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Based on the combination of novel carbon material graphynes (GYs) and superalkalis (OM3), a class of GY superalkali complexes, OM3+@(GY/GDY/GTY)− (M = Li, Na, and K), has been designed and investigated using the density functional theory method. Computational results reveal that these complexes with high stability can be regarded as novel superalkali salts of GYs due to electron transfer from OM3 to GYs. For second‐order nonlinear optical response, these superalkali salts exhibit large first hyperpolarizabilities (β0). Two essential effects on β0 values are found, namely, the atomic number of alkali atom in superalkali and the pore size of GY. Integrating the two effects, the selected combination of OLi3 with large pore size graphtrigne (GTY) can lead to a considerable β0 value (6.5 × 105 au), which is a new record for superatom‐doped GYs. In the resulting complex, the OLi3 unit is located at the center of the pore of GTY, forming a planar structure with the highest stability among these salts. Besides large β0 values, these superalkali salts of GYs have a deep‐ultraviolet working region; hence, they can be considered a kind of high‐performance deep‐ultraviolet NLO molecule. [ABSTRACT FROM AUTHOR]

The heterodinuclear silver tetracarbonyl-iron anion was generated in the gas phase and studied by joint photoelectron velocity map imaging spectroscopy and quantum chemical calculations. The AgFe(CO)4− anion is characterized to be an 18-electron complex with the silver atom covalently bonded to the anionic tetracarbonyl-iron, an isolobal analogue of the methyl radical. The bonding analyses using a range of state-of-the-art quantum chemistry methods revealed a peculiar decentralized bonding situation, where the silver atom is covalently bonded to both the iron center and the vicinal carbon atoms in the form of an electron-sharing σ bond. [ABSTRACT FROM AUTHOR]

The average magnetic moment per atom of Mn13 cluster is expected to be enhanced by doping or coating with a shell. Several ternary core–shell icosahedral clusters TM@Mn12@Au20 were constructed by combining substituting the central Mn with VIII elements (Fe, Co, Ni, Ru, Rh, Pd and Pt) and coating with a icosahedral Au20 shell, and systematically studied by using the first-principles density functional method. Compared to Mn13, Fe@Mn12@Au20 cluster shows a giant enhancement on total magnetic moment (52 µB) which can be greatly attributed to the ferromagnetic coupling between spin moments of atoms. Coating with Au20 shell enlarged the average distances of TM-Mn and Mn-Mn and is a useful way to change the magnetic coupling style. By analysis of density of states and electron localisation functional, we can conclude that the weak hybridisation between Fe and Mn in Fe@Mn12@Au20 is propitious to maintain their original direction of spin moments of atoms and then form ferromagnetic coupling. [ABSTRACT FROM AUTHOR]

A Lewis structure corresponding to the most stable electron-localized state is often used as a reference for the measure of electron delocalization effect in the valence bond (VB) theory. As the simplest variant of ab initio VB theory, the generalized block-localized wavefunction (BLW) method defines the wavefunction for an electron-localized state with block-localized orbitals without the orthogonalization constraint on different blocks. The validity of the method can be critically examined with experimental evidences. Here the BLW method has been applied to the investigation of the roles of both the π conjugation and σ hyperconjugation effects in the conformational preference of formic acid for the trans (Z) conformer over the cis (E) conformer. On one hand, our computations showed that the deactivation of the π conjugation or σ hyperconjugation has little impact on the Z-E energy gap, thus neither is decisive and instead the local dipole-dipole electrostatic interaction between the carbonyl and hydroxyl groups is the key factor determining the Z-E energy gap. On the other hand, the present study supported the conventional view that π conjugation is largely responsible for the C-O rotation barrier in formic acid, though the existence of hyperconjugative interactions in the perpendicular structure lowers the barrier considerably. [ABSTRACT FROM AUTHOR]

Zn0.97Cu0.03O films were prepared by pulsed-laser deposition on c-cut sapphire substrates under various conditions in order to investigate the growth-dependent properties of the films. All the films exhibit room temperature ferromagnetism. Samples deposited at low temperature and low pressure show large saturation magnetization (Ms). Moreover, the enhancement of Ms was observed in films annealed both in vacuum and in Zn vapor. However, postannealing in air led to the remarkable reduction of ferromagnetism. The results show that the itinerant electrons introduced by oxygen-deficient or Zn-rich atmospheres may play a significant role in room temperature ferromagnetism observed in this ZnCuO dilute magnetic semiconductor. It is consistent with carrier-induced ferromagnetism. The magnetization strongly depends on the appearance of free carriers and is relatively insensitive to whether they arose from VO or/and Zni. [ABSTRACT FROM AUTHOR]

