond. The local density of states of the Ti-3d orbitals in the ETS-10 framework is quite different from the perovskite BaTiO3. The possibilities of ETS-10 crystal being ferroelectric or having other interesting properties are discussed.

Electronic structure of Nd2Fe17N

The electronic structures of ternary compound Nd2Fe17N with N atoms on 9e, 3b, and 18g sites are calculated and compared. The local moments on different Fe sites are in good agreement with experiments. The mechanism of increasing Curie temperature by N doping is checked by additional calculations with lattice expansion. The results show that the change in interatomic interaction is more important than the lattice expansion effect.The electronic structure of Nd/sub 2/Fe/sub 14/B has been calculated using the first-principles orthogonalized linear combination of atomic orbitals method. The f electrons in Nd are included in the calculation but are treated as localized states in the determination of the Fermi energy. Results are presented for the total density of states (DOS), orbital-decomposed and spin-decomposed partial DOS. The calculated spin-magnetic moments on each of the six Fe sites are in good agreement with the values deduced from neutron scattering experiment. The charge density map and the spin density map on the basal plane of the tetragonal cell show the evidence for covalent bonding between Fe and B atoms and reveal the distortion from the spherically symmetric distribution around the atomic sites.

Electronic structure and spin density of Gd2Fe14B

The electronic structure of Gd2Fe14B has been calculated using the spin‐polarized orthogonalized linear combination of atomic orbitals method. The use of the band approach to study the magnetic properties of the rare‐earth iron‐boron compounds should be more valid in the case of Gd2Fe14B because of the exactly half‐filled f shell of the Gd atom, which has a zero orbital angular momentum. The calculated total spin magnetic moment of 18.41 μB per formula unit is in good agreement with experiment, and the site‐decomposed Fe moments show that the j2 site has the highest and the e site has the smallest moment. Other results presented include total and partial density of states and the spin density distributions on the basal and [110] plane. The positive spin density from the Fe sites shows a network type of structure parallel to the c axis. These and other results are compared with those calculated for Nd2Fe14B.

Electronic structure and Fe moment distribution in Nd5Fe17

The electronic structure and the Fe moment distribution in Nd5Fe17 are calculated using the first-principles orthogonalized linear combination of atomic orbitals method. It is shown that there is no obvious correlation of the Fe moment with the nearest neighbor Fe–Fe separations. There is a reasonable correlation with the number of nearest Fe neighbors, NNN except for NNN=12. When the averaged Fe moments within the same group of Fe atoms of same NNN are plotted against the average Fe–Fe distances, the results are in good agreement with similar data derived from neutron diffraction analysis. The calculated total moment per formula unit and the average Fe moment are also in good agreement with experimental values.