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In this paper, the second and third order polarizabilities of small GanAsm (n+m=4–10) clusters are systematically investigated using the time dependent density functional theory (TDDFT)/6-311+G* combined with the sum-over-states method (SOS//TDDFT/6-311+G*). For the static second order polarizabilities, the two-level term (βvec.2) makes a significant contribution to the βvec for all considered GanAsm clusters except for the Ga3As4 cluster. And, for the static third order polarizabilities, the positive channel (<γ>II) makes a larger contribution to 〈γ〉tot than the negative channel (<γ>I). Similar to the cubic GaAs bulk materials, the small GanAsm cluster assembled materials exhibit large second order (1×10-6 esu) and third order susceptibilities (5×10-11 esu). The dynamic behavior of β(-2ω;ω,ω) and γ(-3ω;ω,ω,ω) show that the small GanAsm cluster will be a good candidate of nonlinear optical materials due to the avoidance of linear resonance photoabsorption. [ABSTRACT FROM AUTHOR]

We report the band structures as well as frequency-dependent (dynamic) linear and nonlinear optical properties of CsCdBr3 and RbCdI3·H2O crystals calculated within density functional theory with a nonlocal gradient correction, including the dielectric function, linear and nonlinear refractive indices, frequency doubling, and self-focusing of light. The electronic origin of the optical susceptibilities is described and the critical power of light self-focusing is estimated for these two crystals. [ABSTRACT FROM AUTHOR]

Configuration optimizations, excited state properties, and the frequency-dependent third-order nonlinear optical polarizabilities have been investigated on a series of methyl-silsesquioxane (MeT) cages [CH3SiO1.5]n (n=4, 6, 8, and 10) using ab initio quantum mechanical methods coupled with the sum-over-states methods. The obtained electronic absorption spectra show a redshift as the cage size increases, and the absorption spectra are assigned as charge transfers from oxygen p type to silicon s type atomic orbitals. The calculated average third-order polarizabilities of 〈γ〉 in the three optical physical processes (third-harmonic generation, the electric-field-induced second-harmonic generation, and degenerate four-wave mixing) have wide nonresonance regions. For all the considered species, the values of γ decrease in the order of [MeT]4>[MeT]8(C2v)=[MeT]10>[MeT]6>[MeT]8(Oh). [ABSTRACT FROM AUTHOR]

Using the ab initio method, the geometrical structures of C36 and the X (B,N)-doped isomers C34X2 have been optimized. On the basis of the optimized structures, then, the third-order nonlinear optical polarizabilities γ in the different optical processes of the third-harmonic generation, electric-field induced second-harmonic generation and degenerate four-wave mixing, and two-photon absorption (TPA) cross sections δ are calculated by using TDB3LYP method coupled with the sum-over-states method. The calculated results show that the one-photon allowed excitation process dominate the two-photon excitation process for C36-D6h, whereas the two-photon allowed excitation process dominate the one-photon excitation process for C36-D2d and C34X2 (B,N). It is found that the largest resonant TPA peaks of dopant fullerenes have a blueshift and the TPA cross sections have an enhancement compared with those of the parent fullerenes of isomers C36-D6h and C36-D2d. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Spin multiplicity enhancements of third-order nonlinear polarizabilities have been investigated at the excited state for finite single-walled carbon nanotubes (5,0) and (6,0) in terms of the time-dependent density functional theory combined with the sum-over-states method. The time-dependent density functional theory at the B3LYP/3-21G level is employed to calculate the transition moments and the excited state energies of optimized tubes. The obtained results show that the third-order polarizabilities of γ at the excited triplet state are enhanced about from 2 to 3 orders of magnitude and the estimated third-order optical susceptibility of χ[sup (3)] is as large as 10[sup -8] esu magnitude order. The electron transitions among the three triplet states make significant contributions to third-order polarizabilities of the (5,0) nanotube, and the electron transition between the two triplet states makes main the contribution to those of the (6,0) nanotube. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The maximized geometrical compositions and characteristics of stimulated phases using time-dependent density functional theory are reported. The computed dynamic polarizabilities of all three processes show diverse patterns at a nonresonant frequency.

Abstract: In this paper, we have calculated the third-order nonlinear optical polarizabilities corresponding to three optical processes: third-harmonic generation (THG), electric-field-induced second-harmonic generation (EFISHG) and degenerate four-wave mixing (DFWM) for B12N12, B24N24 and B36N36 clusters. The calculations have been performed by employing ab initio time-dependent density functional theory combined with sum-over-states method (SOS//TDDFT). We obtained the similar dynamic behavior of third-order NLO polarizabilities for three BN clusters. At input photon energy below 1.25eV, the resonance enhancements of response haven''t occurred. This is due to the fact that the calculated BN clusters have the large transition energy. B24N24 cluster has the larger transition dipole moments and the third-order polarizabilities of B24N24 are much larger than those of B12N12 and B36N36. We also estimate the static third-order optical susceptibility χ (3) for BN fullerene materials from the average static third-order polarizability <γ>. The static χ (3) of B24N24 fullerene materials are 1.36×10−14 esu for three NLO processes. [Copyright &y& Elsevier]

We employ an ab initio time-dependent Hartree–Fock (TDHF) formalism combined with sum-over-states (SOS) method to calculate the linear and nonlinear optical properties of direct semiconductor clusters. The obtained electronic absorption spectra predict a variety of the spectral shapes and peak positions and an increase of the second-order nonlinear optical response with an increase of V-group ionic radius in the title clusters. Charge transfers from the π bonding to π antibonding orbitals between III and V group atoms make a significant contribution to the second-order polarizability. [Copyright &y& Elsevier]