The Co-doped ZnO thin films were prepared on c-cut sapphire substrates by magnetron cosputtering, and then annealed at various temperatures in vacuum. Magnetic measurements indicate that all the films are ferromagnetic at room temperature and the magnetization of the annealed Zn0.88Co0.12O films is increased about one order of magnitude in comparison with the corresponding as-deposited one. The enhancement of magnetization is possibly due to the fact that the generation of oxygen vacancies during annealing in vacuum increases the carrier (electron) concentration, which is consistent with the mechanism of carrier-induced ferromagnetism. Optical spectrometry indicates that Co2+ enters the tetrahedral sites of the wurtzite structure of ZnO host and substitutes for Zn2+. [ABSTRACT FROM AUTHOR]

Second-order Moller-Plesset perturbation theory investigations indicate that the highly strained three- and four-membered semiconductor ring systems A[sub 3]R[sup +, sub 3], A[sub 2]BR[sup +, sub 3], GeSiCR[sup +, sub 3] A[sub 3]R[sub 3]Ha, and A[sub 4]R[sup 2+, sub 4] (A,B=C,Si,Ge; R=H, SiH[sub 3]; Ha=F, Cl, Br) exhibit aromaticities featured with the delocalized π orbitals perpendicular to the ring planes. [ABSTRACT FROM AUTHOR]

Structural optimizations and frequency analyses have been performed on free Ge[sup m-,sub n] and KGe[sup -,sub n] (n = 3-10, m = 2-4) Zintl anions and ionization potentials and electron affinities calculated for KGe[sub n] using the density functional theory (DFT) of Becke's three-parameter hybrid functional with the Perdew/Wang 91 expression. The DFT results obtained for small clusters (n = 3-5) are further checked with both the second-order Møller-Plesset perturbation theory (MP2) and the configuration interaction calculations with all single and double substitutions from the Hartree-Fock reference determinant (CISD). Free Ge[sup 2-,sub n] anions are found to share the same geometries as naked Zintl anions observed in solids with a systematical expansion in bond lengths within about 5%. Intensive searches indicate that two isomers, a tricapped trigonal prism (D[sub 3h]) and a slightly distorted tricapped trigonal prism (C[sub 2υ]), exist for Ge[sup 2-,sub 9] and Ge[sup 3-,sub 9], while nido-Ge[sup 4-,sub 9] clearly favors the monocapped antisquare prism (C[sub 4υ]) structure. HOMO-LUMO energy gaps >2.23 eV are obtained for Ge[sup m-,sub n] series at the DFT level, except Ge[sup 3-,sub 9] which has a much narrower energy gap of 1.16 eV. The calculated Gibbs free energy change of Ge[sup 2-,sub 9] + Ge[sup 4-,sub 9] = 2 Ge[sup 3-,sub 9] conversion reaction involving nonagermanides has the value of ΔG° = -2.91 × l0[sup 5] J mol[sup -1], providing the first quantum chemistry evidence that the geometrically deduced mixed valent couple of Ge[sup 2-,sub 9] and Ge[sup 4-,sub 9] in a previous study is thermodynamically unstable compared to two Ge[sup 3-,sub 9] anions. The calculated stabilization energies of Ge[sup 2-,sub n], Ge[sup -,sub n], and Ge[sub n] exhibit similar variation trends, clearly indicating a maximum at n = 7, a minimum at n = 8, and an obvious recovery at n = 9 and 10. The calculated normal vibrational... [ABSTRACT FROM AUTHOR]

Geometrical and electronic properties of Ge[sub n] (n=5–10) neutrals, cations, and anions have been investigated using the density functional method of Becke’s three-parameter hybrid functional with the Perdew/Wang 91 expression. Berny structural optimization and frequency analyses are performed with the basis of 6-311G(d) for both the neutrals and charged ions. Cohesive energies, ionization potentials, and electron affinities calculated at the optimized ground-state structures agree satisfactorily with recent experimental values. Frequency analyses indicate that the bicapped antitetragonal prism, which was previously proposed as the ground-state structure of Ge[sub 10][sup -], is in fact a first-order stationary point with an imaginary frequency at 95i (b[sub 2]). The optimized ground-state structure of Ge[sub 10][sup -] obtained in this work is a distorted, bicapped antitetragonal prism with the symmetry of C[sub 1]. It is a typical Jahn–Teller distortion. Prominent charge-induced structural changes are also determined for Ge[sub 5][sup +], Ge[sub 6][sup -], Ge[sub 7][sup +], Ge[sub 8][sup +], Ge[sub 8][sup -], and Ge[sub 9][sup -]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]