An ever increasing demand for zinc has resulted in worldwide efforts to exploit complex and lean grade reserves of zinc oxide ore. In the present study, experiments were conducted on zinc recovery from high fluorine bearing zinc oxide ore. First, the effect of different variables on fluorine removal was investigated. Optimum experimental conditions occurred when the temperature was 1173 K, roasting time was 90 min and air flow was at a velocity of 6 m min-1; the fluorine removal from the samples reached over 93%. The results obtained indicate that fluorine removal is not enhanced by adding diluted sulphuric acid or water as a binder. Second, the roasted materials were leached with a diluted sulphuric acid, and then neutralised, flocculated and finally filtrated. The residual fluorine content in the leached solutions was <38 mg L-1, which satisfies the requirement of fluorine content in the leached solutions for the production of electrolytic zinc. [ABSTRACT FROM AUTHOR]

We report the dispersion of the optical Kerr effect and the wavelength-dependent critical power of light self-focusing for semiconductors CdxHg1-xGa2S4 in view of the calculated results from the density functional theory combined with an anharmonic oscillator model. It is shown that the third-order optical properties are controlled by the band gaps or cation contents of CdxHg1-xGa2S4, and it is indicated that the optical Kerr effect decreases and the critical power of light self-focusing increases as the x contents and band gaps increase for CdxHg1-xGa2S4. [ABSTRACT FROM AUTHOR]

Abstract: Configurations of four [5, 6]-open C60 monoadducts have been optimized at B3LYP/6-31G* level. The calculated geometrical structures show that the bonds at the junction between five- and six-membered rings break and the planar properties of pentagon and hexagon rings in the vicinity of functionalized groups disappear for these C60 derivatives. On the basis of the optimized geometrical structures, their excitation energies and third-order nonlinear optical polarizabilities have been calculated at TDB3LYP/3-21G* level coupled with sum-over-states method for these C60 monoadducts. The obtained results show that different functionalized groups result in different effects on HOMO–LUMO gap and different optical property for [5, 6]-open C60 derivatives. The absorption spectra of the derivatives, in which a nitrogen atom bridges the functionalized groups to C60 cage, show a red shift compared with those of the derivatives in which a carbon atom becomes as the connection. [Copyright &y& Elsevier]

Configurations of C60 fullerene derivatives (C60COOCH2, C60COOHCH3) are optimized using B3LYP method at 6–31G* level. The calculated charge distributions by Natural Population Analysis show that the charge transfers exist between the functionalized group and parent C60. Then, the excited state properties of title species are calculated by the time-dependent density functional theory. It is shown that the fullerene derivatives make a small red shift of the absorption spectra in comparison with the C60 cage itself and the calculated electronic absorption spectra are in good agreements with their observed values. [Copyright &y& Elsevier]

We report the dispersion of the optical Kerr effect and the wavelength-dependent critical power of light self-focusing for semiconductors CdxHg1-xGa2S4 in view of the calculated results from the density functional theory combined with an anharmonic oscillator model. It is shown that the third-order optical properties are controlled by the band gaps or cation contents of CdxHg1-xGa2S4, and it is indicated that the optical Kerr effect decreases and the critical power of light self-focusing increases as the x contents and band gaps increase for CdxHg1-xGa2S4. [ABSTRACT FROM AUTHOR]

In this paper, the second and third order polarizabilities of small Ga(n)As(m) (n + m=4-10) clusters are systematically investigated using the time dependent density functional theory (TDDFT)6-311+G* combined with the sum-over-states method (SOSTDDFT6-311+G*). For the static second order polarizabilities, the two-level term (beta(vec.2)) makes a significant contribution to the beta(vec) for all considered Ga(n)As(m) clusters except for the Ga3As4 cluster. And, for the static third order polarizabilities, the positive channel (gamma(II)) makes a larger contribution to gamma(tot) than the negative channel (gamma(I)). Similar to the cubic GaAs bulk materials, the small Ga(n)As(m) cluster assembled materials exhibit large second order (1 x 10(-6) esu) and third order susceptibilities (5 x 10(-11) esu). The dynamic behavior of beta(-2omega; omega, omega) and gamma(-3omega; omega, omega, omega) show that the small Ga(n)As(m) cluster will be a good candidate of nonlinear optical materials due to the avoidance of linear resonance photoabsorption.

Using the ab initio method, the geometrical structures of C(36) and the X (B,N)-doped isomers C(34)X(2) have been optimized. On the basis of the optimized structures, then, the third-order nonlinear optical polarizabilities gamma in the different optical processes of the third-harmonic generation, electric-field induced second-harmonic generation and degenerate four-wave mixing, and two-photon absorption (TPA) cross sections delta are calculated by using TDB3LYP method coupled with the sum-over-states method. The calculated results show that the one-photon allowed excitation process dominate the two-photon excitation process for C(36)-D(6h), whereas the two-photon allowed excitation process dominate the one-photon excitation process for C(36)-D(2d) and C(34)X(2) (B,N). It is found that the largest resonant TPA peaks of dopant fullerenes have a blueshift and the TPA cross sections have an enhancement compared with those of the parent fullerenes of isomers C(36)-D(6h) and C(36)-D(2d).